Numerical Simulation of Drag Reduction in Microgrooved Substrates Using Lattice-Boltzmann Method

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
H. Asadzadeh ◽  
A. Moosavi ◽  
A. Etemadi
Keyword(s):  
Drag Reduction ◽  
Drag Coefficient ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Groove Depth ◽  
Friction Drag ◽  
Total Drag ◽  
Pressure Drag ◽  
Depth Ratio ◽  
Boltzmann Method

We study drag reduction of a uniform flow over a flat surface due to a series of rectangular microgrooves created on the surface. The results reveal that making grooves on the surface usually leads to the generation of secondary vortices inside the grooves that, in turn, decreases the friction drag force and increases the pressure drag force. By increasing the thickness of the grooves to the thickness of the obstacle, the pressure drag increases due to the enhancement of the generated vortices and the occurrence of separation phenomenon and the friction drag reduces due to a decrease of the velocity gradient on the surface. In addition, by increasing the grooves depth ratio, the pressure drag coefficient decreases and the friction drag coefficient increases. However, the impact of the pressure drag coefficient is higher than that of the friction drag coefficient. From a specific point, increasing the groove depth ratio does not effect on decreasing the total pressure drag of the plate. Therefore, creating the grooves in flat surfaces would reduce the total drag coefficient of the plate if the thickness of the grooves does not exceed a specific size and the depth of the grooves is chosen to be sufficiently large. The lattice-Boltzmann method (LBM) is used and the optimal reduction of the drag coefficient is calculated. It is found that for the width ratio equal to 0.19 and the groove depth ratio equal to 0.2548, about 7% decrease is achieved for the average total drag.

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.

Research on the mechanism of drag reduction by wall vibration through Lattice Boltzmann method

2020 ◽  
Vol 34 (27) ◽  
pp. 2050295
Author(s):  
Jia Zhen Zhao ◽  
Guang Pan ◽  
Shan Gao
Keyword(s):  
Drag Reduction ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Normal Vibration ◽  
Liquid Interface ◽  
Geometry Model ◽  
Vibration Parameters ◽  
Solid Liquid Interface ◽  
Boltzmann Method ◽  
Solid Liquid

In this paper, the hydrodynamics of streamwise and normal vibration wall are studied using the Lattice Boltzmann method. Firstly, based on the two-dimensional flow geometry model, which is made up of flat wall and water fluid, the characters of the fluid near the streamwise and normal vibration wall are simulated under the condition of mutative vibration parameters. By rigorous data treating, some notable results such as the velocity distribution, density distribution curves of the flow field, and the frictional force of the solid-liquid interface are gained. Secondly, the reason of the change of frictional resistance at the solid-liquid interface by wall vibration are studied. And the results are evidence that well drag reduction effect can be obtained by applying appropriate flow vibration parameters to the solid wall. In addition, the reduction in fluid density near the solid-liquid wall is another significant cause behind the frictional drag decrease.

Drag reduction in a channel with microstructure grooves using the lattice Boltzmann method

2017 ◽  
Vol 50 (10) ◽  
pp. 105301 ◽  
Author(s):  
M A Daeian ◽  
A Moosavi ◽  
A Nouri-Borujerdi ◽  
E Taghvaei
Keyword(s):  
Drag Reduction ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Boltzmann Method

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).

Landing Gear Drag Reduction Using Lattice Boltzmann Method

2018 ◽  
Author(s):  
Pedro H. Caruy Povoa ◽  
Rodrigo M. Granzoto ◽  
Gilberto G. Becker ◽  
Mauro R. Lopez
Keyword(s):  
Drag Reduction ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Landing Gear ◽  
Boltzmann Method
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