Passive and active control for flow over a cylinder using a slit and validation with soap film technique

The flow over a slitted (0.1D) cylinder is studied numerically and experimentally using CFD and soap film at Re = 100 at varying slit angles (0 degrees -90 degrees). The numerical solution is obtained by solving the Unsteady Reynolds-Averaged-Navier-Stokes (URANS) equations, and coefficients of lift (CL) & drag (CD), velocity, and vorticity are analyzed. Experimentally, soap film is used to visually validate the scaler data of the flow pattern. It exploits the optical properties of soap film captured by a highspeed camera by the reflection of a monochromatic sodium lamp light. The passive control of the slit is observed at various slit angles that affects the lift and drag and injection and blowing/suction modes. The active control is carried out by oscillating a thin wall placed in the middle of the 90 degrees slit with varying frequency and amplitude. The results show that passive slit does not change the overall flow pattern and with slight changes in the CL and average CD. However, greater influence occurs by actively changing the amplitude and frequency of the wall oscillation. The CL amplitude is increased with increasing frequency of wall oscillation, but the average CD only increased at the lock-in condition and slightly decreased at the other frequencies.& COPY; 2022 Elsevier Masson SAS. All rights reserved.