Numerical Simulation of the Flow Around a Surface-Mounted Finite Square Cylinder

Large eddy simulation (LES) was used to study the unsteady turbulent flow over a surface-mounted square cylinder of finite height, for cylinder aspect ratios of AR = 3 and 5, at a Reynolds number of Re = 500. Employing a semi-implicit fractional step method for momentum and a pressure correction scheme for mass conservation, a collocated finite-volume code was used to solve the Navier-Stokes equations in three dimensions. A multi-grid scheme was employed to accelerate the pressure solver. The cylinder geometry was created on a Cartesian mesh using internal boundary conditions. The motivation for the study was to better understand the complex wake structure of the finite cylinder and the influence of the aspect ratio. The numerical results were consistent with the observations from experiments documented in the literature. For the case of AR = 3, the wake was dominated by downwash effects, where as for more slender cylinder, AR = 5, some upwash effects were noticeable closer to the ground plane.