Fluidic Oscillation Influences on V-Shaped Bluffbody Flow

Abstract

The V-shaped fluidic oscillator is developed by inserting a target blockage with a specially designed crescent surface into the downstream cavity of a slit V gutter. Stable, self-sustained, periodic fluidic oscillations can be induced by the dynamic Coanda effect when the geometric parameters of the target blockage and the Reynolds number are properly tuned. The fluidic oscillations are directed through two slit passageways and injected into the near wake of the V-shaped fluidic oscillator like pulsing jets. The oscillation behaviors, frequency selection, streamline patterns, and turbulence properties of the unsteady flows in the near wakes of the V-shaped fluidic oscillator are studied experimentally in a wind tunnel by using the smoke-wire flow visualization technique, hotwire anemometry, and laser Doppler velocimetry. Flowfields of the slit V gutter and the closed-tip V gutter, which are the counterparts of the V-shaped fluidic oscillator, are also measured for comparison. The Strouhal number of the fluidic oscillation based on the slit width of the presently developed oscillator can attain a value of about 0.56 at large Reynolds numbers, which is about 80 times larger than the previous results for the enhancement of heat transfer and about 60 times larger than that for the fluidic flowmeter. The fluidic oscillations act as an excitation source for the wake. The kinetic energy of the fluidic oscillations is transferred to turbulent fluctuations and therefore causes increases in the size of the recirculation bubble and the turbulence intensity in the wake of the V-shaped fluidic oscillator. The turbulence intensity in the near wake can be increased by about 7% when compared with that of the closed-tip V gutter.