+publisher:"University of Texas – Austin" +contributor:("Moser, Robert deLancey")

University of Texas – Austin

1. Ulerich, Rhys David. Reducing turbulence- and transition-driven uncertainty in aerothermodynamic heating predictions for blunt-bodied reentry vehicles.

Degree: PhD, Computational Science, Engineering, and Mathematics, 2014, University of Texas – Austin

URL: http://hdl.handle.net/2152/26886

► Turbulent boundary layers approximating those found on the NASA Orion Multi-Purpose Crew Vehicle (MPCV) thermal protection system during atmospheric reentry from the International Space Station… (more)

▼ Turbulent boundary layers approximating those found on the NASA Orion Multi-Purpose Crew Vehicle (MPCV) thermal protection system during atmospheric reentry from the International Space Station have been studied by direct numerical simulation, with the ultimate goal of reducing aerothermodynamic heating prediction uncertainty. Simulations were performed using a new, well-verified, openly available Fourier/B-spline pseudospectral code called Suzerain equipped with a ``slow growth'' spatiotemporal homogenization approximation recently developed by Topalian et al. A first study aimed to reduce turbulence-driven heating prediction uncertainty by providing high-quality data suitable for calibrating Reynolds-averaged Navier – Stokes turbulence models to address the atypical boundary layer characteristics found in such reentry problems. The two data sets generated were Ma[approximate symbol] 0.9 and 1.15 homogenized boundary layers possessing Re[subscript theta, approximate symbol] 382 and 531, respectively. Edge-to-wall temperature ratios, T[subscript e]/T[subscript w], were close to 4.15 and wall blowing velocities, v[subscript w, superscript plus symbol]= v[subscript w]/u[subscript tau], were about 8 x 10-3 . The favorable pressure gradients had Pohlhausen parameters between 25 and 42. Skin frictions coefficients around 6 x10-3 and Nusselt numbers under 22 were observed. Near-wall vorticity fluctuations show qualitatively different profiles than observed by Spalart (J. Fluid Mech. 187 (1988)) or Guarini et al. (J. Fluid Mech. 414 (2000)). Small or negative displacement effects are evident. Uncertainty estimates and Favre-averaged equation budgets are provided. A second study aimed to reduce transition-driven uncertainty by determining where on the thermal protection system surface the boundary layer could sustain turbulence. Local boundary layer conditions were extracted from a laminar flow solution over the MPCV which included the bow shock, aerothermochemistry, heat shield surface curvature, and ablation. That information, as a function of leeward distance from the stagnation point, was approximated by Re[subscript theta], Ma[subscript e], [mathematical equation], v[subscript w, superscript plus sign], and T[subscript e]/T[subscript w] along with perfect gas assumptions. Homogenized turbulent boundary layers were initialized at those local conditions and evolved until either stationarity, implying the conditions could sustain turbulence, or relaminarization, implying the conditions could not. Fully turbulent fields relaminarized subject to conditions 4.134 m and 3.199 m leeward of the stagnation point. However, different initial conditions produced long-lived fluctuations at leeward position 2.299 m. Locations more than 1.389 m leeward of the stagnation point are predicted to sustain turbulence in this scenario. Advisors/Committee Members: Moser, Robert deLancey (advisor).

Subjects/Keywords: Atmospheric reentry; B-spline collocation; Channel flow; Cold wall; Direct numerical simulation; Energy perturbation method; Favorable pressure gradient; Flat plate; Homogenized boundary layer; Inviscid base flow; Isothermal wall; Low Reynolds number; Manufactured solution; NASA Orion; Negative displacement thickness; Predictive computation; Pseudospectral method; Radial nozzle; Reducing uncertainty; Reentry vehicle; Relaminarization; Sampling uncertainty; Simulation framework; Slow growth formulation; Software verification; Transition modeling; Turbulence budgets; Turbulent boundary layer; Wall blowing; Wall transpiration

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Ulerich, R. D. (2014). Reducing turbulence- and transition-driven uncertainty in aerothermodynamic heating predictions for blunt-bodied reentry vehicles. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/26886

Chicago Manual of Style (16^th Edition):

Ulerich, Rhys David. “Reducing turbulence- and transition-driven uncertainty in aerothermodynamic heating predictions for blunt-bodied reentry vehicles.” 2014. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/26886.

MLA Handbook (7^th Edition):

Ulerich, Rhys David. “Reducing turbulence- and transition-driven uncertainty in aerothermodynamic heating predictions for blunt-bodied reentry vehicles.” 2014. Web. 07 Mar 2021.

Vancouver:

Ulerich RD. Reducing turbulence- and transition-driven uncertainty in aerothermodynamic heating predictions for blunt-bodied reentry vehicles. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2014. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/26886.

Council of Science Editors:

Ulerich RD. Reducing turbulence- and transition-driven uncertainty in aerothermodynamic heating predictions for blunt-bodied reentry vehicles. [Doctoral Dissertation]. University of Texas – Austin; 2014. Available from: http://hdl.handle.net/2152/26886

2. Jee, Sol Keun, 1979-. Computer simulation of blood flow in microvessels and numerical experiments on a cell-free layer.

Degree: MSin Engineering, Mechanical Engineering, 2007, University of Texas – Austin

URL: http://hdl.handle.net/2152/16258

► Simulating blood flow in microvessels is a major challenge because of the numerous blood cells suspended in the blood. Furthermore, red blood cells (RBCs), which… (more)

Subjects/Keywords: Blood flow; Simulation; Microvessels; Cell-free layer; Cells; Deformable red blood cells

9 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Jee, Sol Keun, 1. (2007). Computer simulation of blood flow in microvessels and numerical experiments on a cell-free layer. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/16258

Chicago Manual of Style (16^th Edition):

Jee, Sol Keun, 1979-. “Computer simulation of blood flow in microvessels and numerical experiments on a cell-free layer.” 2007. Masters Thesis, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/16258.

MLA Handbook (7^th Edition):

Jee, Sol Keun, 1979-. “Computer simulation of blood flow in microvessels and numerical experiments on a cell-free layer.” 2007. Web. 07 Mar 2021.

Vancouver:

Jee, Sol Keun 1. Computer simulation of blood flow in microvessels and numerical experiments on a cell-free layer. [Internet] [Masters thesis]. University of Texas – Austin; 2007. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/16258.

Council of Science Editors:

Jee, Sol Keun 1. Computer simulation of blood flow in microvessels and numerical experiments on a cell-free layer. [Masters Thesis]. University of Texas – Austin; 2007. Available from: http://hdl.handle.net/2152/16258

3. Chan, Jesse L. A DPG method for convection-diffusion problems.

Degree: PhD, Computational and Applied Mathematics, 2013, University of Texas – Austin

URL: http://hdl.handle.net/2152/21417

► Over the last three decades, CFD simulations have become commonplace as a tool in the engineering and design of high-speed aircraft. Experiments are often complemented… (more)

▼ Over the last three decades, CFD simulations have become commonplace as a tool in the engineering and design of high-speed aircraft. Experiments are often complemented by computational simulations, and CFD technologies have proved very useful in both the reduction of aircraft development cycles, and in the simulation of conditions difficult to reproduce experimentally. Great advances have been made in the field since its introduction, especially in areas of meshing, computer architecture, and solution strategies. Despite this, there still exist many computational limitations in existing CFD methods; in particular, reliable higher order and hp-adaptive methods for the Navier-Stokes equations that govern viscous compressible flow. Solutions to the equations of viscous flow can display shocks and boundary layers, which are characterized by localized regions of rapid change and high gradients. The use of adaptive meshes is crucial in such settings – good resolution for such problems under uniform meshes is computationally prohibitive and impractical for most physical regimes of interest. However, the construction of "good" meshes is a difficult task, usually requiring a-priori knowledge of the form of the solution. An alternative to such is the construction of automatically adaptive schemes; such methods begin with a coarse mesh and refine based on the minimization of error. However, this task is difficult, as the convergence of numerical methods for problems in CFD is notoriously sensitive to mesh quality. Additionally, the use of adaptivity becomes more difficult in the context of higher order and hp methods. Many of the above issues are tied to the notion of robustness, which we define loosely for CFD applications as the degradation of the quality of numerical solutions on a coarse mesh with respect to the Reynolds number, or nondimensional viscosity. For typical physical conditions of interest for the compressible Navier-Stokes equations, the Reynolds number dictates the scale of shock and boundary layer phenomena, and can be extremely high – on the order of 10⁷ in a unit domain. For an under-resolved mesh, the Galerkin finite element method develops large oscillations which prevent convergence and pollute the solution. The issue of robustness for finite element methods was addressed early on by Brooks and Hughes in the SUPG method, which introduced the idea of residual-based stabilization to combat such oscillations. Residual-based stabilizations can alternatively be viewed as modifying the standard finite element test space, and consequently the norm in which the finite element method converges. Demkowicz and Gopalakrishnan generalized this idea in 2009 by introducing the Discontinous Petrov-Galerkin (DPG) method with optimal test functions, where test functions are determined such that they minimize the discrete linear residual in a dual space. Under the ultra-weak variational formulation, these test functions can be computed locally to yield a symmetric, positive-definite system. The main… Advisors/Committee Members: Demkowicz, Leszek (advisor), Moser, Robert deLancey (advisor).

Subjects/Keywords: Finite element methods; Discontinuous Galerkin; Petrov-Galerkin; Optimal test functions; Minimum residual methods; Convection-diffusion; Compressible flow

10 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Chan, J. L. (2013). A DPG method for convection-diffusion problems. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/21417

Chicago Manual of Style (16^th Edition):

Chan, Jesse L. “A DPG method for convection-diffusion problems.” 2013. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/21417.

MLA Handbook (7^th Edition):

Chan, Jesse L. “A DPG method for convection-diffusion problems.” 2013. Web. 07 Mar 2021.

Vancouver:

Chan JL. A DPG method for convection-diffusion problems. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2013. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/21417.

Council of Science Editors:

Chan JL. A DPG method for convection-diffusion problems. [Doctoral Dissertation]. University of Texas – Austin; 2013. Available from: http://hdl.handle.net/2152/21417

4. Roberts, Nathan Vanderkooy. A discontinuous Petrov-Galerkin methodology for incompressible flow problems.

Degree: PhD, Computational and Applied Mathematics, 2013, University of Texas – Austin

URL: http://hdl.handle.net/2152/21174

► Incompressible flows – flows in which variations in the density of a fluid are negligible – arise in a wide variety of applications, from hydraulics… (more)

▼ Incompressible flows – flows in which variations in the density of a fluid are negligible – arise in a wide variety of applications, from hydraulics to aerodynamics. The incompressible Navier-Stokes equations which govern such flows are also of fundamental physical and mathematical interest. They are believed to hold the key to understanding turbulent phenomena; precise conditions for the existence and uniqueness of solutions remain unknown – and establishing such conditions is the subject of one of the Clay Mathematics Institute's Millennium Prize Problems. Typical solutions of incompressible flow problems involve both fine- and large-scale phenomena, so that a uniform finite element mesh of sufficient granularity will at best be wasteful of computational resources, and at worst be infeasible because of resource limitations. Thus adaptive mesh refinements are required. In industry, the adaptivity schemes used are ad hoc, requiring a domain expert to predict features of the solution. A badly chosen mesh may cause the code to take considerably longer to converge, or fail to converge altogether. Typically, the Navier-Stokes solve will be just one component in an optimization loop, which means that any failure requiring human intervention is costly. Therefore, I pursue technological foundations for a solver of the incompressible Navier-Stokes equations that provides robust adaptivity starting with a coarse mesh. By robust, I mean both that the solver always converges to a solution in predictable time, and that the adaptive scheme is independent of the problem – no special expertise is required for adaptivity. The cornerstone of my approach is the discontinuous Petrov-Galerkin (DPG) finite element methodology developed by Leszek Demkowicz and Jay Gopalakrishnan. For a large class of problems, DPG can be shown to converge at optimal rates. DPG also provides an accurate mechanism for measuring the error, and this can be used to drive adaptive mesh refinements. Several approximations to Navier-Stokes are of interest, and I study each of these in turn, culminating in the study of the steady 2D incompressible Navier-Stokes equations. The Stokes equations can be obtained by neglecting the convective term; these are accurate for "creeping" viscous flows. The Oseen equations replace the convective term, which is nonlinear, with a linear approximation. The steady-state incompressible Navier-Stokes equations approximate the transient equations by neglecting time variations. Crucial to this work is Camellia, a toolbox I developed for solving DPG problems which uses the Trilinos numerical libraries. Camellia supports 2D meshes of triangles and quads of variable polynomial order, allows simple specification of variational forms, supports h- and p-refinements, and distributes the computation of the stiffness matrix, among other features. The central contribution of this dissertation is design and development of mathematical techniques and software, based on the DPG method, for solving the 2D incompressible Navier-Stokes equations… Advisors/Committee Members: Demkowicz, Leszek (advisor), Moser, Robert deLancey (advisor).

Subjects/Keywords: Finite element methods; Discontinuous Galerkin methods; Petrov-Galerkin methods; Navier-Stokes equations; Fluid dynamics; Stokes equations; DPG

10 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Roberts, N. V. (2013). A discontinuous Petrov-Galerkin methodology for incompressible flow problems. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/21174

Chicago Manual of Style (16^th Edition):

Roberts, Nathan Vanderkooy. “A discontinuous Petrov-Galerkin methodology for incompressible flow problems.” 2013. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/21174.

MLA Handbook (7^th Edition):

Roberts, Nathan Vanderkooy. “A discontinuous Petrov-Galerkin methodology for incompressible flow problems.” 2013. Web. 07 Mar 2021.

Vancouver:

Roberts NV. A discontinuous Petrov-Galerkin methodology for incompressible flow problems. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2013. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/21174.

Council of Science Editors:

Roberts NV. A discontinuous Petrov-Galerkin methodology for incompressible flow problems. [Doctoral Dissertation]. University of Texas – Austin; 2013. Available from: http://hdl.handle.net/2152/21174

University of Texas – Austin

5. Yang, Shan. A shape Hessian-based analysis of roughness effects on fluid flows.

Degree: PhD, Computational and Applied Mathematics, 2011, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2011-08-4036

► The flow of fluids over solid surfaces is an integral part of many technologies, and the analysis of such flows is important to the design… (more)

▼ The flow of fluids over solid surfaces is an integral part of many technologies, and the analysis of such flows is important to the design and operation of these technologies. Solid surfaces, however, are generally rough at some scale, and analyzing the effects of such roughness on fluid flows represents a significant challenge. There are two fluid flow situations in which roughness is particularly important, because the fluid shear layers they create can be very thin, of order the height of the roughness. These are very high Reynolds number turbulent wall-bounded flows (the viscous wall layer is very thin), and very low Reynolds number lubrication flows (the lubrication layer between moving surfaces is very thin). Analysis in both of these flow domains has long accounted for roughness through empirical adjustments to the smooth-wall analysis, with empirical parameters describing the fluid dynamic roughness effects. The ability to determine these effects from a topographic description of the roughness is limited (lubrication) or non-existent (turbulence). The commonly used parameter, the equivalent sand grain roughness, can be determined in terms of the change in the rate of viscous energy dissipation caused by the roughness and is generally obtained by measuring the effects on a fluid flow. However, determining fluid dynamic effects from roughness characteristics is critical to effective engineering analysis. Characterization of this mapping from roughness topography to fluid dynamic impact is the main topic of the dissertation. Using the mathematical tools of shape calculus, we construct this mapping by defining the roughness functional and derive its first- and second- order shape derivatives, i.e., the derivatives of the roughness functional with respect to the roughness topography. The results of the shape gradient and complete spectrum of the shape Hessian are presented for the low Reynolds number lubrication flows. Flow predictions based on this derivative information is shown to be very accurate for small roughness. However, for the study of high Reynolds number turbulent flows, the direct extension of the current approach fails due to the chaotic nature of turbulent flows. Challenges and possible approaches are discussed for the turbulence problem as well as a model problem, the sensitivity analysis of the Lorenz system. Advisors/Committee Members: Ghattas, Omar N. (advisor), Moser, Robert deLancey (advisor), Arbogast, Todd (committee member), Goldstein, David (committee member), Ying, Lexing (committee member).

Subjects/Keywords: Roughness analysis; Shape calculus; Navier-Stokes flow

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Yang, S. (2011). A shape Hessian-based analysis of roughness effects on fluid flows. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2011-08-4036

Chicago Manual of Style (16^th Edition):

Yang, Shan. “A shape Hessian-based analysis of roughness effects on fluid flows.” 2011. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/ETD-UT-2011-08-4036.

MLA Handbook (7^th Edition):

Yang, Shan. “A shape Hessian-based analysis of roughness effects on fluid flows.” 2011. Web. 07 Mar 2021.

Vancouver:

Yang S. A shape Hessian-based analysis of roughness effects on fluid flows. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2011. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/ETD-UT-2011-08-4036.

Council of Science Editors:

Yang S. A shape Hessian-based analysis of roughness effects on fluid flows. [Doctoral Dissertation]. University of Texas – Austin; 2011. Available from: http://hdl.handle.net/2152/ETD-UT-2011-08-4036

University of Texas – Austin

6. -2456-1577. Anisotropic hybrid turbulence modeling with specific application to the simulation of pulse-actuated dynamic stall control.

Degree: PhD, Mechanical engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/33393

► Experimental studies have shown pulse actuated dynamic stall control may provide a simple means to significantly increase the performance of lifting surfaces and expand their… (more)

Subjects/Keywords: Turbulence; RANS; LES; Hybrid; V2f; Simulation; Anisotropic; Inhomogeneous; Resolution; SGS; Structure-function; Stall control

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

-2456-1577. (2015). Anisotropic hybrid turbulence modeling with specific application to the simulation of pulse-actuated dynamic stall control. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/33393

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-2456-1577. “Anisotropic hybrid turbulence modeling with specific application to the simulation of pulse-actuated dynamic stall control.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/33393.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-2456-1577. “Anisotropic hybrid turbulence modeling with specific application to the simulation of pulse-actuated dynamic stall control.” 2015. Web. 07 Mar 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-2456-1577. Anisotropic hybrid turbulence modeling with specific application to the simulation of pulse-actuated dynamic stall control. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/33393.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-2456-1577. Anisotropic hybrid turbulence modeling with specific application to the simulation of pulse-actuated dynamic stall control. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/33393

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

7. Zhou, Jun, Ph. D. Modeling and simulation of thermal ablation in vascularized tissues.

Degree: PhD, Mechanical engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/31552

► Thermal ablation, which uses localized heating by external energy sour-ces to destroy abnormal tissues, has been increasingly used as a treatment modality for cancers. Its… (more)

▼ Thermal ablation, which uses localized heating by external energy sour-ces to destroy abnormal tissues, has been increasingly used as a treatment modality for cancers. Its efficacy hinges on the ability to control temperature and induce sufficient thermal damage in the targeted tissue regions. However, it is difficult for clinicians to decide what treatment settings should be applied to obtain the best treatment outcome while minimizing adverse effects. Help from numerical simulations in the treatment planning process would therefore be highly valuable, if the predictions are realistic, reliable and accurate. The complexity of tissue structures and the coupling of heat transfer with other biophysical phenomena such as blood perfusion, tissue damage and thermoregulation make it a challenge to predict temperature fields and thermal damage in living tissues. Approximate models with uncertain parameters are then used in the simulations. The important question is, which features are necessary to include in a model for plausible predictions to guide clinical treatment? Furthermore, what can be done to improve prediction accuracy? To address these issues a series of numerical simulations of radiofrequency (RF) ablation were performed that include the following effects: 1) the thermal effects of micro vascular perfusion, 2) the impact of tissue damage on that perfusion, and 3) the thermal effects of discrete blood vessels. In addition two distinct models of the thermal effects of perfusion, with very different underlying assumptions were used: Penne's bioheat transfer model, and a porous media model. The former is expected to be valid at large scales (e.g.,~the scale of a whole organ), while the latter is expected to be valid at small scales (e.g.,~the scale of a capillary bed). It is not clear what perfusion model is most appropriate at the intermediate scale of thermal ablation. The results of these simulations were analyzed to identify the most important factors to consider in treatment planning for RF ablation. By far the most important uncertainty in predicting the tissue damaged by RF ablation therapy was due to the difference between the two ablation models studied, resulting in a factor of two difference in the predicted volume of damaged tissue. Also important were the effective porosity of the tissue and the perfusion rate, especially in the case of the Pennes' perfusion model, and the presence of blood vessels larger than 0.5 mm in diameter and closer than 20 mm from the applicator. Of particular interest is the finding that it is very difficult to damage all tissue very close to a blood vessel larger than 3 mm in diameter, because of the cooling it provides. These observations suggest improved perfusion modeling, reliable determination of effective porosity and perfusion rate, and the mapping of large vessels in the treatment area would all improve the ability to predict the response to RF thermal ablation for treatment planning. Advisors/Committee Members: Moser, Robert deLancey (advisor), Feng, Yusheng (advisor), Biros, George (committee member), Diller, Kenneth R (committee member), Li, Wei (committee member).

Subjects/Keywords: Thermal ablation; Vascularized tissue; Modeling; Simulation

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Zhou, Jun, P. D. (2015). Modeling and simulation of thermal ablation in vascularized tissues. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/31552

Chicago Manual of Style (16^th Edition):

Zhou, Jun, Ph D. “Modeling and simulation of thermal ablation in vascularized tissues.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/31552.

MLA Handbook (7^th Edition):

Zhou, Jun, Ph D. “Modeling and simulation of thermal ablation in vascularized tissues.” 2015. Web. 07 Mar 2021.

Vancouver:

Zhou, Jun PD. Modeling and simulation of thermal ablation in vascularized tissues. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/31552.

Council of Science Editors:

Zhou, Jun PD. Modeling and simulation of thermal ablation in vascularized tissues. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/31552

8. Malaya, Nicholas Penha. Numerical simulation of synthetic, buoyancy-induced columnar vortices.

Degree: PhD, Mechanical engineering, 2016, University of Texas – Austin

URL: http://hdl.handle.net/2152/45689

► Much of the solar energy incident on the Earth’s surface is absorbed into the ground, which in turn heats the air layer above the surface.… (more)

Subjects/Keywords: CFD; Scientific computing; Optimization; Dust devils

12 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Malaya, N. P. (2016). Numerical simulation of synthetic, buoyancy-induced columnar vortices. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/45689

Chicago Manual of Style (16^th Edition):

Malaya, Nicholas Penha. “Numerical simulation of synthetic, buoyancy-induced columnar vortices.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/45689.

MLA Handbook (7^th Edition):

Malaya, Nicholas Penha. “Numerical simulation of synthetic, buoyancy-induced columnar vortices.” 2016. Web. 07 Mar 2021.

Vancouver:

Malaya NP. Numerical simulation of synthetic, buoyancy-induced columnar vortices. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/45689.

Council of Science Editors:

Malaya NP. Numerical simulation of synthetic, buoyancy-induced columnar vortices. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/45689

University of Texas – Austin

9. Morrison, Rebecca Elizabeth. On the representation of model inadequacy : a stochastic operator approach.

Degree: PhD, Computational science, engineering, and mathematics, 2016, University of Texas – Austin

URL: http://hdl.handle.net/2152/40259

► Mathematical models of physical systems are subject to many sources of uncertainty such as measurement errors and uncertain initial and boundary conditions. After accounting for… (more)

▼ Mathematical models of physical systems are subject to many sources of uncertainty such as measurement errors and uncertain initial and boundary conditions. After accounting for these uncertainties, it is often revealed that there remains some discrepancy between the model output and the observations; if so, the model is said to be inadequate. In practice, the inadequate model may be the best that is available or tractable, and so despite its inadequacy the model may be used to make predictions of unobserved quantities. In this case, a representation of the inadequacy is necessary, so the impact of the observed discrepancy can be determined. We investigate this problem in the context of chemical kinetics and propose a new technique to account for model inadequacy that is both probabilistic and physically meaningful. Chemical reactions are generally modeled by a set of nonlinear ordinary differential equations (ODEs) for the concentrations of the species and temperature. In this work, a stochastic inadequacy operator S is introduced which includes three parts. The first is represented by a random matrix which is embedded within the ODEs of the concentrations. The matrix is required to satisfy several physical constraints, and its most general form exhibits some useful properties, such as having only non-positive eigenvalues. The second is a smaller but specific set of nonlinear terms that also modifies the species’ concentrations, and the third is an operator that properly accounts for changes to the energy equation due to the previous changes. The entries of S are governed by probability distributions, which in turn are characterized by a set of hyperparameters. The model parameters and hyperparameters are calibrated using high-dimensional hierarchical Bayesian inference, with data from a range of initial conditions. This allows the use of the inadequacy operator on a wide range of scenarios, rather than correcting any particular realization of the model with a corresponding data set. We apply the method to typical problems in chemical kinetics including the reaction mechanisms of hydrogen and methane combustion. We also study how the inadequacy representation affects an unobserved quantity of interest— the flamespeed of a one-dimensional hydrogen laminar flame. Advisors/Committee Members: Moser, Robert deLancey (advisor), Oden, John Tinsley (committee member), Ghattas, Omar (committee member), Henkelman, Graeme (committee member), Oliver, Todd A (committee member), Simmons, Christopher S (committee member).

Subjects/Keywords: Uncertainty quantification; Model inadequacy; Stochastic operator; Bayesian inference; Chemical kinetics

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Morrison, R. E. (2016). On the representation of model inadequacy : a stochastic operator approach. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/40259

Chicago Manual of Style (16^th Edition):

Morrison, Rebecca Elizabeth. “On the representation of model inadequacy : a stochastic operator approach.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/40259.

MLA Handbook (7^th Edition):

Morrison, Rebecca Elizabeth. “On the representation of model inadequacy : a stochastic operator approach.” 2016. Web. 07 Mar 2021.

Vancouver:

Morrison RE. On the representation of model inadequacy : a stochastic operator approach. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/40259.

Council of Science Editors:

Morrison RE. On the representation of model inadequacy : a stochastic operator approach. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/40259

University of Texas – Austin

10. Nugen, Frederick Theodore. Advances in saccular aneurysm biomechanics : enlargement via rate-sensitive inelastic growth, bio-mathematical stages of aneurysm disease, and initiation profiles.

Degree: PhD, Mechanical engineering, 2016, University of Texas – Austin

URL: http://hdl.handle.net/2152/45553

► I have created the first simulation of saccular aneurysm initiation and development from a healthy artery geometry. It is capable of growing saccular aneurysm geometries… (more)

▼ I have created the first simulation of saccular aneurysm initiation and development from a healthy artery geometry. It is capable of growing saccular aneurysm geometries from patient-specific data. My model describes aneurysm behavior in a way that bridges fields. I assume arteries are made of a rate-sensitive inelastic material which produces irreversible deformation when it is overstressed. The material is assumed to consist of a 3D hyperelastic background material embedded with 1D transversely-isotropic fibers. I optionally use a Winkler foundation term to model support of external organs and distinguish healthy tissue from diseased tissue. Lesions are defined as a local degradation of artery wall structure. My work suggests passive mechanisms of growth are insufficient for predicting saccular aneurysms. Furthermore, I identify a new concept of stages of aneurysm disease. The stages connect mathematical descriptions of the simulation with clinically-relevant changes in the modeled aneurysm. They provide an evocative framework through which clinical descriptions of arteries can be neatly matched with mathematical features of the model. The framework gives a common language of concepts – e.g., collagen fiber, pseudoelastic limit, inelastic strain, and subclinical lesion – through which researchers in different fields, with different terminologies, can engage in an ongoing dialog: under the model, questions in medicine can be translated into equivalent questions in mathematics. A new stage of “subclinical lesion” has been identified, with a suggested direction for future biomechanics research into early detection and treatment of aneurysms. This stage defines a preclinical aneurysm-producing lesion which occurs before any artery dilatation. It is a stage of aneurysm development involving microstructural changes in artery wall makeup. Under the model, this stage can be identified by its reduced strength: its structural support is still within normal limits, but presumably would perform more poorly in ex vivo failure testing than healthy tissue from the same individual. I encourage clinicians and biomechanicians to measure elastin degradation, and to build detailed multiscale models of elastin degradation profiles as functions of aging and tortuosity; and similarly for basal tone. I hope such measurements will to lead to early detection and treatment of aneurysms. I give specific suggestions of biological tissue experiments to be performed for improving and reinforming constitutive modeling techniques. Advisors/Committee Members: Hughes, Thomas J. R. (advisor), Moser, Robert deLancey (advisor), Sacks, Michael S (committee member), Barr, Ronald (committee member), Gonzalez, Oscar (committee member), Kemper, Craig (committee member), Beasley, Haley K (committee member).

Subjects/Keywords: Saccular aneurysm initiation; Saccular aneurysm; Cranial aneurysm; Aneurysm; Arterial modeling; Inelasticity; Rate-sensitive hyperelasticity; Collagen fibers; Aneurysm stages; Isogeometric analysis; Numerical simulation; Cardiovascular engineering; Computational medicine

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Nugen, F. T. (2016). Advances in saccular aneurysm biomechanics : enlargement via rate-sensitive inelastic growth, bio-mathematical stages of aneurysm disease, and initiation profiles. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/45553

Chicago Manual of Style (16^th Edition):

Nugen, Frederick Theodore. “Advances in saccular aneurysm biomechanics : enlargement via rate-sensitive inelastic growth, bio-mathematical stages of aneurysm disease, and initiation profiles.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/45553.

MLA Handbook (7^th Edition):

Nugen, Frederick Theodore. “Advances in saccular aneurysm biomechanics : enlargement via rate-sensitive inelastic growth, bio-mathematical stages of aneurysm disease, and initiation profiles.” 2016. Web. 07 Mar 2021.

Vancouver:

Nugen FT. Advances in saccular aneurysm biomechanics : enlargement via rate-sensitive inelastic growth, bio-mathematical stages of aneurysm disease, and initiation profiles. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/45553.

Council of Science Editors:

Nugen FT. Advances in saccular aneurysm biomechanics : enlargement via rate-sensitive inelastic growth, bio-mathematical stages of aneurysm disease, and initiation profiles. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/45553

University of Texas – Austin

11. -6380-0852. Representing model-form uncertainty from missing microstructural information.

Degree: PhD, Computational Science, Engineering, and Mathematics, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/10112

► A common challenge in modeling multiscale phenomena lies in representing the dependence of macroscopic quantities on microscale dynamics. Incomplete information or limitations in computational resources… (more)

▼ A common challenge in modeling multiscale phenomena lies in representing the dependence of macroscopic quantities on microscale dynamics. Incomplete information or limitations in computational resources make it impossible to resolve the microscale dynamics and their effect on those at the macroscale. To obtain a model of the phenomenon that can be used to make predictions, approximations must be made. For instance, it is commonly assumed that microscale effects on the macroscale can be represented with macroscopic quantities, effectively removing any dependence on the microstate. Such approximations introduce uncertainty in the model. When the approximations are invalid, the uncertainty is significant and must be quantified to assess the reliability of the model. This work focuses on the formulation of a model-form uncertainty representation to account for such missing dependencies. The process by which a model-form uncertainty representation is formulated is an open area of research, so particular attention is paid to determining the feasibility and inherent challenges of its development. The representation is developed in the context of a simplified testbed problem, accounting for uncertainty in a model of mean contaminant transport through a heterogeneous porous medium. In heterogeneous media, the evolution of the mean depends on small-scale fluctuations of the flow velocity from its mean and their induced fluctuations on the detailed concentration field. However, these fluctuations can neither be observed nor resolved. In this work, model-form uncertainty caused by the unresolved dependence on the small-scale fluctuations is represented as an infinite-dimensional stochastic operator acting on the mean concentration. Physical constraints are enforced through its eigendecomposition, and uncertainty is encoded in its eigenvalues by casting them as random variables. The feasibility of inferring their mean values using observations of the mean concentration is explored, and a novel method of extracting samples from their distribution using direct numerical simulation is discussed. These findings are used to develop a stochastic model for the probability distribution of the operator's eigenvalues, and its validity is assessed using forward propagation of uncertainty to the mean concentration. Advisors/Committee Members: Moser, Robert deLancey (advisor), Dawson, Clint (committee member), Ghattas, Omar (committee member), Mueller, Peter (committee member), McDougall, Damon (committee member), Oliver, Todd A (committee member).

Subjects/Keywords: Uncertainty quantification; Model inadequacy

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

-6380-0852. (2019). Representing model-form uncertainty from missing microstructural information. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/10112

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-6380-0852. “Representing model-form uncertainty from missing microstructural information.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://dx.doi.org/10.26153/tsw/10112.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-6380-0852. “Representing model-form uncertainty from missing microstructural information.” 2019. Web. 07 Mar 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-6380-0852. Representing model-form uncertainty from missing microstructural information. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Mar 07]. Available from: http://dx.doi.org/10.26153/tsw/10112.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-6380-0852. Representing model-form uncertainty from missing microstructural information. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/10112

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

12. Lopez Mejia, Omar Dario. Computational study of a NACA4415 airfoil using synthetic jet control.

Degree: PhD, Mechanical Engineering, 2009, University of Texas – Austin

URL: http://hdl.handle.net/2152/10683

► Synthetic jet actuators for flow control applications have been an active topic of experimental research since the 90’s. Numerical simulations have become an important complement… (more)

▼ Synthetic jet actuators for flow control applications have been an active topic of experimental research since the 90’s. Numerical simulations have become an important complement of that experimental work, providing detailed information of the dynamics of the controlled flow. This study is part of the AVOCET (Adaptive VOrticity Control Enabled flighT) project and is intended to provide computational support for the design and evaluation of closed-loop flow control with synthetic jet actuators for small scale Unmanned Aerial Vehicles (UAVs). The main objective is to analyze active flow control of a NACA4415 airfoil with tangential synthetic jets via computational modeling. A hybrid Reynolds-Averaged Navier-Stokes/Large Eddy Simulation (RANS/LES) turbulent model (called Delayed Detached-Eddy Simulation-DDES) was implemented in CDP, a kinetic energy conserving Computational Fluid Dynamics (CFD) code. CDP is a parallel unstructured grid incompressible flow solver, developed at the Center for Integrated Turbulence Simulations (CITS) at Stanford University. Two models of synthetic jet actuators have been developed and validated. The first is a detailed model in which the flow in and out of the actuator cavity is modeled. A second less costly model (RSSJ) was also developed in which the Reynolds stress produced by the actuator is modeled, based on information from the detailed model. Several static validation test cases at different angle of attack with modified NACA 4415 and Dragon Eye airfoils were performed. Numerical results show the effects of the actuators on the vortical structure of the flow, as well as on the aerodynamic properties. The main effect of the actuation on the time averaged vorticity field is a bending of the separation shear layer from the actuator toward the airfoil surface, resulting in changes in the aerodynamic properties. Full actuation of the suction side actuator reduces the pitching moment and increases the lift force, while the pressure side actuator increases the pitching moment and reduces the lift force. These observations are in agreement with experimental results. The effectiveness of the actuator is measured by the change in the aerodynamic properties of the airfoil in particular the lift ([Delta]C[subscript t]) and moment ([Delta]C[subscript m]) coefficients. Computational results for the actuator effectiveness show very good agreement with the experimental values (over the range of −2° to 10°). While the actuation modifies the global pressure distribution, the most pronounced effects are near the trailing edge in which a spike in the pressure coefficient (C[subscript p]) is observed. The local reduction of C[subscript p], for both the suction side and pressure side actuators, at x/c = 0.96 (the position of the actuators) is about 0.9 with respect to the unactuated case. This local reduction of the pressure is associated with the trapped vorticity and flow acceleration close to the trailing edge. The RSSJ model is designed to capture the synthetic jet time averaged behavior so that… Advisors/Committee Members: Moser, Robert deLancey (advisor).

Subjects/Keywords: Adaptive Vorticity Control Enabled Flight; Closed-loop flow control; Synthetic jet actuators; Unmanned Aerial Vehicles

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Lopez Mejia, O. D. (2009). Computational study of a NACA4415 airfoil using synthetic jet control. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/10683

Chicago Manual of Style (16^th Edition):

Lopez Mejia, Omar Dario. “Computational study of a NACA4415 airfoil using synthetic jet control.” 2009. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/10683.

MLA Handbook (7^th Edition):

Lopez Mejia, Omar Dario. “Computational study of a NACA4415 airfoil using synthetic jet control.” 2009. Web. 07 Mar 2021.

Vancouver:

Lopez Mejia OD. Computational study of a NACA4415 airfoil using synthetic jet control. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2009. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/10683.

Council of Science Editors:

Lopez Mejia OD. Computational study of a NACA4415 airfoil using synthetic jet control. [Doctoral Dissertation]. University of Texas – Austin; 2009. Available from: http://hdl.handle.net/2152/10683

13. Chang, Henry, 1976-. Modeling turbulence using optimal large eddy simulation.

Degree: PhD, Computational and Applied Mathematics, 2012, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2012-05-4988

► Most flows in nature and engineering are turbulent, and many are wall-bounded. Further, in turbulent flows, the turbulence generally has a large impact on the… (more)

▼ Most flows in nature and engineering are turbulent, and many are wall-bounded. Further, in turbulent flows, the turbulence generally has a large impact on the behavior of the flow. It is therefore important to be able to predict the effects of turbulence in such flows. The Navier-Stokes equations are known to be an excellent model of the turbulence phenomenon. In simple geometries and low Reynolds numbers, very accurate numerical solutions of the Navier-Stokes equations (direct numerical simulation, or DNS) have been used to study the details of turbulent flows. However, DNS of high Reynolds number turbulent flows in complex geometries is impractical because of the escalation of computational cost with Reynolds number, due to the increasing range of spatial and temporal scales. In Large Eddy Simulation (LES), only the large-scale turbulence is simulated, while the effects of the small scales are modeled (subgrid models). LES therefore reduces computational expense, allowing flows of higher Reynolds number and more complexity to be simulated. However, this is at the cost of the subgrid modeling problem. The goal of the current research is then to develop new subgrid models consistent with the statistical properties of turbulence. The modeling approach pursued here is that of "Optimal LES". Optimal LES is a framework for constructing models with minimum error relative to an ideal LES model. The multi-point statistics used as input to the optimal LES procedure can be gathered from DNS of the same flow. However, for an optimal LES to be truly predictive, we must free ourselves from dependence on existing DNS data. We have done this by obtaining the required statistics from theoretical models which we have developed. We derived a theoretical model for the three-point third-order velocity correlation for homogeneous, isotropic turbulence in the inertial range. This model is shown be a good representation of DNS data, and it is used to construct optimal quadratic subgrid models for LES of forced isotropic turbulence with results which agree well with theory and DNS. The model can also be filtered to determine the filtered two-point third-order correlation, which describes energy transfer among filtered (large) scales in LES. LES of wall-bounded flows with unresolved wall layers commonly exhibit good prediction of mean velocities and significant over-prediction of streamwise component energies in the near-wall region. We developed improved models for the nonlinear term in the filtered Navier-Stokes equation which result in better predicted streamwise component energies. These models involve (1) Reynolds decomposition of the nonlinear term and (2) evaluation of the pressure term, which removes the divergent part of the nonlinear models. These considerations significantly improved the performance of our optimal models, and we expect them to apply to other subgrid models as well. Advisors/Committee Members: Moser, Robert deLancey (advisor), Engquist, Bjorn (committee member), Ghattas, Omar (committee member), Hughes, Thomas J. (committee member), Raman, Venkat (committee member).

Subjects/Keywords: Turbulence simulation; Large eddy simulation; Optimal large eddy simulation; Turbulence modeling; Subgrid models; Wall-bounded turbulence; Channel flow; Three-point third-order velocity correlation; Triple velocity correlation

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Chang, Henry, 1. (2012). Modeling turbulence using optimal large eddy simulation. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2012-05-4988

Chicago Manual of Style (16^th Edition):

Chang, Henry, 1976-. “Modeling turbulence using optimal large eddy simulation.” 2012. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/ETD-UT-2012-05-4988.

MLA Handbook (7^th Edition):

Chang, Henry, 1976-. “Modeling turbulence using optimal large eddy simulation.” 2012. Web. 07 Mar 2021.

Vancouver:

Chang, Henry 1. Modeling turbulence using optimal large eddy simulation. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2012. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/ETD-UT-2012-05-4988.

Council of Science Editors:

Chang, Henry 1. Modeling turbulence using optimal large eddy simulation. [Doctoral Dissertation]. University of Texas – Austin; 2012. Available from: http://hdl.handle.net/2152/ETD-UT-2012-05-4988

14. Wright, Eric Thomas. Bayesian learning methods for potential energy parameter inference in coarse-grained models of atomistic systems.

Degree: PhD, Computational and Applied Mathematics, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/30464

► The present work addresses issues related to the derivation of reduced models of atomistic systems, their statistical calibration, and their relation to atomistic models of… (more)

Subjects/Keywords: Coarse-grained modeling; Uncertainty quantification; Bayesian statistics; Theoretical chemistry; Organic photovoltaic materials

10 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Wright, E. T. (2015). Bayesian learning methods for potential energy parameter inference in coarse-grained models of atomistic systems. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/30464

Chicago Manual of Style (16^th Edition):

Wright, Eric Thomas. “Bayesian learning methods for potential energy parameter inference in coarse-grained models of atomistic systems.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/30464.

MLA Handbook (7^th Edition):

Wright, Eric Thomas. “Bayesian learning methods for potential energy parameter inference in coarse-grained models of atomistic systems.” 2015. Web. 07 Mar 2021.

Vancouver:

Wright ET. Bayesian learning methods for potential energy parameter inference in coarse-grained models of atomistic systems. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/30464.

Council of Science Editors:

Wright ET. Bayesian learning methods for potential energy parameter inference in coarse-grained models of atomistic systems. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/30464

15. Lee, Myoungkyu. Direct numerical simulation (DNS) for incompressible turbulent channel flow at Reτ = 5200.

Degree: PhD, Mechanical engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/33514

► Nearly all moving objects on Earth pass through fluids and many of them move at high speed. This makes high Re wall-bounded turbulent flows of… (more)

▼ Nearly all moving objects on Earth pass through fluids and many of them move at high speed. This makes high Re wall-bounded turbulent flows of great technological impor- tance. To study high Re wall-bounded turbulence, high spatial and temporal resolution is required due to the multi-scale nature of turbulence. Direct numerical simulation (DNS) is a technique for the study of turbulence in which the Navier-Stoke equations, the governing equations of fluid flow, are solved with sufficient resolution to represent all the scales of tur- bulence. Hence, DNS is very expensive and always limited by computational capability. To perform DNS on the most advanced high performance computing systems, extensive code optimization is required. A new turbulence DNS code, PoongBack, was developed for the studies reported here. It shows excellent performance and scalability (∼97%) on upto 786k cores on Mira at Argonne Leadership Computing Facility. We have performed DNS of turbulent channel flow using a Fourier-Galerkin method in the streamwise(x) and spanwise (z) directions and a B-Splines collocation method in the wall-normal (y) direction. The highest Reynolds number based on shear velocity (uτ = √(τw/ρ)), Reτ is approximately 5200. The simulation results exhibit a number of the char- acteristics of high Re wall-bounded turbulent flows. For example, a region where the mean velocity has a logarithmic variation is observed, with von Kármán constant κ = 0.384±0.004. There is also a logarithmic dependence of the variance of the spanwise velocity component, though not the streamwise component. A distinct separation of scales exists between the large outer-layer structures and small inner-layer structures. At intermediate distances from the wall, the one-dimensional spectrum of the streamwise velocity fluctuation in both the streamwise and spanwise directions exhibits 1/k dependence over a short range in wavenum- ber (k). Further, consistent with previous experimental observations, when these spectra are multiplied by k (premultiplied spectra), they have a bimodal structure with local peaks located at wavenumbers on either side of the 1/k range. To study the scale dependence of the dynamics of the Reynolds stress components, we applied a spectral analysis to the terms in the Reynolds stress transport equation (RSTE). It is shown that only the turbulent transport terms show significant Re dependencies. Further- more, the turbulent transport terms can be decomposed into two parts, one that contributes to transport in the wall-normal direction and one that is responsible for transfer between length scales. The results show that the large scale motion in the outer region has direct effects on the flow in the near-wall region through transport of turbulent kinetic energy. Also, a reverse energy cascade from intermediate scales to large scales is observed in the spanwise velocity fluctuations. Advisors/Committee Members: Moser, Robert deLancey (advisor), Biros, George (committee member), Bogard, David G. (committee member), Murthy, Jayathi (committee member), Oliver, Todd A. (committee member).

Subjects/Keywords: Turbulence; Wall-bounded turbulent flow; Direct numerical simulation; 3D-FFT; Supercomputing; Computational fluid dynamics

12 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Lee, M. (2015). Direct numerical simulation (DNS) for incompressible turbulent channel flow at Reτ = 5200. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/33514

Chicago Manual of Style (16^th Edition):

Lee, Myoungkyu. “Direct numerical simulation (DNS) for incompressible turbulent channel flow at Reτ = 5200.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/33514.

MLA Handbook (7^th Edition):

Lee, Myoungkyu. “Direct numerical simulation (DNS) for incompressible turbulent channel flow at Reτ = 5200.” 2015. Web. 07 Mar 2021.

Vancouver:

Lee M. Direct numerical simulation (DNS) for incompressible turbulent channel flow at Reτ = 5200. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/33514.

Council of Science Editors:

Lee M. Direct numerical simulation (DNS) for incompressible turbulent channel flow at Reτ = 5200. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/33514

16. Sung, Yonduck. Large eddy simulation of TiO₂ nanoparticle evolution in turbulent flames.

Degree: PhD, Mechanical Engineering, 2011, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2011-12-4465

► Flame based synthesis is a major manufacturing process of commercially valuable nanoparticles for large-scale production. However, this important industrial process has been advanced mostly by… (more)

▼ Flame based synthesis is a major manufacturing process of commercially valuable nanoparticles for large-scale production. However, this important industrial process has been advanced mostly by trial-and-error based evolutionary studies owing to the fact that it involves tightly coupled multiphysics flow phenomena. For large scale synthesis of nanoparticles, different physical and chemical processes exist, including turbulence, fuel combustion, precursor oxidation, and nanoparticle dynamics exist. A reliable and predictive computational model based on fundamental physics and chemistry can provide tremendous insight. Development of such comprehensive computational models faces challenges as they must provide accurate descriptions not only of the individual physical processes but also of the strongly coupled, nonlinear interactions among them. In this work, a multiscale computational model for flame synthesis of TiO2 nanoparticles in a turbulent flame reactor is presented. The model is based on the large-eddy simulation (LES) methodology and incorporates detailed gas phase combustion and precursor oxidation chemistry as well as a comprehensive nanoparticle evolution model. A flamelet-based model is used to model turbulence-chemistry interactions. In particular, the transformation of TiCl4 to the solid primary nucleating TiO2 nanoparticles is represented us- ing an unsteady kinetic model considering 30 species and 70 reactions in order to accurately describe the critical nanoparticle nucleation process. The evolution of the TiO2 number density function is tracked using the quadrature method of moments (QMOM) for univariate particle number density function and conditional quadrature method of moments (CQMOM) for bivariate density distribution function. For validation purposes, the detailed computational model is compared against experimental data obtained from a canonical flame- based titania synthesis configuration, and reasonable agreement is obtained. Advisors/Committee Members: Moser, Robert deLancey (advisor), Raman, Venkat (advisor), Ezekoye, Ofodike A. (committee member), Matthews, Ronald D. (committee member), Clemens, Noel T. (committee member).

Subjects/Keywords: Large eddy simulation; TiO2 nanoparticle; Detailed TiCl4 oxidation chemistry; Quadrature method of moments; Moment correction

10 more images…

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Sung, Y. (2011). Large eddy simulation of TiO₂ nanoparticle evolution in turbulent flames. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2011-12-4465

Chicago Manual of Style (16^th Edition):

Sung, Yonduck. “Large eddy simulation of TiO₂ nanoparticle evolution in turbulent flames.” 2011. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/ETD-UT-2011-12-4465.

MLA Handbook (7^th Edition):

Sung, Yonduck. “Large eddy simulation of TiO₂ nanoparticle evolution in turbulent flames.” 2011. Web. 07 Mar 2021.

Vancouver:

Sung Y. Large eddy simulation of TiO₂ nanoparticle evolution in turbulent flames. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2011. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/ETD-UT-2011-12-4465.

Council of Science Editors:

Sung Y. Large eddy simulation of TiO₂ nanoparticle evolution in turbulent flames. [Doctoral Dissertation]. University of Texas – Austin; 2011. Available from: http://hdl.handle.net/2152/ETD-UT-2011-12-4465

University of Texas – Austin

17. Hira, Jeremy. Generalization of optimal finite-volume LES operators to anisotropic grids and variable stencils.

Degree: MSin Engineering, Mechanical Engineering, 2010, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2010-08-1948

► Optimal large eddy simulation (OLES) is an approach to LES sub-grid modeling that requires multi-point correlation data as input. Until now, this has been obtained… (more)

Subjects/Keywords: Turbulent flows; Optimal large-eddy simulation; Finite-volume operators

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Hira, J. (2010). Generalization of optimal finite-volume LES operators to anisotropic grids and variable stencils. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2010-08-1948

Chicago Manual of Style (16^th Edition):

Hira, Jeremy. “Generalization of optimal finite-volume LES operators to anisotropic grids and variable stencils.” 2010. Masters Thesis, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/ETD-UT-2010-08-1948.

MLA Handbook (7^th Edition):

Hira, Jeremy. “Generalization of optimal finite-volume LES operators to anisotropic grids and variable stencils.” 2010. Web. 07 Mar 2021.

Vancouver:

Hira J. Generalization of optimal finite-volume LES operators to anisotropic grids and variable stencils. [Internet] [Masters thesis]. University of Texas – Austin; 2010. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/ETD-UT-2010-08-1948.

Council of Science Editors:

Hira J. Generalization of optimal finite-volume LES operators to anisotropic grids and variable stencils. [Masters Thesis]. University of Texas – Austin; 2010. Available from: http://hdl.handle.net/2152/ETD-UT-2010-08-1948

University of Texas – Austin

18. Lee, Sei Young. Size and shape effects for the nano/micro particle dynamics in the microcirculation.

Degree: PhD, Mechanical Engineering, 2010, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2010-08-1672

► The nano/micro particles have been widely used as a carrier of therapeutic and contrast imaging agents. The nano/micro particles have many advantages, such as, specificity,… (more)

▼ The nano/micro particles have been widely used as a carrier of therapeutic and contrast imaging agents. The nano/micro particles have many advantages, such as, specificity, controlled release, multifunctionality and engineerability. By tuning the chemical, physical and geometrical properties, the efficacy of delivery of nano/micro particle can be improved. In this study, by analyzing the effect of physical and geometrical properties of particle, such as, size, shape, material property and flow condition, the optimal condition for particle delivery will be explored. The objectives of this study are (1) to develop predictive mathematical models and (2) experimental models for particle margination and adhesion, and (3) to find optimal particle geometry in terms of size and shape to enhance the efficiency of its delivery. The effect of particle size expressed in terms of Stokes number and shape, namely, spherical, ellipsoidal, hemispherical, discoidal and cylindrical particle on the particle trajectory is investigated. For discoidal and cylindrical particles, the effect of aspect ratio is also considered. To calculate particle trajectory in the linear shear flow near the substrate, Newton's law of motion is decomposed into hydrodynamic drag and resistance induced by particle motion. The drag and resistance is estimated through finite volume formulation using Fluent v6.3. Particle behavior in the linear shear flow does strongly depend on Stokes number. Spherical particle is transported following the streamline in the absence of external body force. However, non-spherical particles could across the streamline and marginate to the substrate. For non-spherical particles, the optimal [Stokes number] in terms of particle margination is observed; [Stokes number almost equal to] 20 for ellipsoidal, hemispherical and discoidal particle; [Stokes number almost equal to] 10 for cylindrical particle. For discoidal particle with [gamma subscript d]=0.2 shows fastest margination to the substrate. The effect of gravitational force is also considered with respect to the fluid direction. When the gravitational force is applied, mostly, gravitational force plays a dominant role for particle margination. However, using small particle aspect ratio ([gamma subscript d]=0.2 and 0.33), spontaneous drift induced by particle-fluid-substrate interaction could overcome gravitational effect in some cases ([Stokes number]=10, G=0.1). In addition the adhesion characteristic of spherical particle has been studied using in vitro micro fluidic chamber system with different particle size and flow condition. The experimental results are compared to the mathematical model developed by Decuzzi and Ferrari (Decuzzi and Ferrari, 2006) and in vivo test (Decuzzi et al., 2010). The optimal particle size for S=75 and 90 is found to be 4-5 [micrometer] through the in vitro non-specific interaction of spherical particle on the biological substrate. The suggested mathematical model has proven to be valid for current experimental condition. At the end, the… Advisors/Committee Members: Moser, Robert deLancey (advisor), Ferrari, Mauro, 1959- (advisor), Decuzzi, Paolo (committee member), Chen, Shaochen (committee member), Hidrovo, Carlos (committee member).

Subjects/Keywords: Particle dynamics; Linear shear flow; Adhesion; Accumulation; Vascular targeting; Drug delivery; Particle delivery; Mathematical models

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Lee, S. Y. (2010). Size and shape effects for the nano/micro particle dynamics in the microcirculation. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2010-08-1672

Chicago Manual of Style (16^th Edition):

Lee, Sei Young. “Size and shape effects for the nano/micro particle dynamics in the microcirculation.” 2010. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/ETD-UT-2010-08-1672.

MLA Handbook (7^th Edition):

Lee, Sei Young. “Size and shape effects for the nano/micro particle dynamics in the microcirculation.” 2010. Web. 07 Mar 2021.

Vancouver:

Lee SY. Size and shape effects for the nano/micro particle dynamics in the microcirculation. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2010. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/ETD-UT-2010-08-1672.

Council of Science Editors:

Lee SY. Size and shape effects for the nano/micro particle dynamics in the microcirculation. [Doctoral Dissertation]. University of Texas – Austin; 2010. Available from: http://hdl.handle.net/2152/ETD-UT-2010-08-1672

University of Texas – Austin

19. Jee, Sol Keun, 1979-. Flow control simulation with synthetic and pulsed jet actuator.

Degree: PhD, Mechanical Engineering, 2010, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2010-08-1676

► Two active flow control methods are investigated numerically to understand the mechanism by which they control aerodynamics in the presence of severe flow separation on… (more)

▼ Two active flow control methods are investigated numerically to understand the mechanism by which they control aerodynamics in the presence of severe flow separation on an airfoil. In particular, synthetic jets are applied to separated flows generated by additional surface feature (the actuators) near the trailing edge to obtain Coanda-like effects, and an impulse jet is used to control a stalled flow over an airfoil. A moving-grid scheme is developed, verified and validated to support simulations of external flow over moving bodies. Turbulent flow is modeled using detached eddy simulation (DES) turbulence models in the CFD code CDP (34) developed by Lopez (54). Synthetic jet actuation enhances turbulent mixing in flow separation regions, reduces the size of the separation, deflects stream lines closer to the surface and changes pressure distributions on the surface, all of which lead to bi-directional changes in the aerodynamic lift and moment. The external flow responds to actuation within about one convective time, which is significantly faster than for conventional control surfaces. Simulation of pitching airfoils shows that high-frequency synthetic jet affects the flow independently of the baseline frequencies associated with vortex shedding and airfoil dynamics. These unique features of synthetic jets are studied on a dynamically maneuvering airfoil with a closed-loop control system, which represents the response of the airfoil in wind-tunnel experiments and examines the controller for a rapidly maneuvering free-flight airfoil. An impulse jet, which is applied upstream of a nominal flow separation point, generates vortices that convect downstream, interact with the separating shear layer, dismantle the layer and allow following vortices to propagate along the surface in the separation region. These following vortices delay the separation point reattaching the boundary layer, which returns slowly to its initial stall condition, as observed in wind-tunnel experiments. A simple model of the impulse jet actuator used herein is found to be sufficient to represent the global effects of the jet on the stalled flow because it correctly represents the momentum injected into the flow. Advisors/Committee Members: Moser, Robert deLancey (advisor), Bogard, David G. (committee member), Ezekoye, Ofodike A. (committee member), Goldstein, David B. (committee member), Raman, Venkatramanan (committee member).

Subjects/Keywords: Flow control; Synthetic jet; Pulsed jet; Airfoils; Moving grids; Turbulence models

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Jee, Sol Keun, 1. (2010). Flow control simulation with synthetic and pulsed jet actuator. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2010-08-1676

Chicago Manual of Style (16^th Edition):

Jee, Sol Keun, 1979-. “Flow control simulation with synthetic and pulsed jet actuator.” 2010. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/ETD-UT-2010-08-1676.

MLA Handbook (7^th Edition):

Jee, Sol Keun, 1979-. “Flow control simulation with synthetic and pulsed jet actuator.” 2010. Web. 07 Mar 2021.

Vancouver:

Jee, Sol Keun 1. Flow control simulation with synthetic and pulsed jet actuator. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2010. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/ETD-UT-2010-08-1676.

Council of Science Editors:

Jee, Sol Keun 1. Flow control simulation with synthetic and pulsed jet actuator. [Doctoral Dissertation]. University of Texas – Austin; 2010. Available from: http://hdl.handle.net/2152/ETD-UT-2010-08-1676

		in
And / Or
		in
And / Or
		in
And / Or
		in

Open Access Theses and Dissertations