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University of Kansas
1.
LIiu, Yangliu.
Vortical Flow Effects on Flow Separation Control.
Degree: MS, Aerospace Engineering, 2016, University of Kansas
URL: http://hdl.handle.net/1808/23991 
► The effect of Reynolds number, oscillation frequency, amplitude, and the incident angle on flow separation control is studied numerically in this thesis. Two configurations are…
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▼ The effect of Reynolds number, oscillation frequency, amplitude, and the incident angle on flow separation control is studied numerically in this thesis. Two configurations are investigated, cylinders in tandem and the cylinder-airfoil arrangement. The upstream cylinder changes locations, size, and oscillating frequencies and amplitudes, which necessitates investigating its effect on separation control of the downstream cylinder or airfoil. A validation simulation based on an airfoil in the wake of a stationary cylinder is carried out to verify the numerical method that will be used in this study. The results show that high-Reynolds-number, high-frequency low-amplitude oscillation motion of the upstream cylinder reduces the flow separation on the downstream airfoil. By placing an oscillating cylinder in the upstream, the flow separation point moves slightly further downstream even at zero angles of attack.
Advisors/Committee Members: Zheng, Zhongquan Charlie (advisor), Taghavi, Ray (cmtemember), Wang, Zhijian (cmtemember).
Subjects/Keywords: Aerospace engineering; Engineering; Flow over cylinder and airfoil; Flow over tandem cylinders; Flow separation control; Vortical flow effct
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APA (6th Edition):
LIiu, Y. (2016). Vortical Flow Effects on Flow Separation Control. (Masters Thesis). University of Kansas. Retrieved from http://hdl.handle.net/1808/23991
Chicago Manual of Style (16th Edition):
LIiu, Yangliu. “Vortical Flow Effects on Flow Separation Control.” 2016. Masters Thesis, University of Kansas. Accessed January 17, 2021.
http://hdl.handle.net/1808/23991.
MLA Handbook (7th Edition):
LIiu, Yangliu. “Vortical Flow Effects on Flow Separation Control.” 2016. Web. 17 Jan 2021.
Vancouver:
LIiu Y. Vortical Flow Effects on Flow Separation Control. [Internet] [Masters thesis]. University of Kansas; 2016. [cited 2021 Jan 17].
Available from: http://hdl.handle.net/1808/23991.
Council of Science Editors:
LIiu Y. Vortical Flow Effects on Flow Separation Control. [Masters Thesis]. University of Kansas; 2016. Available from: http://hdl.handle.net/1808/23991
University of Kansas
2.
Weingart, Robert.
On-Track Testing as a Validation Method of Computational Fluid Dynamic Simulations of a Formula SAE Vehicle.
Degree: M.E., Mechanical Engineering, 2015, University of Kansas
URL: http://hdl.handle.net/1808/19383
► This thesis is about the validation of a computational fluid dynamics simulation of a ground vehicle by means of a low-budget coast-down test. The vehicle…
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▼ This thesis is about the validation of a computational fluid dynamics simulation of a ground vehicle by means of a low-budget coast-down test. The vehicle is built to the standards of the 2014 Formula SAE rules. It is equipped with large wings in the front and rear of the car; the vertical loads on the tires are measured by specifically calibrated shock potentiometers. The coast-down test was performed on a runway of a local airport and is used to determine vehicle specific coefficients such as drag, downforce, aerodynamic balance, and rolling resistance for different aerodynamic setups. The test results are then compared to the respective simulated results. The drag deviates about 5% from the simulated to the measured results. The downforce numbers show a deviation up to 18% respectively. Moreover, a sensitivity analysis of inlet velocities, ride heights, and pitch angles was performed with the help of the computational simulation.
Advisors/Committee Members: Sorem, Robert M (advisor), Tenpas, Peter W (cmtemember), Zheng, Zhongquan (Charlie) (cmtemember).
Subjects/Keywords: Mechanical engineering; Aerospace engineering; Analysis; CFD-Simulation; Coast-Down Test; External Aerodynamics; FSAE; Validation
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APA (6th Edition):
Weingart, R. (2015). On-Track Testing as a Validation Method of Computational Fluid Dynamic Simulations of a Formula SAE Vehicle. (Masters Thesis). University of Kansas. Retrieved from http://hdl.handle.net/1808/19383
Chicago Manual of Style (16th Edition):
Weingart, Robert. “On-Track Testing as a Validation Method of Computational Fluid Dynamic Simulations of a Formula SAE Vehicle.” 2015. Masters Thesis, University of Kansas. Accessed January 17, 2021.
http://hdl.handle.net/1808/19383.
MLA Handbook (7th Edition):
Weingart, Robert. “On-Track Testing as a Validation Method of Computational Fluid Dynamic Simulations of a Formula SAE Vehicle.” 2015. Web. 17 Jan 2021.
Vancouver:
Weingart R. On-Track Testing as a Validation Method of Computational Fluid Dynamic Simulations of a Formula SAE Vehicle. [Internet] [Masters thesis]. University of Kansas; 2015. [cited 2021 Jan 17].
Available from: http://hdl.handle.net/1808/19383.
Council of Science Editors:
Weingart R. On-Track Testing as a Validation Method of Computational Fluid Dynamic Simulations of a Formula SAE Vehicle. [Masters Thesis]. University of Kansas; 2015. Available from: http://hdl.handle.net/1808/19383
University of Kansas
3.
Li, Wen.
TIME DOMAIN SIMULATION FOR SOUND PROPAGATION OVER VARIOUS OBJECTS AND UNDER VORTICAL BACKGROUND CONDITIONS.
Degree: MS, Aerospace Engineering, 2015, University of Kansas
URL: http://hdl.handle.net/1808/23960
► Acoustic wave propagations have been studied for a long time with both experimental and numerical methods. Most of the analytical solutions for wave propagations are…
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▼ Acoustic wave propagations have been studied for a long time with both experimental and numerical methods. Most of the analytical solutions for wave propagations are considered for simple environments such as a homogeneous atmospheres. As a result, the analytical solutions are unable to be applied for complicated environments. Numerical methods have become more and more important in acoustics studies after decades of development. The finite difference time-domain method (FDTD) is one of the most commonly used numerical methods in wave propagation studies. Compared with the other methods, the FDTD method is able to include many aspects of sound wave behaviors such as reflection, refraction, and diffraction in the physical problems. In this thesis, the linearized acoustic Euler equations coupled with the immersed boundary method are applied to investigate the sound wave propagation over complex environments. For the three-dimensional simulations of sound wave propagation in long distance, the moving domain method and parallel computing techniques are applied. Based on these approaches, the computational costs are significantly reduced and the simulation efficiency is greatly improved. When looking into the effects of high subsonic vortical flow, a high order WENO scheme is applied for the simulation. In this way the simulation stability can be achieved and the sound scattering of vortical flow can be studied. Then, the numerical scheme is applied to simulate an ultrasonic plane wave propagating through biological tissue. The linearized Euler acoustic equations coupled with the spatial fractional Laplacian operators are used for numerical simulations. The absorption and attenuation effects of the biological lossy media are successfully observed from the simulation results. Throughout this thesis, the simulation results are compared with either experimental measurements or analytical solutions so that the accuracy of the implemented numerical scheme is validated.
Advisors/Committee Members: Zheng, Zhongquan Charlie (advisor), Farokhi, Saeed (cmtemember), Taghavi, Ray (cmtemember).
Subjects/Keywords: Aerospace engineering
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APA ·
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APA (6th Edition):
Li, W. (2015). TIME DOMAIN SIMULATION FOR SOUND PROPAGATION OVER VARIOUS OBJECTS AND UNDER VORTICAL BACKGROUND CONDITIONS. (Masters Thesis). University of Kansas. Retrieved from http://hdl.handle.net/1808/23960
Chicago Manual of Style (16th Edition):
Li, Wen. “TIME DOMAIN SIMULATION FOR SOUND PROPAGATION OVER VARIOUS OBJECTS AND UNDER VORTICAL BACKGROUND CONDITIONS.” 2015. Masters Thesis, University of Kansas. Accessed January 17, 2021.
http://hdl.handle.net/1808/23960.
MLA Handbook (7th Edition):
Li, Wen. “TIME DOMAIN SIMULATION FOR SOUND PROPAGATION OVER VARIOUS OBJECTS AND UNDER VORTICAL BACKGROUND CONDITIONS.” 2015. Web. 17 Jan 2021.
Vancouver:
Li W. TIME DOMAIN SIMULATION FOR SOUND PROPAGATION OVER VARIOUS OBJECTS AND UNDER VORTICAL BACKGROUND CONDITIONS. [Internet] [Masters thesis]. University of Kansas; 2015. [cited 2021 Jan 17].
Available from: http://hdl.handle.net/1808/23960.
Council of Science Editors:
Li W. TIME DOMAIN SIMULATION FOR SOUND PROPAGATION OVER VARIOUS OBJECTS AND UNDER VORTICAL BACKGROUND CONDITIONS. [Masters Thesis]. University of Kansas; 2015. Available from: http://hdl.handle.net/1808/23960
4.
Karwas, Alex A.
An Unconditionally Stable Method for Numerically Solving Solar Sail Spacecraft Equations of Motion.
Degree: PhD, Aerospace Engineering, 2015, University of Kansas
URL: http://hdl.handle.net/1808/19374
► Solar sails use the endless supply of the Sun's radiation to propel spacecraft through space. The sails use the momentum transfer from the impinging solar…
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▼ Solar sails use the endless supply of the Sun's radiation to propel spacecraft through space. The sails use the momentum transfer from the impinging solar radiation to provide thrust to the spacecraft while expending zero fuel. Recently, the first solar sail spacecraft, or sailcraft, named IKAROS completed a successful mission to Venus and proved the concept of solar sail propulsion. Sailcraft experimental data is difficult to gather due to the large expenses of space travel, therefore, a reliable and accurate computational method is needed to make the process more efficient. Presented in this document is a new approach to simulating solar sail spacecraft trajectories. The new method provides unconditionally stable numerical solutions for trajectory propagation and includes an improved physical description over other methods. The unconditional stability of the new method means that a unique numerical solution is always determined. The improved physical description of the trajectory provides a numerical solution and time derivatives that are continuous throughout the entire trajectory. The error of the continuous numerical solution is also known for the entire trajectory. Optimal control for maximizing thrust is also provided within the framework of the new method. Verification of the new approach is presented through a mathematical description and through numerical simulations. The mathematical description provides details of the sailcraft equations of motion, the numerical method used to solve the equations, and the formulation for implementing the equations of motion into the numerical solver. Previous work in the field is summarized to show that the new approach can act as a replacement to previous trajectory propagation methods. A code was developed to perform the simulations and it is also described in this document. Results of the simulations are compared to the flight data from the IKAROS mission. Comparison of the two sets of data show that the new approach is capable of accurately simulating sailcraft motion. Sailcraft and spacecraft simulations are compared to flight data and to other numerical solution techniques. The new formulation shows an increase in accuracy over a widely used trajectory propagation technique. Simulations for two-dimensional, three-dimensional, and variable attitude trajectories are presented to show the multiple capabilities of the new technique. An element of optimal control is also part of the new technique. An additional equation is added to the sailcraft equations of motion that maximizes thrust in a specific direction. A technical description and results of an example optimization problem are presented. The spacecraft attitude dynamics equations take the simulation a step further by providing control torques using the angular rate and acceleration outputs of the numerical formulation.
Advisors/Committee Members: Taghavi, Ray (advisor), Farokhi, Saeed (cmtemember), Keshmiri, Shawn (cmtemember), Zheng, Zhongquan Charlie (cmtemember), Yimer, Bedru (cmtemember).
Subjects/Keywords: Aerospace engineering; Finite Element Method; Propagation; Sailcraft; Solar Sail; Spacecraft; Trajectory
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APA ·
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APA (6th Edition):
Karwas, A. A. (2015). An Unconditionally Stable Method for Numerically Solving Solar Sail Spacecraft Equations of Motion. (Doctoral Dissertation). University of Kansas. Retrieved from http://hdl.handle.net/1808/19374
Chicago Manual of Style (16th Edition):
Karwas, Alex A. “An Unconditionally Stable Method for Numerically Solving Solar Sail Spacecraft Equations of Motion.” 2015. Doctoral Dissertation, University of Kansas. Accessed January 17, 2021.
http://hdl.handle.net/1808/19374.
MLA Handbook (7th Edition):
Karwas, Alex A. “An Unconditionally Stable Method for Numerically Solving Solar Sail Spacecraft Equations of Motion.” 2015. Web. 17 Jan 2021.
Vancouver:
Karwas AA. An Unconditionally Stable Method for Numerically Solving Solar Sail Spacecraft Equations of Motion. [Internet] [Doctoral dissertation]. University of Kansas; 2015. [cited 2021 Jan 17].
Available from: http://hdl.handle.net/1808/19374.
Council of Science Editors:
Karwas AA. An Unconditionally Stable Method for Numerically Solving Solar Sail Spacecraft Equations of Motion. [Doctoral Dissertation]. University of Kansas; 2015. Available from: http://hdl.handle.net/1808/19374
5.
Zhou, Cheng.
Adaptive High-Order Discretization of the Reynolds-Averaged Navier-Stokes(RANS) Equations.
Degree: PhD, Aerospace Engineering, 2016, University of Kansas
URL: http://hdl.handle.net/1808/24139
► The use of high-order methods to compute turbulent flows governed by the Reynolds- averaged Navier-Stokes (RANS) equations is an active research topic in the compu-…
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▼ The use of high-order methods to compute turbulent flows governed by the Reynolds- averaged Navier-Stokes (RANS) equations is an active research topic in the compu- tational fluid dynamics (CFD) community. However, it is well known that high-order methods for the non-smooth turbulence modeling equations are difficult to converge to the steady-state because of the numerical stiffness. The objective of this work is to de- velop a robust and efficient high-order discretization that can simulate turbulent flows governed by the Reynolds-Averaged Navier-Stokes equations, which involves the de- velopment of high-order space discretization of robust turbulence modeling equations, the improvement of time integration strategy, and the application of effective mesh adaptation methods. In the present study, correction procedure via reconstruction (CPR) high-order dis- cretization is developed to solve the Reynolds-averaged Navier-Stokes (RANS) equa- tions with the modified Spalart and Allmaras (SA) model. In this model, the non- dimensional length scale depends on the distance to the nearest wall. To compute the distance of each solution point in the domain to the nearest curved polynomial wall boundaries, the CPR high-order discretization is extended to solve the Eikonal equa- tion. On the other hand, to improve time integration strategy for the simulation of turbulent flows, the present work carried out a comparative study of several implicit time integration schemes to determine which is the most efficient, robust and general scheme. Additionally, an adjoint-based adaptive mesh refinement method is utilized to minimize the output error. Numerical results show that, to achieve a certain level of accuracy, the adaptive CPR discretization of the RANS equations with the SA model saves orders of magnitude in terms of number of degrees of freedom comparing to the numerical results of uniform mesh refinement, when applied to the simulations of turbulent flows.
Advisors/Committee Members: Wang, Z.J. (advisor), Farokhi, Saeed (cmtemember), Taghavi, Ray (cmtemember), Tu, Xuemin (cmtemember), Zheng, Zhongquan Charlie (cmtemember).
Subjects/Keywords: Aerospace engineering; Mathematics; Adaptive; CFD; CPR; High-order method; RANS
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APA ·
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APA (6th Edition):
Zhou, C. (2016). Adaptive High-Order Discretization of the Reynolds-Averaged Navier-Stokes(RANS) Equations. (Doctoral Dissertation). University of Kansas. Retrieved from http://hdl.handle.net/1808/24139
Chicago Manual of Style (16th Edition):
Zhou, Cheng. “Adaptive High-Order Discretization of the Reynolds-Averaged Navier-Stokes(RANS) Equations.” 2016. Doctoral Dissertation, University of Kansas. Accessed January 17, 2021.
http://hdl.handle.net/1808/24139.
MLA Handbook (7th Edition):
Zhou, Cheng. “Adaptive High-Order Discretization of the Reynolds-Averaged Navier-Stokes(RANS) Equations.” 2016. Web. 17 Jan 2021.
Vancouver:
Zhou C. Adaptive High-Order Discretization of the Reynolds-Averaged Navier-Stokes(RANS) Equations. [Internet] [Doctoral dissertation]. University of Kansas; 2016. [cited 2021 Jan 17].
Available from: http://hdl.handle.net/1808/24139.
Council of Science Editors:
Zhou C. Adaptive High-Order Discretization of the Reynolds-Averaged Navier-Stokes(RANS) Equations. [Doctoral Dissertation]. University of Kansas; 2016. Available from: http://hdl.handle.net/1808/24139
6.
Blanco, Rafael Rodriguez.
Performance Analysis of an Annular Diffuser Under the Influence of a Gas Turbine Stage Exit Flow.
Degree: MS, Aerospace Engineering, 2013, University of Kansas
URL: http://hdl.handle.net/1808/12960
► In this investigation the performance of a gas turbine exhaust diffuser subject to the outlet flow conditions of a turbine stage is evaluated. Towards that…
(more)
▼ In this investigation the performance of a gas turbine exhaust diffuser subject to the outlet flow conditions of a turbine stage is evaluated. Towards that goal, a fully three-dimensional computational analysis has been performed where several turbine stage-exhaust diffuser configurations have been studied: a turbine stage with a shrouded rotor coupled to a diffuser with increasing divergence angle in the diffuser, and a turbine stage with an unshrouded rotor was also considered for the exhaust diffuser performance analysis. The large load of this investigation was evaluated using a steady state numerical analysis utilizing the "mixing plane" algorithm between the rotating rotor and stationary stator and diffuser rows. Finally, an unsteady analysis is performed on a turbine stage with an unsrhouded rotor coupled to an annular exhaust diffuser with an outer wall opening angle of 18°. It has been found that the over the tip leakage flow in the unshrouded rotor emerges as a swirling wall jet at the upper wall of the diffuser. When using the turbine with the shrouded rotor no wall jet was observed, making the flow at the entrance to the diffuser "quasi-uniform". The maximum opening angle of the diffuser upper wall achieved before the diffuser stalls was 12° with a static pressure recovery coefficient of Cp = 0.293. When the wall jet was observed, diffuser opening angles of 18° were possible with a static pressure recovery of Cp = 0.365. Consequently the wall jet energizes the diffuser upper wall boundary layer flow, allows for higher static pressure recovery levels and postpones diffuser stall. By altering the speed of the rotor the effect of the swirl in the turbine exit plane on the performance of the diffuser was explored. In the case where the wall jet was absent the diffuser recovers more pressure when the inlet is swirl-free. In this case the performance of the diffuser is independent on whether the turbine exit flow has co or counter swirl. In the presence of the wall jet, higher static pressure recovery was achieved when the wall jet was in co-swirl and the core flow at a slightly counter-swirl direction. This observation was more pronounced when larger diffuser upper wall opening angles were considered. In the unsteady analysis it was found that the wall jet axial velocity and swirl intensities pulsate with the relative position of the rotor to the stator. The wall jet is always co-swirling while the core flow is counter-swirling. Moreover, the wall jet does not penetrate the diffuser boundary layer as deeply as was observed in the steady state case and flow separation occurs at the upper endwall corner of the diffuser. Furthermore the performance of the diffuser shows a periodic variation that seems to depend on the relative position of the rotor to the stator. The averaged pressure recovery coefficient is Cp = 0.321 which is 11.0 % less than predicted in the steady state case.
Advisors/Committee Members: Farokhi, Saeed (advisor), Taghavi, Ray (cmtemember), Zheng, Zhongquan Charlie (cmtemember).
Subjects/Keywords: Aerospace engineering; Mechanical engineering; Diffuser; Over the tip leakage; Swirl; Turbine; Wall jet
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APA ·
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APA (6th Edition):
Blanco, R. R. (2013). Performance Analysis of an Annular Diffuser Under the Influence of a Gas Turbine Stage Exit Flow. (Masters Thesis). University of Kansas. Retrieved from http://hdl.handle.net/1808/12960
Chicago Manual of Style (16th Edition):
Blanco, Rafael Rodriguez. “Performance Analysis of an Annular Diffuser Under the Influence of a Gas Turbine Stage Exit Flow.” 2013. Masters Thesis, University of Kansas. Accessed January 17, 2021.
http://hdl.handle.net/1808/12960.
MLA Handbook (7th Edition):
Blanco, Rafael Rodriguez. “Performance Analysis of an Annular Diffuser Under the Influence of a Gas Turbine Stage Exit Flow.” 2013. Web. 17 Jan 2021.
Vancouver:
Blanco RR. Performance Analysis of an Annular Diffuser Under the Influence of a Gas Turbine Stage Exit Flow. [Internet] [Masters thesis]. University of Kansas; 2013. [cited 2021 Jan 17].
Available from: http://hdl.handle.net/1808/12960.
Council of Science Editors:
Blanco RR. Performance Analysis of an Annular Diffuser Under the Influence of a Gas Turbine Stage Exit Flow. [Masters Thesis]. University of Kansas; 2013. Available from: http://hdl.handle.net/1808/12960
. 
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