A Numerical Investigation of Turbulent Flow Over Single and Tandem Square Cylinders

Mahrukh Mahrukh; Usman Allauddin; Mohammed Ehteshamul Haque; Naseem Uddin; Ahmed Hussain

doi:10.22581/muet1982.2104.04

Mahrukh Mahrukh Department of Mechanical Engineering, NED University of Engineering and Technology, Karachi, Sindh, Pakistan.
Usman Allauddin Department of Mechanical Engineering, NED University of Engineering and Technology, Karachi, Sindh, Pakistan.
Mohammed Ehteshamul Haque Department of Mechanical Engineering, NED University of Engineering and Technology, Karachi, Sindh, Pakistan.
Naseem Uddin Universiti Teknologi Brunei Brunei Darussalam.
Ahmed Hussain Department of Mechanical Engineering, Hamdard University, Karachi, Pakistan.

DOI: https://doi.org/10.22581/muet1982.2104.04

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.