Staggered Semi-Implicit Hybrid Finite Volume/Finite Element Schemes for Turbulent and Non-Newtonian Flows

This paper presents a new family of semi-implicit hybrid finite volume/finite element schemes on edge-based staggered meshes for the numerical solution of the incompressible Reynolds-Averaged Navier–Stokes (RANS) equations in combination with the <inline-formula><math xmlns="http://www...

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Autores principales:	Saray Busto, Michael Dumbser, Laura Río-Martín
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	hybrid finite volume/finite element method semi-implicit schemes staggered unstructured and Cartesian meshes positivity preserving schemes incompressible RANS realizable <i>k</i> − <i>ε</i> turbulence model Mathematics QA1-939
Acceso en línea:	https://doaj.org/article/7b27aa41c6994065aa50f9c2c3e1b588
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spelling	oai:doaj.org-article:7b27aa41c6994065aa50f9c2c3e1b5882021-11-25T18:17:41ZStaggered Semi-Implicit Hybrid Finite Volume/Finite Element Schemes for Turbulent and Non-Newtonian Flows10.3390/math92229722227-7390https://doaj.org/article/7b27aa41c6994065aa50f9c2c3e1b5882021-11-01T00:00:00Zhttps://www.mdpi.com/2227-7390/9/22/2972https://doaj.org/toc/2227-7390This paper presents a new family of semi-implicit hybrid finite volume/finite element schemes on edge-based staggered meshes for the numerical solution of the incompressible Reynolds-Averaged Navier–Stokes (RANS) equations in combination with the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>k</mi><mo>−</mo><mi>ε</mi></mrow></semantics></math></inline-formula> turbulence model. The rheology for calculating the laminar viscosity coefficient under consideration in this work is the one of a non-Newtonian Herschel–Bulkley (power-law) fluid with yield stress, which includes the Bingham fluid and classical Newtonian fluids as special cases. For the spatial discretization, we use edge-based staggered unstructured simplex meshes, as well as staggered non-uniform Cartesian grids. In order to get a simple and computationally efficient algorithm, we apply an operator splitting technique, where the hyperbolic convective terms of the RANS equations are discretized explicitly at the aid of a Godunov-type finite volume scheme, while the viscous parabolic terms, the elliptic pressure terms and the stiff algebraic source terms of the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>k</mi><mo>−</mo><mi>ε</mi></mrow></semantics></math></inline-formula> model are discretized implicitly. For the discretization of the elliptic pressure Poisson equation, we use classical conforming <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mi mathvariant="script">P</mi><mn>1</mn></msup></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mi mathvariant="script">Q</mi><mn>1</mn></msup></semantics></math></inline-formula> finite elements on triangles and rectangles, respectively. The implicit discretization of the viscous terms is mandatory for non-Newtonian fluids, since the apparent viscosity can tend to infinity for fluids with yield stress and certain power-law fluids. It is carried out with <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mi mathvariant="script">P</mi><mn>1</mn></msup></semantics></math></inline-formula> finite elements on triangular simplex meshes and with finite volumes on rectangles. For Cartesian grids and more general orthogonal unstructured meshes, we can prove that our new scheme can preserve the <i>positivity</i> of <i>k</i> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ε</mi></semantics></math></inline-formula>. This is achieved via a special implicit discretization of the stiff algebraic relaxation source terms, using a suitable combination of the discrete evolution equations for the logarithms of <i>k</i> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ε</mi></semantics></math></inline-formula>. The method is applied to some classical academic benchmark problems for non-Newtonian and turbulent flows in two space dimensions, comparing the obtained numerical results with available exact or numerical reference solutions. In all cases, an excellent agreement is observed.Saray BustoMichael DumbserLaura Río-MartínMDPI AGarticlehybrid finite volume/finite element methodsemi-implicit schemesstaggered unstructured and Cartesian meshespositivity preserving schemesincompressible RANSrealizable <i>k</i> − <i>ε</i> turbulence modelMathematicsQA1-939ENMathematics, Vol 9, Iss 2972, p 2972 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	hybrid finite volume/finite element method semi-implicit schemes staggered unstructured and Cartesian meshes positivity preserving schemes incompressible RANS realizable <i>k</i> − <i>ε</i> turbulence model Mathematics QA1-939
spellingShingle	hybrid finite volume/finite element method semi-implicit schemes staggered unstructured and Cartesian meshes positivity preserving schemes incompressible RANS realizable <i>k</i> − <i>ε</i> turbulence model Mathematics QA1-939 Saray Busto Michael Dumbser Laura Río-Martín Staggered Semi-Implicit Hybrid Finite Volume/Finite Element Schemes for Turbulent and Non-Newtonian Flows
description	This paper presents a new family of semi-implicit hybrid finite volume/finite element schemes on edge-based staggered meshes for the numerical solution of the incompressible Reynolds-Averaged Navier–Stokes (RANS) equations in combination with the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>k</mi><mo>−</mo><mi>ε</mi></mrow></semantics></math></inline-formula> turbulence model. The rheology for calculating the laminar viscosity coefficient under consideration in this work is the one of a non-Newtonian Herschel–Bulkley (power-law) fluid with yield stress, which includes the Bingham fluid and classical Newtonian fluids as special cases. For the spatial discretization, we use edge-based staggered unstructured simplex meshes, as well as staggered non-uniform Cartesian grids. In order to get a simple and computationally efficient algorithm, we apply an operator splitting technique, where the hyperbolic convective terms of the RANS equations are discretized explicitly at the aid of a Godunov-type finite volume scheme, while the viscous parabolic terms, the elliptic pressure terms and the stiff algebraic source terms of the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>k</mi><mo>−</mo><mi>ε</mi></mrow></semantics></math></inline-formula> model are discretized implicitly. For the discretization of the elliptic pressure Poisson equation, we use classical conforming <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mi mathvariant="script">P</mi><mn>1</mn></msup></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mi mathvariant="script">Q</mi><mn>1</mn></msup></semantics></math></inline-formula> finite elements on triangles and rectangles, respectively. The implicit discretization of the viscous terms is mandatory for non-Newtonian fluids, since the apparent viscosity can tend to infinity for fluids with yield stress and certain power-law fluids. It is carried out with <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mi mathvariant="script">P</mi><mn>1</mn></msup></semantics></math></inline-formula> finite elements on triangular simplex meshes and with finite volumes on rectangles. For Cartesian grids and more general orthogonal unstructured meshes, we can prove that our new scheme can preserve the <i>positivity</i> of <i>k</i> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ε</mi></semantics></math></inline-formula>. This is achieved via a special implicit discretization of the stiff algebraic relaxation source terms, using a suitable combination of the discrete evolution equations for the logarithms of <i>k</i> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ε</mi></semantics></math></inline-formula>. The method is applied to some classical academic benchmark problems for non-Newtonian and turbulent flows in two space dimensions, comparing the obtained numerical results with available exact or numerical reference solutions. In all cases, an excellent agreement is observed.
format	article
author	Saray Busto Michael Dumbser Laura Río-Martín
author_facet	Saray Busto Michael Dumbser Laura Río-Martín
author_sort	Saray Busto
title	Staggered Semi-Implicit Hybrid Finite Volume/Finite Element Schemes for Turbulent and Non-Newtonian Flows
title_short	Staggered Semi-Implicit Hybrid Finite Volume/Finite Element Schemes for Turbulent and Non-Newtonian Flows
title_full	Staggered Semi-Implicit Hybrid Finite Volume/Finite Element Schemes for Turbulent and Non-Newtonian Flows
title_fullStr	Staggered Semi-Implicit Hybrid Finite Volume/Finite Element Schemes for Turbulent and Non-Newtonian Flows
title_full_unstemmed	Staggered Semi-Implicit Hybrid Finite Volume/Finite Element Schemes for Turbulent and Non-Newtonian Flows
title_sort	staggered semi-implicit hybrid finite volume/finite element schemes for turbulent and non-newtonian flows
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/7b27aa41c6994065aa50f9c2c3e1b588
work_keys_str_mv	AT saraybusto staggeredsemiimplicithybridfinitevolumefiniteelementschemesforturbulentandnonnewtonianflows AT michaeldumbser staggeredsemiimplicithybridfinitevolumefiniteelementschemesforturbulentandnonnewtonianflows AT laurariomartin staggeredsemiimplicithybridfinitevolumefiniteelementschemesforturbulentandnonnewtonianflows
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Staggered Semi-Implicit Hybrid Finite Volume/Finite Element Schemes for Turbulent and Non-Newtonian Flows

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