Numerical Analysis of Flow Over Slitted Cylinder and Experimental Validation Using Soap-Film Technique

Low Reynolds number flow (Re = 100) over a slitted 2D cylinder was examined to analyze the flow characteristics within the slit and the role it plays on the shedding frequency. The goal of this work is to explore the enhancement of the lift and reduction of the drag for energy harvesting purposes. One way of achieving this goal is by controlling the separation of the incompressible laminar boundary layer through blowing and suction. However, in this work it is passively controlled by the cylinder slit. Different slit orientation (azimuth angles: 0, π/12, π/6, π/4, 5π/12, and π/2) at 10% slit-to-diameter ratio was considered. The work was carried out numerically by seeking solution to the unsteady Navier-Stokes equations. Validation was done experimentally utilizing the 2D vertical soap film tunnel available in our laboratory at Khalifa University. The visualization in soap film tunnel exploits the optical properties of soap film and relies on the wake formation patterns and the frequency at which vortices shed using well developed imaging techniques. These flow visualizations of the vortex shedding behind the cylinder with and without slit were recorded and analyzed to infer its Strouhal number (St = f.D/U). From the common Roshko’s graph (Re vs St) the Reynolds number was determined, and the film property was evaluated. Using common flow as baseline the technique can be used to validate numerous 2D-flow simulations, airfoils, bluff bodies, and even the oscillating flow around them. The details of the soap-film technique and parameters for successful experimentation are provided and demonstrated on slitted cylinder. The results are validated using numerical technique and the results from the literature.