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A Novel Diffuse-Interface Model and Numerical Methods for Compressible Turbulent Two-Phase Flows and Scalar Transport.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	A Novel Diffuse-Interface Model and Numerical Methods for Compressible Turbulent Two-Phase Flows and Scalar Transport./
作者:	Suresh, Suhas Jain.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
面頁冊數:	180 p.
附註:	Source: Dissertations Abstracts International, Volume: 83-09, Section: B.
Contained By:	Dissertations Abstracts International83-09B.
標題:	Numerical analysis. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29003859
ISBN:	9798209784135

A Novel Diffuse-Interface Model and Numerical Methods for Compressible Turbulent Two-Phase Flows and Scalar Transport.
Suresh, Suhas Jain.

A Novel Diffuse-Interface Model and Numerical Methods for Compressible Turbulent Two-Phase Flows and Scalar Transport. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 180 p.

Source: Dissertations Abstracts International, Volume: 83-09, Section: B.

Thesis (Ph.D.)--Stanford University, 2021.

This item must not be sold to any third party vendors.

Compressible two-phase flows and the transport of scalars in two-phase flows have a wide range of applications in natural and engineering processes. In this thesis, we first propose a novel diuseinterface model for the simulation of compressible two-phase flows. We start with the baseline five-equation model that consists of equations for the transport of volume fraction, mass of each phase, momentum, and total energy. It is known that this model cannot be used with a nondissipative scheme as is, and the direct solution of these equations with a dissipative scheme results in artificial diusion of the interface, which results in poor accuracy. We therefore, propose adding interface-regularization (diusion-sharpening) terms to this five-equation model in such a way that the resulting model can now be used with a non-dissipative central scheme, and the model also maintains the discrete conservation of mass of each phase, momentum, and total energy of the system. We also show that the proposed interface-regularization terms in the model do not spuriously contribute to the total kinetic energy of the system and approximately satisfies the conservation of entropy, and therefore, do not aect the non-linear stability of the numerical simulation. However, it is also important to satisfy these conditions discretely.For a compressible flow, it is known that the discrete conservation of kinetic energy, in the absence of dissipative mechanisms, alone is not a sucient condition for numerical stability, unlike in incompressible flows. For stable numerical simulations of compressible flows, a discrete entropy condition needs to be satisfied. To achieve this, we first propose discrete consistency conditions between the numerical fluxes, and then present a set of numerical fluxes-which satisfies these consistency conditions-that results in an exact conservation of kinetic energy and approximate conservation of entropy (a KEEP scheme) in the absence of pressure work, viscosity, thermal di↵usion e↵ects, and time di↵erencing errors.As part of verification and validation, we present numerical simulations using the model and compare the results with the existing models in the literature to assess: (a) the accuracy of evolution of the interface shape, (b) the ability of the model to maintain constant interface thickness, (c) the ability to maintain conservation properties, (d) implementation of surface tension e↵ects, (e) propagation of acoustics and their interaction with material interfaces, (f) the accuracy and robustness of the numerical scheme for the simulation of high-Reynolds-number turbulent flows, and (g) performance and scalability of the method. We also present coarse-grid numerical simulations of compressible single-phase and two-phase turbulent flows at infinite Re, to illustrate the stability of the proposed method in canonical test cases, such as isotropic turbulence and Taylor-Green vortex flows. A resolved simulation of a droplet-laden isotropic turbulence is also presented at finite Re, and the e↵ect of the presence of droplets on the flow is analyzed.We also propose a novel scalar-transport model for the simulation of scalar quantities in two-phase flows. In a two-phase flow, the scalar quantities typically have disparate properties in two phases, which results in e↵ective confinement of the scalar quantities in one of the phases, in the time scales of interest. This confinement of the scalars lead to the formation of sharp gradients of the scalar concentration values at the interface, presenting a serious challenge for its numerical simulations. To overcome this challenge, we propose a new model for the transport of scalars in two-phase flows. The provable strengths of the proposed model are: (a) the model maintains the positivity property of the scalar concentration field, a physical realizability requirement for the simulation of scalars, when the proposed criterion is satisfied, (b) the model is such that the transport of the scalar concentration field is consistent with the transport of the volume fraction field, which prevents artificial numerical leakage of the scalar at the interface. Finally, we present numerical simulations using the proposed model in a wide range of two-phase flow regimes, spanning laminar to turbulent flows; and assess the accuracy and robustness of the model.

ISBN: 9798209784135Subjects--Topical Terms:

517751
Numerical analysis.

A Novel Diffuse-Interface Model and Numerical Methods for Compressible Turbulent Two-Phase Flows and Scalar Transport.
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100 1 $a Suresh, Suhas Jain. $3 3689347
245 1 0 $a A Novel Diffuse-Interface Model and Numerical Methods for Compressible Turbulent Two-Phase Flows and Scalar Transport.
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300 $a 180 p.
500 $a Source: Dissertations Abstracts International, Volume: 83-09, Section: B.
500 $a Advisor: Moin, Parviz;Lele, Sanjiva K. ;Mani, Ali;Lobo, Javier Urzary.
502 $a Thesis (Ph.D.)--Stanford University, 2021.
506 $a This item must not be sold to any third party vendors.
520 $a Compressible two-phase flows and the transport of scalars in two-phase flows have a wide range of applications in natural and engineering processes. In this thesis, we first propose a novel diuseinterface model for the simulation of compressible two-phase flows. We start with the baseline five-equation model that consists of equations for the transport of volume fraction, mass of each phase, momentum, and total energy. It is known that this model cannot be used with a nondissipative scheme as is, and the direct solution of these equations with a dissipative scheme results in artificial diusion of the interface, which results in poor accuracy. We therefore, propose adding interface-regularization (diusion-sharpening) terms to this five-equation model in such a way that the resulting model can now be used with a non-dissipative central scheme, and the model also maintains the discrete conservation of mass of each phase, momentum, and total energy of the system. We also show that the proposed interface-regularization terms in the model do not spuriously contribute to the total kinetic energy of the system and approximately satisfies the conservation of entropy, and therefore, do not aect the non-linear stability of the numerical simulation. However, it is also important to satisfy these conditions discretely.For a compressible flow, it is known that the discrete conservation of kinetic energy, in the absence of dissipative mechanisms, alone is not a sucient condition for numerical stability, unlike in incompressible flows. For stable numerical simulations of compressible flows, a discrete entropy condition needs to be satisfied. To achieve this, we first propose discrete consistency conditions between the numerical fluxes, and then present a set of numerical fluxes-which satisfies these consistency conditions-that results in an exact conservation of kinetic energy and approximate conservation of entropy (a KEEP scheme) in the absence of pressure work, viscosity, thermal di↵usion e↵ects, and time di↵erencing errors.As part of verification and validation, we present numerical simulations using the model and compare the results with the existing models in the literature to assess: (a) the accuracy of evolution of the interface shape, (b) the ability of the model to maintain constant interface thickness, (c) the ability to maintain conservation properties, (d) implementation of surface tension e↵ects, (e) propagation of acoustics and their interaction with material interfaces, (f) the accuracy and robustness of the numerical scheme for the simulation of high-Reynolds-number turbulent flows, and (g) performance and scalability of the method. We also present coarse-grid numerical simulations of compressible single-phase and two-phase turbulent flows at infinite Re, to illustrate the stability of the proposed method in canonical test cases, such as isotropic turbulence and Taylor-Green vortex flows. A resolved simulation of a droplet-laden isotropic turbulence is also presented at finite Re, and the e↵ect of the presence of droplets on the flow is analyzed.We also propose a novel scalar-transport model for the simulation of scalar quantities in two-phase flows. In a two-phase flow, the scalar quantities typically have disparate properties in two phases, which results in e↵ective confinement of the scalar quantities in one of the phases, in the time scales of interest. This confinement of the scalars lead to the formation of sharp gradients of the scalar concentration values at the interface, presenting a serious challenge for its numerical simulations. To overcome this challenge, we propose a new model for the transport of scalars in two-phase flows. The provable strengths of the proposed model are: (a) the model maintains the positivity property of the scalar concentration field, a physical realizability requirement for the simulation of scalars, when the proposed criterion is satisfied, (b) the model is such that the transport of the scalar concentration field is consistent with the transport of the volume fraction field, which prevents artificial numerical leakage of the scalar at the interface. Finally, we present numerical simulations using the proposed model in a wide range of two-phase flow regimes, spanning laminar to turbulent flows; and assess the accuracy and robustness of the model.
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