scholarly journals Effects of Wheel Rotation on Long-Period Wake Dynamics of the DrivAer Fastback Model

Fluids ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 19
Author(s):  
Matthew Aultman ◽  
Rodrigo Auza-Gutierrez ◽  
Kevin Disotell ◽  
Lian Duan
Keyword(s):  
Lattice Boltzmann Method ◽  
Motion Sickness ◽  
Vortex Shedding ◽  
Lattice Boltzmann ◽  
Low Frequency ◽  
Low Pressure ◽  
Side Force ◽  
Long Period ◽  
Total Vehicle ◽  
Boltzmann Method

Lattice Boltzmann method (LBM) simulations were performed to capture the long-period dynamics within the wake of a realistic DrivAer fastback model with stationary and rotating wheels. The simulations showed that the wake developed as a low-pressure torus regardless of whether the wheels were rotating. This torus shrank in size on the base in the case of rotating wheels, leading to a reduction in the low-pressure footprint on the base, and consequently a 7% decrease in the total vehicle drag in comparison to the stationary wheels case. Furthermore, the lateral vortex shedding experienced a long-period switching associated with the bi-stability in both the stationary and rotating wheels cases. This bi-stability contributed to low-frequency side force oscillations (<1 Hz) in alignment with the peak motion-sickness-inducing frequency (0.2 Hz).

FLOW EFFECT AROUND TWO SQUARE CYLINDERS ARRANGED SIDE BY SIDE USING LATTICE BOLTZMANN METHOD

2008 ◽  
Vol 19 (11) ◽  
pp. 1683-1694 ◽  
Author(s):  
YONG RAO ◽  
YUSHAN NI ◽  
CHAOFENG LIU
Keyword(s):  
Lattice Boltzmann Method ◽  
Vortex Shedding ◽  
Lattice Boltzmann ◽  
Reynolds Numbers ◽  
Small Space ◽  
Flip Flop ◽  
Drag And Lift Coefficients ◽  
Square Cylinders ◽  
Drag And Lift ◽  
Boltzmann Method

The flow around two square cylinders arranged side by side has been investigated through lattice Boltzmann method under different Reynolds numbers and various space ratios (s = d/D, d is the separation distance between two cylinders, D is the characteristic length) from 1.0, 1.1 to 2.7, including 18 space ratios. It is found that the flip-flop regime occurs at small space ratios and the synchronized regime occurs at large space ratios. Wide and narrow wakes at small spacing are formed and intermittently change behind the cylinders, and the biased flow in the gap is bistable. The frequency of vortex shedding is different in two wakes. The upper frequency is smaller than the lower frequency for small space ratios (s < 1.4), and the time-averaged drag and lift coefficients of cylinders are also different. When the space ratios increase, two distinct vortex streets occur behind the cylinders, and the frequency of vortex shedding is almost equal in two wakes. Also the difference of time-averaged drag and lift coefficients of the cylinders decreases with the increase in space ratios; in this case the flow shows synchronized regime. The transition between flip-flop and synchronized regimes occurs at s = 1.5. When s < 1.5, the flow shows flip-flop regime; otherwise, it shows synchronized regime. When s = 2.0 and 2.5, the curves for the time-averaged drag and lift coefficient with different Reynolds numbers are smooth. When s = 1.5 and 1.8, the curves are also smooth under Re ≤ 140, but that will be fluctuant under Re > 140 because of the nonlinear interaction between the wakes, and the instability of flow becomes stronger with the increase in Reynolds numbers. On the other hand, the vortex shedding type from the cylinder occurs in-phase when s < 2.5 and s = 2.5 for Re < 190, whereas that occurs anti-phase when s = 2.5 for Re ≥190. In addition, the pressure varies a little on the left surfaces and greatly on the right surfaces of both cylinders with the increase in Reynolds number at s = 2.5.

Simulation of Flow Around a Cube at Moderate Reynolds Numbers Using the Lattice Boltzmann Method

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Majid Hassan Khan ◽  
Atul Sharma ◽  
Amit Agrawal
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Lattice Boltzmann Method ◽  
Steady Flow ◽  
Flow Regime ◽  
Lattice Boltzmann ◽  
Reynolds Numbers ◽  
Side Force ◽  
Force Coefficients ◽  
Boltzmann Method

Abstract This article reports flow behavior around a suspended cube obtained using three-dimensional (3D) lattice Boltzmann method (LBM)-based simulations. The Reynolds number (Re) range covered is from 84 to 770. Four different flow regimes are noted based on the flow structure in this range of Re: steady axisymmetric (84 ≤ Re ≤ 200), steady nonaxisymmetric (215 ≤ Re ≤ 250), unsteady nonaxisymmetric in one plane and axisymmetric in the other plane (276 ≤ Re ≤ 300), and unsteady nonaxisymmetric in streamwise orthogonal planes (339 ≤ Re ≤ 770). Recirculation length and drag coefficient follow inverse trend in the steady flow regime. The unsteady flow regime shows hairpin vortices for Re ≤ 300 and then it becomes structureless. The nature of force coefficients has been examined at various Reynolds numbers. Temporal behavior of force coefficients is presented along with phase dependence of side force coefficients. The drag coefficient decreases with increase in Reynolds number in the steady flow regime and the side force coefficients are in phase. Drag coefficients are compared with established correlations for flow around a cube and a sphere. The side force coefficients are perfectly correlated at Re = 215 and they are anticorrelated at Re = 250. At higher Reynolds numbers, side force coefficients are highly uncorrelated. This work adds to the existing understanding of flow around a cube reported earlier at low and moderate Re and extends it further to unsteady regime at higher Re.

Lattice Boltzmann method for adiabatic acoustics

2011 ◽  
Vol 369 (1944) ◽  
pp. 2371-2380 ◽  
Author(s):  
Yanbing Li ◽  
Xiaowen Shan
Keyword(s):  
Fluid Dynamics ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Collision Frequency ◽  
Low Frequency ◽  
Navier Stokes ◽  
Sound Waves ◽  
Frequency Limit ◽  
Molecular Collision ◽  
Boltzmann Method

The lattice Boltzmann method (LBM) has been proved to be a useful tool in many areas of computational fluid dynamics, including computational aero-acoustics (CAA). However, for historical reasons, its applications in CAA have been largely restricted to simulations of isothermal (Newtonian) sound waves. As the recent kinetic theory-based reformulation establishes a theoretical framework in which LBM can be extended to recover the full Navier–Stokes–Fourier (NS) equations and beyond, in this paper, we show that, at least at the low-frequency limit (sound frequency much less than molecular collision frequency), adiabatic sound waves can be accurately simulated by the LBM provided that the lattice and the distribution function ensure adequate recovery of the full NS equations.

Aeroacoustic Simulations Using Compressible Lattice Boltzmann Method

2016 ◽  
Vol 8 (5) ◽  
pp. 795-809 ◽  
Author(s):  
Kai Li ◽  
Chengwen Zhong
Keyword(s):  
Numerical Simulation ◽  
Lattice Boltzmann Method ◽  
Vortex Shedding ◽  
Lattice Boltzmann ◽  
Buffer Zone ◽  
Computational Domain ◽  
Absorbing Boundary ◽  
Naca0012 Airfoil ◽  
Characteristic Features ◽  
Boltzmann Method

AbstractThis paper presents a lattice Boltzmann (LB) method based study aimed at numerical simulation of aeroacoustic phenomenon in flows around a symmetric obstacle. To simulate the compressible flow accurately, a potential energy double-distribution-function (DDF) lattice Boltzmann method is used over the entire computational domain from the near to far fields. The buffer zone and absorbing boundary condition is employed to eliminate the non-physical reflecting. Through the direct numerical simulation, the flow around a circular cylinder atRe=150,M=0.2 and the flow around a NACA0012 airfoil atRe=10000,M=0.8,α=0° are investigated. The generation and propagation of the sound produced by the vortex shedding are reappeared clearly. The obtained results increase our understanding of the characteristic features of the aeroacoustic sound.

scholarly journals Numerical Simulation of Drag Reduction on a Square Rod Detached with Two Control Rods at Various Gap Spacing via Lattice Boltzmann Method

Symmetry ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 475 ◽  
Author(s):  
Raheela Manzoor ◽  
Asma Khalid ◽  
Ilyas Khan ◽  
Shams-Ul-Islam ◽  
Dumitru Baleanu ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Lattice Boltzmann Method ◽  
Vortex Shedding ◽  
Lattice Boltzmann ◽  
Flow Mode ◽  
Percentage Reduction ◽  
Spacing Ratio ◽  
Boltzmann Method ◽  
Gap Spacing ◽  
Control Rods

Numerical simulations are performed to examine the effect of size of control rods (d1) and spacing ratio (g) on flow around a square rod with upstream and downstream control rods aligned in-line using the lattice Boltzmann method (LBM). The Reynolds number (Re) is fixed at Re = 160, while the spacing between the main rod and control rods is taken in the range 1 ≤ g ≤ 5 and the size of the control rod is varied between 4 and 20. Seven different types of flow mods are observed in this study at different values of g and d1. Variation in force statistics, like mean drag coefficient (Cdmean), Strouhal number (St), root mean square values of drag (Cdrms) and lift coefficients (Clrms), and percentage reduction in mean drag coefficient is discussed in detail. It was examined that vortex shedding completely suppressed at (g, d1) = (1, 12), (2, 12), and (2, 16) where steady flow mode exists. Moreover, it was found that at large gap spacing, where g = 5, the effect of control rods on the main rod vanishes. Due to this strong vortex shedding produced and as a result, maximum value of Cdmean is found at (g, d1) = (5, 8). The negative values of mean drag force are also observed at some gap spacing and size of control rods are due to the effect of thrust. Furthermore, the maximum percentage reduction in Cdmean is 121%, found at (g, d1) = (2, 20).

Flow Behaviour Around Square and Circular Obstacles in 2D and 3D Configurations Using Lattice Boltzmann Method

2014 ◽  
Author(s):  
Wafik Abassi ◽  
Fethi Aloui ◽  
Sassi Ben Nasrallah ◽  
Laurent Keirsbulck ◽  
Jack Legrand
Keyword(s):  
Lattice Boltzmann Method ◽  
Cross Section ◽  
Vortex Shedding ◽  
Lattice Boltzmann ◽  
Flow Behavior ◽  
Circular Cross Section ◽  
Practical Interest ◽  
Maximum Velocity ◽  
Boltzmann Method ◽  
2D And 3D

The investigation of wakes of bluff bodies in a channel is still relevant despite the large number of works devoted on it, in both experimental and numerical studies. This attractiveness is mainly due to its related applications and practical interest in varied engineering fields. The understanding of dynamic flow behavior and the topology of the instability structures occurring in the wake is essential in order to optimize the obstacle shape according to the desired objectives. A confined laminar flow around a square and a circle, placed in a channel is numerically investigated in this work using Lattice Boltzmann method. The study is then extended to 3D computations with horizontal cylinder within a square then a circular cross-section mounted inside a rectangular duct. The Reynolds number (Re), based on the maximum velocity and the cross-section height varies between 50 and 120 and the blockage ratio is r=1/3. This geometry is representative of a passive method to enhance mixing in the laminar channel flow. LBM was built up on the D2Q9 and D3Q19 model for respectively 2D and 3D computations. The single relaxation time approach called the lattice-BGK method was adopted. The topology of the vortex-shedding phenomena and wake behavior according the Reynolds numbers, for both geometries of the obstacle are focused. The effect of wall confinement on the flow transition to the vortex shedding regime is discussed. Velocity profiles and integral parameters such as recirculation length and Strouhal number were investigated. The numerical results are supported by literatures works results for the same configuration showing the performance of LBM as numerical tools simulation for such kind of flows.

Numerical Study on Cross-Flow around Three Cylinders Using Lattice Boltzmann Method

2014 ◽  
Vol 525 ◽  
pp. 311-315
Author(s):  
Xiang Cui Lv ◽  
Wei Zhang ◽  
Dian Xin Zhang
Keyword(s):  
Reynolds Number ◽  
Lattice Boltzmann Method ◽  
Vortex Shedding ◽  
Lattice Boltzmann ◽  
Numerical Study ◽  
Cross Flow ◽  
Evolution Process ◽  
Spacing Ratio ◽  
The Right ◽  
Boltzmann Method

The flow around three cylinders in isosceles left-triangle and right-triangle configurations at Reynolds number of 200 are investigated using lattice Boltzmann method (LBM). Vortex shedding pattern and evolution process in the wake of each cylinder in the two cases are analyzed with a spacing ratio of 4. Results show that the flow pattern in the right-triangle configuration is symmetrical and the vortex shedding is anti-phase. Meanwhile, vortex shedding in-phase is observed in the left-triangle configuration which is due to the effect of the periodical vortex shedding behind upstream cylinder. The evolution process of vortex in the wakes of the cylinders for left-triangle configuration is simulated numerically.

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