Controlled unsteady excitation of a reattaching flow
Abstract
The effect of a periodic velocity perturbation on the separation bubble downstream of a sharp-edged blunt face of a circular cylinder 16.5 cm in diameter, aligned coaxially with the free stream, is experimentally studied for the free-stream velocity of 12 m/s. Velocity fluctuations were produced from inside the cylinder through a 0.64-cm circumferential gap immediately downstream of the fixed separation line. A frequency scaling method is proposed, which correlates the asymmetrical Karman vortex shedding to the reflectively symmetrical separation bubbles which reattach on walls. The minimum drag was observed for Strouhal numbers in the range of 2 to 3. A comparison with results available on other geometries is made.
- Publication:
-
American Institute of Aeronautics and Astronautics
- Pub Date:
- March 1985
- Bibcode:
- 1985shfc.confR....R
- Keywords:
-
- Flow Visualization;
- Karman Vortex Street;
- Kelvin-Helmholtz Instability;
- Reattached Flow;
- Shear Layers;
- Unsteady Flow;
- Bernoulli Theorem;
- Reynolds Number;
- Scaling Laws;
- Sound Waves;
- Strouhal Number;
- Fluid Mechanics and Heat Transfer