scholarly journals Volumetric Lattice Boltzmann Method for Wall Stresses of Image-based Pulsatile Flows

2021 ◽  
Author(s):  
Xiaoyu Zhang ◽  
Joan Gomez-Paz ◽  
J. M. McDonough ◽  
Mahfuzul MD Is ◽  
Yiannis Andreopoulos ◽  
...  
Keyword(s):  
Lattice Boltzmann Method ◽  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Laminar Flows ◽  
Strain Rate Tensor ◽  
Pulsatile Flows ◽  
A New Technique ◽  
Seamless Connection ◽  
Boltzmann Method ◽  
Computational Platform

Abstract Image-based computational fluid dynamics (CFD) has become a new capability for determining wall stresses of pulsatile flows. However, a computational platform that directly connects image information to pulsatile wall stresses is lacking. Prevailing methods rely on manual crafting of a hodgepodge of multidisciplinary software packages, which is usually laborious and error prone. We present a new technique to compute wall stresses in image-based pulsatile flows using the lattice Boltzmann method (LBM). The novelty includes: (1) a unique image processing to extract flow domain and local wall normality, (2) a seamless connection between image extraction and CFD, (3) an en-route calculation of strain-rate tensor, and (4) GPU acceleration (not included here). We first generalize the streaming operation in the LBM and then conduct an application study for laminar and turbulent pulsatile flows in an image-based pipe (Reynolds number: 10 to 5000). The computed pulsatile velocity and shear stress are in good agreement with Womersley solutions for laminar flows and concurrent laboratory measurements for turbulent flows. This technique is being used to study (1) the hemodynamic wall stresses in inner choroid endothelium, (2) the drag force in sand flows, and (3) effects of waste streams on ion exchange kinetics in porous media.

Lattice Boltzmann method for axisymmetric turbulent flows

2015 ◽  
Vol 26 (09) ◽  
pp. 1550099 ◽  
Author(s):  
Wei Wang ◽  
Jian Guo Zhou
Keyword(s):  
Lattice Boltzmann Method ◽  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Lattice Gas ◽  
Numerical Solutions ◽  
Lattice Boltzmann Model ◽  
Consistent Manner ◽  
Pulsatile Flows ◽  
Separated And Reattached Flow ◽  
Boltzmann Method

A lattice Boltzmann model for axisymmetric turbulent flows is developed. It is a further development of the enhanced axisymmetric lattice Boltzmann method (AxLAB®). The turbulent flow is efficiently and naturally simulated through incorporation of the standard subgrid-scale (SGS) stress model into the axisymmetric lattice Boltzmann equation in a consistent manner with the lattice gas dynamics. The model is verified by applying it to three typical cases in engineering: (i) pipe flow through an abrupt axisymmetric constriction, (ii) axisymmetric separated and reattached flow and (iii) pulsatile flows in a stenotic vessel. The numerical results obtained using the present method are compared with experimental data and other available numerical solutions, indicating good agreements. The model is simple and is able to predict axisymmetric turbulent flows at good accuracy.

Direct Transmission Loss Calculation of Simplified Muffler Configurations Using a Lattice-Boltzmann Method

2013 ◽  
Author(s):  
Adrien Mann ◽  
Franck Pérot
Keyword(s):  
Lattice Boltzmann Method ◽  
Turbulent Flows ◽  
Spatial Resolution ◽  
Lattice Boltzmann ◽  
Transmission Loss ◽  
Fan Noise ◽  
Wind Noise ◽  
Simulation Domain ◽  
Flow Induced Noise ◽  
Boltzmann Method

Lattice-Boltzmann Method (LBM) is broadly used for the simulation of aeroacoustics problems. This time-domain CFD/CAA approach is transient, explicit and compressible and offers an accurate and efficient solution to simultaneously resolve turbulent flows and their corresponding flow-induced noise radiation. Some examples of applications are ground transportation wind-noise problems, buffeting, Heating, Ventilation, and Air Conditioning (HVAC), fan noise, etc. As shown in previous studies, LBM can also be used to accurately handle linear acoustics problems if the source of noise is not a flow but a simple acoustic source. This set of capabilities makes LBM a suitable candidate for evaluating the acoustics performances of exhaust systems and mufflers. Compared to other traditional acoustics methods, LBM presents the advantage to skip tedious volume meshing operations since the mesh generation is fully automatic. Furthermore, considering that all geometrical details are included in the simulation domain and that LBM is explicit, high frequencies mechanisms up to 10–20 kHz can be captured. The upper frequency limit is indeed solely driven by the spatial resolution used to discretize the system. In this paper, three academic 3-D geometries representative of production muffler systems are studied. Transmission Loss (TL) measurements are performed on three configurations and these experiments are reproduced numerically with LBM. The experimental setup is described in a first part and the numerical details are given in a second part and third part. In particular, the method used to calculate the TL in the simulation and the convergence of the results with respect to the spatial resolution are shown. In a third part, the simulations are compared to the TL measurements and a numerical investigation of the effect of geometry details on the simulated results is proposed. This study highlights the sensitivity of acoustics measurements to geometry details.

Numerical Investigation of Flow Over an Airfoil by the Lattice Boltzmann Method

2013 ◽  
Author(s):  
Felipe A. Valenzuela ◽  
Amador M. Guzmán ◽  
Andrés J. Díaz
Keyword(s):  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Preliminary Investigation ◽  
Computational Cost ◽  
Fluid Flows ◽  
Laminar Flows ◽  
Navier Stokes ◽  
Laminar Separation ◽  
Refinement Method ◽  
Boltzmann Method

During the last years the aerodynamics characteristics of airfoils have been studied solving numerically the Navier-Stokes (NS) equations. These calculations require a significant computational cost due to both the second order and the nonlinear characteristics of the NS partial differential equations. Therefore, efforts have been devoted to reduce this cost and increase the accuracy of the numerical methods. The Lattice-Boltzmann Method (LBM) has become a great alternative to simulate this problem and a variety of fluid flows. In this method, the convective operator is linear and the pressure is calculated directly by the equation of state without implementing iterative methods. This work represents a preliminary investigation of a laminar flow over airfoils under low Reynolds number conditions (Re = 500). Solutions are obtained using a Multi-Block mesh refinement method. In order to validate the computational code, calculations are performed on a SD7003 airfoil at an angle of attack of 4° and 30°, which corresponds to the available numerical and experimental results. The results of this study agree well with previous experimental and numerical studies demonstrating the capabilities of the LBM to simulate accurately laminar flows over airfoils as well as capturing and predicting the laminar separation bubbles.

Consistent subgrid scale modelling for lattice Boltzmann methods

2012 ◽  
Vol 700 ◽  
pp. 514-542 ◽  
Author(s):  
Orestis Malaspinas ◽  
Pierre Sagaut
Keyword(s):  
Lattice Boltzmann Method ◽  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Stokes Equations ◽  
Mixing Layer ◽  
Velocity Distribution Function ◽  
Theoretical Point ◽  
Subgrid Scale ◽  
Hermite Expansion ◽  
Boltzmann Method

AbstractThe lattice Boltzmann method has become a widely used tool for the numerical simulation of fluid flows and in particular of turbulent flows. In this frame the inclusion of subgrid scale closures is of crucial importance and is not completely understood from the theoretical point of view. Here, we propose a consistent way of introducing subgrid closures in the BGK Boltzmann equation for large eddy simulations of turbulent flows. Based on the Hermite expansion of the velocity distribution function, we construct a hierarchy of subgrid scale terms, which are similar to those obtained for the Navier–Stokes equations, and discuss their inclusion in the lattice Boltzmann method scheme. A link between our approach and the standard way on including eddy viscosity models in the lattice Boltzmann method is established. It is shown that the use of a single modified scalar relaxation time to account for subgrid viscosity effects is not consistent in the compressible case. Finally, we validate the approach in the weakly compressible case by simulating the time developing mixing layer and comparing with experimental results and direct numerical simulations.

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