Cfd analyses of uncontrolled and controlled laminar and turbulent flows over a circular cylinder

External flow over a bluff body causes time-dependent and periodic behavior behind of the body when the Reynolds number of the flow is greater than a certain value. For external flow over a circular cylinder, these oscillations are generated in both laminar and turbulent flow regimes. A control strategy can be developed to damp the oscillations or to reduce the effects of the oscillations on the cylinder.The main idea of flow control is the improvement of aerodynamic characteristics of flow, such as, reducing drag and unsteadiness of loads compelled by the flow field onto structures exposed to the flow. This study analyzes the laminar and turbulent flows over a two-dimensional (2D) circular cylinder and its control by air blowing from several slots located on the cylinder.CFD analyses were performed for both laminar and turbulent flows. In turbulent flow analyses, Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations are solved and Spalart-Allmaras turbulent model is used. CFD analyses were validated by using the experimental values for Strouhal number, time-averaged drag coefficent and pressure coefficient distribution given in literature.Air blowing from four slots with a magnitude of 50% of the free-stream velocity yields a reduction in drag force by 8.6% and 23.3% compared to the uncontrolled case for laminar and turbulent flow, respectively.Also, three-dimensional CFD analysis of uncontrolled turbulent flow over a cylinder was performed and the results were compared to the one obtained by 2D CFD analysis to investigate the accuracy of two-dimensional simulations for this type of flow.