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).

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.

Numerical Simulation of Cross-Flow around Four Cylinders in a Square Configuration Using Lattice Boltzmann Method

2013 ◽  
Vol 405-408 ◽  
pp. 3259-3262 ◽  
Author(s):  
Wei Zhang ◽  
Hui Hua Ye ◽  
Jian Hua Tao
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Lattice Boltzmann Method ◽  
Vortex Shedding ◽  
Lattice Boltzmann ◽  
Cross Flow ◽  
Spacing Ratio ◽  
Square Configuration ◽  
Boltzmann Method ◽  
Four Cylinders

The flow around four cylinders in a square configuration with a spacing ratio 4 and Reynolds number of 200 are investigated using lattice Boltzmann method for angles of incidence α=0 and 45º, respectively. The results show that no biased flow occurs and the flow pattern is symmetrical at α=0, and the vortex shedding exists after the upstream cylinders which is completely different from the experimental results. It is hard to explain the discrepancy at present. The phenomenon of vortex shedding in-phase observed in the experiment reappears in the numerical simulation at α=45º.

Numerical Simulation for Flow over Two Circular Cylinders in Micro Channel with Lattice Boltzmann Method

2014 ◽  
Vol 670-671 ◽  
pp. 747-750
Author(s):  
Zhi Jun Gong ◽  
Jiao Yang ◽  
Wen Fei Wu
Keyword(s):  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Recirculation Zone ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Micro Channel ◽  
Zone Length ◽  
Spacing Ratio ◽  
Boltzmann Method

For indepth study on flow characteristics for fluid bypass obstacles in micro-channel, the Lattice Boltzmann Method (LBM) was used to simulate fluid flow over two circular cylinders in side-by-side arrangement of a micro-channel. The velocity distribution and recirculation zone length under different Reynolds numbers (Re = 0~100) and different spacing ratio (H/D= 0~2.0) were obtained. The results show that the pattern of flow and the size of recirculation zone in the micro-channel depend on the combined effect of Re and H/D.

Numerical simulation of flow over a square cylinder with upstream and downstream circular bar using lattice Boltzmann method

2018 ◽  
Vol 29 (04) ◽  
pp. 1850030 ◽  
Author(s):  
Yuan Ma ◽  
Rasul Mohebbi ◽  
M. M. Rashidi ◽  
Zhigang Yang
Keyword(s):  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Flow Patterns ◽  
Percentage Reduction ◽  
Square Cylinder ◽  
Distance Ratio ◽  
Maximum Percentage ◽  
Circular Bar ◽  
Boltzmann Method ◽  
Downstream Control

A numerical investigation is carried out to analyze the flow patterns, drag and lift coefficients, and vortex shedding around a square cylinder using a control circular bar upstream and downstream. Lattice Boltzmann method (LBM) was used to investigate flow over a square cylinder controlled by upstream and downstream circular bar, which is the main novelty of this study. Compared with those available results in the literature, the code for flow over a single square cylinder proves valid. The Reynolds number (Re) based on the width of the square cylinder ([Formula: see text]) and diameter of circular bar ([Formula: see text]) are 100 for square cylinder, 30 and 50 for different circular bars. Numerical simulations are performed in the ranges of [Formula: see text] and [Formula: see text], where [Formula: see text] and [Formula: see text] are the center-to-center distances between the bar and cylinder. Five distinct flow patterns are observed in the present study. It is found that the maximum percentage reduction in drag coefficient is 59.86% by upstream control bar, and the maximum percentage reduction in r.m.s. lift coefficient is 73.69% by downstream control bar. By varying the distance ratio for the downstream control bar, a critical value of distance ratio is found where there are two domain frequencies.

Numerical acoustic simulation of flow around circular cylinders based on Lattice Boltzmann method and Ffowcs Williams-Hawkings acoustic equation

2018 ◽  
Vol 07 (01n02) ◽  
pp. 1850010
Author(s):  
H. R. Hu ◽  
C. Zhang ◽  
X. Wang
Keyword(s):  
Lattice Boltzmann Method ◽  
Sound Pressure Level ◽  
Lattice Boltzmann ◽  
Sound Pressure ◽  
Vertical Direction ◽  
Pressure Level ◽  
Circular Cylinders ◽  
Acoustic Equation ◽  
Spacing Ratio ◽  
Boltzmann Method

Based on the GPU acceleration technique, Lattice Boltzmann method (LBM) and Ffowcs Williams-Hawkings (FW-H) acoustic equation are adopted to simulate the noise generated by flow around fixed and rotating circular cylinders when Reynolds number (Re) is 200. The results show that the sound pressure level has a peak in the vertical direction and it is higher than that in the streamwise direction. The maximum sound pressure level is significantly reduced when the cylinder rotates due to the suppression of vortex shedding compared to the case of a fixed cylinder. For tandem cylinders, the maximum sound pressure level in the vertical direction increases as the spacing ratio increases, and for parallel cylinders, it decreases as the spacing ratio increases. In addition, when using graphic processing unit (GPU), the computational efficiency is improved greatly and the speed-up reaches nearly 100.

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.

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).

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.

Numerical simulation of natural convection in a porous cavity with internal hot and cold sources by lattice Boltzmann method

2021 ◽  
Author(s):  
Ying Zhang ◽  
Xuhui Huang ◽  
Yichen Huang ◽  
Meng Xu ◽  
Jie Lei
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Exchange ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Heat Transfer Performance ◽  
Size Ratio ◽  
Transfer Performance ◽  
Spacing Ratio ◽  
Boltzmann Method

Based on the non-orthogonal multiple-relaxation time lattice Boltzmann method (MRT-LBM), natural convection in a porous square cavity with a pair of isothermally hot and cold blocks inside has been studied numerically in the current study. The influence of arrangements (Case1, Case2, Case3, Case4, Case5), spacing ratio (S) and size ratio (A) of the hot and cold sources and the Rayleigh number (Ra) on the heat exchange efficiency has been studied. The results show that different arrangements produce different heat transfer effects. Hot and cold blocks placed horizontally (Case1) and hot block located in the upper left corner while cold block located in the bottom right corner (Case4) have better heat exchange performances than other three cases since the flow directions of hot and cold fluids are closer to that of heat transfer. Then the influence of spacing between blocks and size of blocks on heat transfer rate is further studied in Case1 and Case4. The heat transfer performance is improved with A increasing. Additionally, the variation of heat transfer performance with spacing is related to the arrangement and size ratio of blocks. For Ra=104, 105 and 106, the best heat transfer characteristic can be obtained in Case1 when S=0.05 and A=0.20. For Ra=107, Case4 exhibits the best heat transfer effect when S=0.35 and A=0.20.

A Lattice Boltzmann Simulation of Cross-Flow Around Four Cylinders in a Square Arrangement

2010 ◽  
Author(s):  
J. Abolfazli Esfahani ◽  
A. R. Vasel Be Hagh
Keyword(s):  
Reynolds Number ◽  
Lattice Boltzmann Method ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Lattice Boltzmann ◽  
Cross Flow ◽  
Spacing Ratio ◽  
Volume Method ◽  
Boltzmann Method ◽  
Four Cylinders

The purpose of the present work is simulating cross flow around four cylinders in a square configuration by using a Lattice Boltzmann method. The effective parameters such as Reynolds number and spacing ratio L/D are chosen on the basis of former researches of other authors which have been done experimentally or by using traditional numerical schemes like finite volume method to provide the opportunity for comparing Lattice Boltzmann results with those obtained from experimental and CFD studies. Hence, the Reynolds number is set at Re = 100 and the spacing ratio is chosen to be 1.5, 2.5, 3.5, 4.5. It is shown that final results such as flow pattern, velocity and vorticity field are in accordance with those obtained by former researchers via experimental efforts or by use of finite volume method. This good agreement beside other important qualities such as efficient code, not having mesh tangling associated with other common numerical approaches, high convergence speed and nondimensional velocity and pressure field indicate this fact that in comparison with other numerical methods, Lattice Boltzmann method is very capable of analyzing a broad variety of fluid flows.

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