Numerical simulation of flow past rectangular cylinders with different aspect ratios using the incompressible lattice Boltzmann method

Abstract

This paper presents a numerical study of a uniform flow past a rectangular cylinder using the incompressible lattice Boltzmann method (ILBM). Firstly, we use the ILBM to simulate the flow past a square cylinder symmetrically placed in a two-dimensional channel and results are validated against the well-resolved results obtained using finite-difference method and finite-volume method. Secondly, the effects of the aspect ratio defined as R = width/height on the fluid forces, vortex shedding frequency and the flow structures in the wake are investigated. Aspect ratios ranging from 0.15 to 4.00 and four Reynolds numbers Re = 100, 150, 200 and 250 are selected for the investigation. The results show that the effects of aspect ratio on physical quantities such as drag and lift coefficients, Strouhal number and the vortex shedding mechanism are very notable in the range between 0 and 2. In general, the drag coefficient decreases with the aspect ratio and the decreasing rate is more distinct in the range of 0.15 ≤ R ≤ 2.0. There is no local maximum found at around R = 0.6 in the drag coefficient as reported for higher Reynolds numbers in the literature. However the root-mean-square value of the lift coefficient shows a maximum value at R ≈ 0.5 for all Reynolds numbers selected. The variation of Strouhal number with R appears to be different for four selected Reynolds numbers. Especially for Re = 250, a discontinuity in St, as has been observed for higher Reynolds numbers, is observed at around R = 1.45 where multiple peaks are found in the result of Fourier spectrum analysis of the lift force and irregular vortex shedding behavior with no fixed shedding frequency is observed from the instantaneous vorticity contours. Such discontinuity is not observed for Re = 100, 150 and 200. The present results using the LBM are compared with some existing experimental data and numerical studies. The comparison shows that the LBM can capture the characteristics of the bluff body flow well and is a useful tool for bluff body flow studies.

A computational study of flow past three unequal sized square cylinders at different positions

“…Here we include a short description of the numerical method and refer the reader to our previously [34][35][36][37] reported work for detailed discussion. The macroscopic fluid variables such as density and velocity are computed from the microscopic particles movement on a lattice from the main steps: streaming and collision.…”

Numerical Investigation of Incompressible Forced Convection in a Channel with a Rectangular Prism

“…Computational time and heat transfer accuracy compared with LBM code and commercial CFD code each other. Lattice Boltzmann Method examines the similar problem of forced convection in a rectangular obstacle channel [15][16][17]. Two studies [15,16] modelled just flow equation by LBM and one study [17] modelled flow equation by LBM and modelled energy equation by finite difference method.…”

Proximity Effects on Characteristics of Flow around Three Inline Square Cylinders

“…When one cylinder is immersed in the wake of another, the fluid flow characteristics strongly depend on the gap spacing ( ) between cylinders, geometric parameters related to cylinders arrangement, Reynolds number (Re), and shape of the cylinders [1][2][3][4]. Despite numerous investigations of the flow patterns and force coefficients of the flow past circular cylinders, very little attention has been directed toward the flow interference effects around an inline array of square cylinders [5][6][7][8][9][10].…”