Investigating flow patterns in a channel with complex obstacles using the lattice Boltzmann method

Abstract

In this work, mesoscopic modeling via a computational lattice Boltzmann method (LBM) is used to investigate the flow pattern phenomena and the physical properties of the flow field around one and two square obstacles inside a two-dimensional channel with a fixed blockage ratio, 1 4 β = , centered inside a 2D channel, for a range of Reynolds numbers (Re) from 1 to 300. The simulation results show that flow patterns can initially exhibit laminar flow at low Re and then make a transition to periodic, unsteady, and, finally, turbulent flow as the Re get higher. Streamlines and velocity profiles and a vortex shedding pattern are observed. The Strouhal numbers are calculated to characterize the shedding frequency and flow dynamics. The effect of the layouts or configurations of the obstacles are also investigated, and the possible connection between the mixing process and the appropriate design of a chemical mixing system is discussed.

Validation of LBM based on BGK on Poiseuille s Flow and Vortex Street in a Channel Flow

“…In the streaming stage, particle at position x after time dt move to x+dx in the direction of its velocity. The collision stage involves only those, real valued particle distribution function arriving at each node although in some other cases (such as multicomponent and multiphase flows) particle distribution function at other nodes may also influence the collision step [6].…”

The lattice Boltzmann method for investigating the fluid flow pattern in 2D channel through triangle obstacle

“…An unstable flow pattern which consists of a periodic vortex shedding pattern behind the obstacle is called a von Karman vortex street. In order to make a detailed comparison of the velocity profiles of the flow pattern phenomena, we found that the Re crit for the flow pass a triangle obstacle is less than the Re crit for flow pass a square obstacle in [12] whereas the same parameters investigations. It was noticed that the flow pattern pass the triangle obstacle generates periodic vortex shedding patterns more quickly than the flow pattern pass square obstacle as shown in Figure 4.…”

“…It can be seen that there are large fluctuations in velocity for most of the length of the channel but that the fluctuations become small in far wake near the channel outlet. Moreover, we found that the velocity behind the triangle obstacle is more fluctuations than the velocity behind the square obstacle (see Figures 5(a) The instantaneous velocity at the centerline of channel for Re 100 = (a) a triangle obstacle and (b) a square obstacle [12].…”

“…The top reviews of the studies on flow past circular cylinders under free flow conditions have been widely written by Williamson [5] and Zdravkovich [6]. Whereas the publication on the flow past square cylinder [4,[7][8][9][10][11][12] were investigated both experimentally and numerically, for a wide range of Reynolds number and different blockage ratios between 1 20 and 1 5 . For example, Breuer et al (2000) [4] presented accurate computations of the laminar flow past a square bar in a channel using two different methods (FEM and LBM).…”

“…Comparison of velocity profiles for Re=60 (a) around a triangle obstacle (b) around a square obstacle[12].…”