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You searched for subject:(Multirate scheme). Showing records 1 – 3 of 3 total matches.

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University of Manitoba

1. Kotovshchikova, Marina. On a third-order FVTD scheme for three-dimensional Maxwell's Equations.

Degree: Mathematics, 2016, University of Manitoba

This thesis considers the application of the type II third order WENO finite volume reconstruction for unstructured tetrahedral meshes proposed by Zhang and Shu in (CCP, 2009) and the third order multirate Runge-Kutta time-stepping to the solution of Maxwell's equations. The dependance of accuracy of the third order WENO scheme on the small parameter in the definition of non-linear weights is studied in detail for one-dimensional uniform meshes and numerical results confirming the theoretical analysis are presented for the linear advection equation. This analysis is found to be crucial in the design of the efficient three-dimensional WENO scheme, full details of which are presented. Several multirate Runge-Kutta (MRK) schemes which advance the solution with local time-steps assigned to different multirate groups are studied. Analysis of accuracy of three different MRK approaches for linear problems based on classic order-conditions is presented. The most flexible and efficient multirate schemes based on works by Tang and Warnecke (JCM, 2006) and Liu, Li and Hu (JCP, 2010) are implemented in three-dimensional finite volume time-domain (FVTD) method. The main characteristics of chosen MRK schemes are flexibility in defining the time-step ratios between multirate groups and consistency of the scheme. Various approaches to partition the three-dimensional computational domain into multirate groups to maximize the achievable speedup are discussed. Numerical experiments with three-dimensional electromagnetic problems are presented to validate the performance of the proposed FVTD method. Three-dimensional results agree with theoretical and numerical accuracy analysis performed for the one-dimensional case. The proposed implementation of multirate schemes demonstrates greater speedup than previously reported in literature. Advisors/Committee Members: Lui, Shaun (Mathematics) (supervisor), Guo, Benqi (Mathematics) .

Subjects/Keywords: Maxwell's equations; Finite volume method; Unstructured tetrahedral mesh; WENO scheme; Multirate Runge-Kutta scheme

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APA (6th Edition):

Kotovshchikova, M. (2016). On a third-order FVTD scheme for three-dimensional Maxwell's Equations. (Thesis). University of Manitoba. Retrieved from http://hdl.handle.net/1993/31035

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Kotovshchikova, Marina. “On a third-order FVTD scheme for three-dimensional Maxwell's Equations.” 2016. Thesis, University of Manitoba. Accessed April 10, 2021. http://hdl.handle.net/1993/31035.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Kotovshchikova, Marina. “On a third-order FVTD scheme for three-dimensional Maxwell's Equations.” 2016. Web. 10 Apr 2021.

Vancouver:

Kotovshchikova M. On a third-order FVTD scheme for three-dimensional Maxwell's Equations. [Internet] [Thesis]. University of Manitoba; 2016. [cited 2021 Apr 10]. Available from: http://hdl.handle.net/1993/31035.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Kotovshchikova M. On a third-order FVTD scheme for three-dimensional Maxwell's Equations. [Thesis]. University of Manitoba; 2016. Available from: http://hdl.handle.net/1993/31035

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

2. Itam, Emmanuelle. Simulation numérique d'écoulements autour de corps non profilés par des modèles de turbulence hybrides et un schéma multirate : Numerical simulation of flows around bluff bodies with hybrid models and a multirate scheme.

Degree: Docteur es, Mathématiques et modélisation, 2017, Montpellier

Ce travail est une contribution à la simulation numérique d'écoulements turbulents autour de corps non profilés. Après avoir précisé les ingrédients numériques et les modèles de turbulence utilisés dans nos simulations, nous présentons une étude sur l'évaluation des effets de la procédure dynamique des modèles de sous-maille dans un modèle VMS-LES et une approche hybride RANS/VMS-LES. Des problèmes d'écoulements autour d'un cylindre seul et en tandem sont considérés. Nous étudions ensuite le comportement de modèles de turbulence hybrides pour la simulation d'écoulements en régime sous-critique autour d'un cylindre circulaire. Le calcul de l'écoulement autour d'un cylindre de section rectangulaire par l'approche VMS-LES est aussi présenté. Enfin, dans une dernière partie, après avoir fait une revue des travaux importants sur les schémas d'avancement en temps multirate, nous proposons une nouvelle approche explicite multirate par agglomération de volumes finis que nous appliquons à des calculs d'écoulements turbulents complexes en utilisant un modèle de turbulence hybride.

This work is a contribution to the numerical simulation of turbulent flows around bluff bodies. After specifying the numerical ingredients and the turbulence models used in our simulations, we present a study on the impact of the dynamic sub-grid scale modeling in VMS-LES model and a RANS/VMS-LES hybrid turbulence approach. Simulations of flows around a cylinder and a tandem are performed. Next, we assess the behaviour of some hybrid turbulence models for the simulation of flows around a circular cylinder in the subcritical regime. The computation of the flow around a rectangular cylinder with the VMS-LES approach is also presented. At last, after a review of some important works on multirate time advancing schemes, we propose a new volume-agglomeration explicit multirate approach that is applied to the computation of complex turbulent flows by a hybrid turbulence model.

Advisors/Committee Members: Koobus, Bruno (thesis director).

Subjects/Keywords: Eléments finis/volumes finis; Maillage non structuré; Vms-Les; Modèles de turbulence hybrides; Cylindre seul et cylindres en tandem; Schéma multirate; Finite element/finite volume; Unstructured grid; Vms-Les; Hybrid turbulence model; Single cylinder and cylinders in tandem; Multirate scheme

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

APA (6th Edition):

Itam, E. (2017). Simulation numérique d'écoulements autour de corps non profilés par des modèles de turbulence hybrides et un schéma multirate : Numerical simulation of flows around bluff bodies with hybrid models and a multirate scheme. (Doctoral Dissertation). Montpellier. Retrieved from http://www.theses.fr/2017MONTS049

Chicago Manual of Style (16th Edition):

Itam, Emmanuelle. “Simulation numérique d'écoulements autour de corps non profilés par des modèles de turbulence hybrides et un schéma multirate : Numerical simulation of flows around bluff bodies with hybrid models and a multirate scheme.” 2017. Doctoral Dissertation, Montpellier. Accessed April 10, 2021. http://www.theses.fr/2017MONTS049.

MLA Handbook (7th Edition):

Itam, Emmanuelle. “Simulation numérique d'écoulements autour de corps non profilés par des modèles de turbulence hybrides et un schéma multirate : Numerical simulation of flows around bluff bodies with hybrid models and a multirate scheme.” 2017. Web. 10 Apr 2021.

Vancouver:

Itam E. Simulation numérique d'écoulements autour de corps non profilés par des modèles de turbulence hybrides et un schéma multirate : Numerical simulation of flows around bluff bodies with hybrid models and a multirate scheme. [Internet] [Doctoral dissertation]. Montpellier; 2017. [cited 2021 Apr 10]. Available from: http://www.theses.fr/2017MONTS049.

Council of Science Editors:

Itam E. Simulation numérique d'écoulements autour de corps non profilés par des modèles de turbulence hybrides et un schéma multirate : Numerical simulation of flows around bluff bodies with hybrid models and a multirate scheme. [Doctoral Dissertation]. Montpellier; 2017. Available from: http://www.theses.fr/2017MONTS049

3. -5603-2533. Efficient algorithms for flow models coupled with geomechanics for porous media applications.

Degree: PhD, Computational Science, Engineering, and Mathematics, 2016, University of Texas – Austin

The coupling between subsurface flow and reservoir geomechanics plays a critical role in obtaining accurate results for models involving reservoir deformation, surface subsidence, well stability, sand production, waste deposition, hydraulic fracturing, CO₂ sequestration, and hydrocarbon recovery. From a pure computational point of view, such a coupling can be quite a challenging and complicated task. This stems from the fact that the constitutive equations governing geomechanical deformations are different in nature from those governing porous media flow. The geomechanical effects account for the influence of deformations in the porous media caused due to the pore pressure and can be very important especially in the case of stress-sensitive and fractured reservoirs. Considering that fractures are very much prevalent in the porous media and they have strong influence on the flow profiles, it is important to study coupled geomechanics and flow problems in fractured reservoirs. In this work, we pursue three main objectives: first, to rigorously design and analyze iterative and explicit coupling algorithms for coupling flow and geomechanics in both poro-elasitc and fractured poro-elastic reservoirs. The analysis of iterative coupling schemes relies on studying the equations satisfied by the difference of iterates and using a Banach contraction argument to derive geometric convergence (Banach fixed-point contraction) results. The analysis of explicit coupling schemes result in analogous stability estimates. In this work, conformal Galerkin is used for mechanics, and a mixed formulation, including the Multipoint Flux Mixed Finite Element method as a special case, is used for the flow model. For fractured poro-elastic media, our iteratively coupled schemes are adaptations, due to the presence of fractures, of the classical fixed stress-splitting scheme, in which fractures are treated as possibly non-planar interfaces. The second main objective in this work is to exploit the different time scales of the mechanics and flow problems. Due to its physical nature, the geomechanics problem can cope with a coarser time step compared to the flow problem. This makes the multirate coupling scheme, the one in which the flow problem takes several (finer) time steps within the same coarse mechanics time step, a natural candidate in this setting. Inspired by that, we rigorously formulate and analyze convergence properties of both multirate iterative and explicit coupling schemes in both poro-elastic and fractured poro-elastic reservoirs. In addition, our theoretically derived Banach contraction estimates are validated against numerical simulations. The third objective in this work is to optimize the solution strategy of the nonlinear flow model in coupled flow and mechanics schemes. The global inexact Newton method, combined with the line search backtracking algorithm along with heuristic forcing functions, can be efficiently employed to reduce the number of flow linear iterations, and hence, the overall CPU run time. We first validate… Advisors/Committee Members: Wheeler, Mary F. (Mary Fanett) (advisor), Arbogast, Todd (committee member), Demkowicz, Leszek F. (committee member), Delshad, Mojdeh (committee member), Dhillon, Inderjit (committee member), Kumar, Kundan (committee member).

Subjects/Keywords: Poroelasticity; Biot system; Fixed-stress split iterative coupling; Undrained split iterative coupling; Explicit coupling; Single rate scheme; Multirate scheme; Banach fixed-point contraction; Fractured poroelastic media; A priori error estiamtes; Global inexact Newton methods

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

APA (6th Edition):

-5603-2533. (2016). Efficient algorithms for flow models coupled with geomechanics for porous media applications. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/46503

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

Chicago Manual of Style (16th Edition):

-5603-2533. “Efficient algorithms for flow models coupled with geomechanics for porous media applications.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed April 10, 2021. http://hdl.handle.net/2152/46503.

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

MLA Handbook (7th Edition):

-5603-2533. “Efficient algorithms for flow models coupled with geomechanics for porous media applications.” 2016. Web. 10 Apr 2021.

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

Vancouver:

-5603-2533. Efficient algorithms for flow models coupled with geomechanics for porous media applications. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2021 Apr 10]. Available from: http://hdl.handle.net/2152/46503.

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

Council of Science Editors:

-5603-2533. Efficient algorithms for flow models coupled with geomechanics for porous media applications. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/46503

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

.