The control of unsteady forces and wake generated in circular and square cylinder at laminar periodic regime by using different rod geometries

Abstract

The effects of the control rod geometry on the oscillating forces and vortex shedding of one circular cylinder, and another with square cross section were numerically investigated. The Reynolds number (Re) based on the diameter of the main cylinder (D) is fixed at 200. The solutions were obtained by applying the finite volume method to the Navier-Stokes in unsteady form. The control rods (CR) geometries are: square, circular, rectangle, and ellipse, accounting for different degrees of aerodynamic smoothness. The gap spacing between the main cylinder and CR was set to 0.2D, and their positions were varied in the angular range from θ = 0° to θ = 180° using intervals of 22.5°. For both main cylinders, the main flow features fall into three angular intervals, representing conditions of the rods immersed in the near wake of the main cylinders, located on their upper face, and frontally. In the first one, the fluctuating lift coefficient decreased up to 58% for the main circular cylinder by using a square rod. For the main square cylinder, the maximum reduction was 73%. The second range was characterized by gap flow formations which depended on the rod geometry and increased severely the lift forces. At the frontal angular position, the drag forces were reduced by rod interference. These results have many potential applications in the control of fluid structure interactions since cylinders with either circular or square cross sections are ubiquitous in the engineering field.