Abstract
This paper presents the three-dimensional flow investigations over the square cylinders placed in the tandem arrangement. Two different flow configurations were investigated in detail; one comprising of a single square cylinder and the other comprising of three square cylinders placed in a tandem arrangement with the spacing of six times the width (w) of each square cylinder. The Reynolds number based on the width of the square cylinder (w) and free stream velocity (Uo) is 22,000. The problem was solved numerically using an Unsteady Reynolds-Averaged Navier-Stokes (URANS) based model and Large Eddy Simulation (LES) based model. Strouhal Number, lift, and drag coefficients were computed for each configuration. By comparing both the models using contour plots of pressure, velocity and vorticity it is found that the LES model is more accurate to capture the turbulence around single and tandem square cylinders. In the tandem arrangement, complex periodic vortex shedding was observed in the wake of each square cylinder. The production of turbulent kinetic energy was also investigated to understand the roles of stresses during flow over the cylinders. The analysis showed that the production of turbulence by normal stresses is higher than that of shear stresses. Furthermore, it was observed that the flow over the first cylinder arranged in tandem is quite identical to that of the single square cylinder. Moreover, the upstream cylinder experienced a higher lift in comparison to the downstream cylinders.
Highlights
Over the last century, flow over bluff bodies is the subject of intense investigations both numerically and experimentally
The lift and drag coefficient were found to be sinusoidal in nature which ensured that the primary (Strouhal) frequency pertaining to the vortex shedding was the dominant frequency and there waws no significant contribution of the secondary-frequency
The flow field over a single square cylinder and three square cylinders placed in a tandem arrangement are investigated using different numerical models
Summary
Flow over bluff bodies is the subject of intense investigations both numerically and experimentally. The flow field in the wake region of different bluff bodies including circular, square and triangle crosssection cylinders was experimentally and numerically investigated by Yagmur et al [10]. Olsen et al [22] performed an intensive literature review including a study and comparison of different CFD models for analyzing the there are extensive investigations of flow over a single square/ circular cylinder and tandem arrangements of circular cylinders, there are remarkably few investigations were made for the flow over a row of non-circular cylinders at high Reynolds number. The lift and drag coefficient were found to be sinusoidal in nature which ensured that the primary (Strouhal) frequency pertaining to the vortex shedding was the dominant frequency and there waws no significant contribution of the secondary-frequency Fluid forces and their discontinuity acting on two square prisms in a tandem arrangement were experimentally analyzed by Alam et al [28] at Re of 5.6×104.
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