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Direct Numerical Simulation and a New 3-D Discrete Dynamical System for Image-based Complex Flows Using Volumetric Lattice Boltzmann Method /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Direct Numerical Simulation and a New 3-D Discrete Dynamical System for Image-based Complex Flows Using Volumetric Lattice Boltzmann Method // Xiaoyu Zhang.
Author:	Zhang, Xiaoyu,
Description:	1 electronic resource (112 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 86-04, Section: B.
Contained By:	Dissertations Abstracts International86-04B.
Subject:	Carotid arteries. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31345253
ISBN:	9798342105620

Direct Numerical Simulation and a New 3-D Discrete Dynamical System for Image-based Complex Flows Using Volumetric Lattice Boltzmann Method /
Zhang, Xiaoyu,

Direct Numerical Simulation and a New 3-D Discrete Dynamical System for Image-based Complex Flows Using Volumetric Lattice Boltzmann Method /Xiaoyu Zhang. - 1 electronic resource (112 pages)

Source: Dissertations Abstracts International, Volume: 86-04, Section: B.

The kinetic-based lattice Boltzmann method (LBM) is a specialized computational fluid dynamics (CFD) technique that resolves intricate flow phenomena at the mesoscale level. The LBM is particularly suited for large-scale parallel computing on Graphic Processing Units (GPU) and simulating multi-phase flows. By incorporating a volume fraction parameter, LBM becomes a volumetric lattice Boltzmann method (VLBM), leading to advantages such as easy handling of complex geometries with/without movement. These capabilities render VLBM an effective tool for modeling various complex flows. In this study, we investigated the computational modeling of complex flows using VLBM, focusing particularly on pulsatile flows, the transition to turbulent flows, and pore-scale porous media flows. Furthermore, a new discrete dynamical system (DDS) is derived and validated for potential integration into large eddy simulations (LES) aimed at enhancing modeling for turbulent and pulsatile flows.Pulsatile flows are prevalent in nature, engineering, and the human body. Understanding these flows is crucial in research areas such as biomedical engineering and cardiovascular studies. However, the characteristics of oscillatory, variability in Reynolds number (Re), and shear stress bring difficulties in the numerical modeling of pulsatile flows. To analyze and understand the shear stress variability in pulsatile flows, we first developed a unique computational method using VLBM to quantify four-dimensional (4-D) wall stresses in image-based pulsatile flows. The method is validated against analytical solutions and experimental data, showing good agreement. Additionally, an application study is presented for the non-invasive quantification of 4-D hemodynamics in human carotid and vertebral arteries.Secondly, the transition to turbulent flows is studied as it plays an important role in the understanding of pulsatile flows since the flow can shift from laminar to transient and then to turbulent within a single flow cycle. We conducted direct numerical simulations (DNS) using VLBM in a three-dimensional (3-D) pipe and investigated the flow at Re ranging from 226 to 14066 in the Lagrangian description. Results demonstrate good agreement with analytical solutions for laminar flows and with open data for turbulent flows. Key observations include the disappearance of parabolic velocity profiles when Re>2300, the fluctuation of turbulent kinetic energy (TKE) between laminar and turbulent states within the range 2300< \uD835\uDC45\uD835\uDC52<4000, and notably the tendency for skewness \uD835\uDC46 to stabilize a constant value of -0.53 as Tayler microscale Reynolds number \uD835\uDC45\uD835\uDC52\uD835\uDF06 approaches 103.Thirdly, to develop an appropriate sub-grid scale (SGS) model for LES modeling of pulsatile flows, a new 3-D DDS is derived from volumetric lattice Boltzmann equations (VLBE) using a Galerkin procedure. The DDS is characterized by two bifurcation parameters: splitting factor β and rescaling factor θ. Its capability to capture multiple flow behaviors, including but not limited to noisy n-period with different fundamental, noisy subharmonic n-period, noisy quasiperiodic, and broadband, is validated through numerical experiments. The optimal range for these bifurcation parameters is determined to be 0.641226<\uD835\uDEFD<0.816106 and 1.243186<\uD835\uDF03<1.430332 by a numerical test. Comparison of DDS results from the identified bifurcation parameter range with DNS data, particularly in terms of time series features, confirmed the validity of DDS. These results suggest its potential applicability in LES for predicting SGS physics, applicable to both pulsatile flows and turbulence modeling.Additionally, we expanded the current VLBM from advection to include diffusionadvection and conducted simulations for another type of complex flow, i.e., porous media flows at pore-scale, with a focus on the transport of nuclear waste isotopes in geopolymer porous structures. Rigorous validation against the finite difference method (FDM) for velocity fields and the phase field method (PFM) for concentration fields confirms the accuracy of the VLBM model. Systematic investigations reveal the influence of key parameters such as inlet velocity, isotope diffusivity, and porosity of porous structure on the diffusion-advection process. Increasing the background flow and diffusivity significantly accelerated the process. Conversely, an increase in porosity had a less pronounced effect, a slight slowdown of the diffusion-advection process due to the expanded pore volume.

English

ISBN: 9798342105620Subjects--Topical Terms:

3821618
Carotid arteries.

Direct Numerical Simulation and a New 3-D Discrete Dynamical System for Image-based Complex Flows Using Volumetric Lattice Boltzmann Method /
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520 $a The kinetic-based lattice Boltzmann method (LBM) is a specialized computational fluid dynamics (CFD) technique that resolves intricate flow phenomena at the mesoscale level. The LBM is particularly suited for large-scale parallel computing on Graphic Processing Units (GPU) and simulating multi-phase flows. By incorporating a volume fraction parameter, LBM becomes a volumetric lattice Boltzmann method (VLBM), leading to advantages such as easy handling of complex geometries with/without movement. These capabilities render VLBM an effective tool for modeling various complex flows. In this study, we investigated the computational modeling of complex flows using VLBM, focusing particularly on pulsatile flows, the transition to turbulent flows, and pore-scale porous media flows. Furthermore, a new discrete dynamical system (DDS) is derived and validated for potential integration into large eddy simulations (LES) aimed at enhancing modeling for turbulent and pulsatile flows.Pulsatile flows are prevalent in nature, engineering, and the human body. Understanding these flows is crucial in research areas such as biomedical engineering and cardiovascular studies. However, the characteristics of oscillatory, variability in Reynolds number (Re), and shear stress bring difficulties in the numerical modeling of pulsatile flows. To analyze and understand the shear stress variability in pulsatile flows, we first developed a unique computational method using VLBM to quantify four-dimensional (4-D) wall stresses in image-based pulsatile flows. The method is validated against analytical solutions and experimental data, showing good agreement. Additionally, an application study is presented for the non-invasive quantification of 4-D hemodynamics in human carotid and vertebral arteries.Secondly, the transition to turbulent flows is studied as it plays an important role in the understanding of pulsatile flows since the flow can shift from laminar to transient and then to turbulent within a single flow cycle. We conducted direct numerical simulations (DNS) using VLBM in a three-dimensional (3-D) pipe and investigated the flow at Re ranging from 226 to 14066 in the Lagrangian description. Results demonstrate good agreement with analytical solutions for laminar flows and with open data for turbulent flows. Key observations include the disappearance of parabolic velocity profiles when Re>2300, the fluctuation of turbulent kinetic energy (TKE) between laminar and turbulent states within the range 2300< \uD835\uDC45\uD835\uDC52<4000, and notably the tendency for skewness \uD835\uDC46 to stabilize a constant value of -0.53 as Tayler microscale Reynolds number \uD835\uDC45\uD835\uDC52\uD835\uDF06 approaches 103.Thirdly, to develop an appropriate sub-grid scale (SGS) model for LES modeling of pulsatile flows, a new 3-D DDS is derived from volumetric lattice Boltzmann equations (VLBE) using a Galerkin procedure. The DDS is characterized by two bifurcation parameters: splitting factor β and rescaling factor θ. Its capability to capture multiple flow behaviors, including but not limited to noisy n-period with different fundamental, noisy subharmonic n-period, noisy quasiperiodic, and broadband, is validated through numerical experiments. The optimal range for these bifurcation parameters is determined to be 0.641226<\uD835\uDEFD<0.816106 and 1.243186<\uD835\uDF03<1.430332 by a numerical test. Comparison of DDS results from the identified bifurcation parameter range with DNS data, particularly in terms of time series features, confirmed the validity of DDS. These results suggest its potential applicability in LES for predicting SGS physics, applicable to both pulsatile flows and turbulence modeling.Additionally, we expanded the current VLBM from advection to include diffusionadvection and conducted simulations for another type of complex flow, i.e., porous media flows at pore-scale, with a focus on the transport of nuclear waste isotopes in geopolymer porous structures. Rigorous validation against the finite difference method (FDM) for velocity fields and the phase field method (PFM) for concentration fields confirms the accuracy of the VLBM model. Systematic investigations reveal the influence of key parameters such as inlet velocity, isotope diffusivity, and porosity of porous structure on the diffusion-advection process. Increasing the background flow and diffusivity significantly accelerated the process. Conversely, an increase in porosity had a less pronounced effect, a slight slowdown of the diffusion-advection process due to the expanded pore volume.
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650 4 $a Partial differential equations. $3 2180177
650 4 $a Viscosity. $3 1050706
650 4 $a Isotopes. $3 664463
650 4 $a Veins & arteries. $3 3681939
650 4 $a Design. $3 518875
650 4 $a Reynolds number. $3 3681436
650 4 $a Shear stress. $3 3681838
650 4 $a Fluid mechanics. $3 528155
650 4 $a Mathematics. $3 515831
650 4 $a Petroleum engineering. $3 566616
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