CONTROL OF FLOW AROUND A SQUARE PRISM BY USING SYNTHETIC JET

Control of the flow around a square prism by means of synthetic jet through a single slot located on middle of upper surface of the model has been investigated experimentally for Reynolds number of 8000. Synthetic jet was implemented by using a pneumatic piston-cylinder which was driven by means of an electrical motor. The frequency and stroke of the piston were changed to obtain various values of the flow control parameters. For various excitation frequency and momentum coefficients of the synthetic jet, the mean and fluctuating pressure distributions on the square prism were measured. The velocity measurements at the slot exit and at a specific coordinate were conducted by means of constant temperature anemometer (CTA). Vortex shedding frequencies obtained by the spectral analysis of both pressure-time and velocity-time history. At a value of synthetic jet excitation frequency, vortex pairs generated at slot were perturbed the shear layer that separated from the upper leading edge of square model and disturbs it. When the synthetic jet excitation frequency closes enough to the vortex shedding frequency, the lock-in of vortex shedding frequency onto the exciting frequency was occurred. On the other hand, increasing excitation frequency of the synthetic jet causes a pressure recovery on the surface of the prism within the wake region. The efficiency of the synthetic jet is classified depending on change of the drag coefficient and vortex shedding frequency.