CFD ANALYSIS AND REDUCED ORDER MODELING OF UNCONTROLLED AND CONTROLLED LAMINAR FLOW OVER A CIRCULAR CYLINDER

The main idea of flow control is the improvement of aerodynamic characteristics of flow. This study analyzes the laminar flow over a two-dimensional (2D) circular cylinder and its control by air blowing from several slots located on the cylinder surface, computationally. The Computational Fluid Dynamics (CFD) results are validated using the experimental results available in the literature for Strouhal number, time-averaged drag coefficient and pressure coefficient distribution around the cylinder. Air blowing from four slots on the cylinder with a velocity of 50% of the free-stream velocity yields a reduction of the drag coefficient by 9%. Flow structures are separated according to their frequency content by Proper Orthogonal Decomposition (POD) method. It is seen from POD results that 99% of the total energy content can be modeled by considering only four most energetic POD modes of the flow. POD analysis of the controlled cases also show that the flow structure around the cylinder changes with the help of air blowing. For real-time flow control applications, it is important to predict the flow based on surface sensors, placed at a few discrete points. In this study, optimum sensor locations on the cylinder surface are also obtained by utilization of a one-dimensional POD analysis based on surface pressure data obtained from CFD results.