Unsteady Characteristics of Turbulent Flow Over a Rectangular Cavity

Unsteady characteristics of incompressible turbulent flow over a rectangular cavity were investigated with emphasis on its dominant frequency of oscillation and three dimensional features. Particle image velocimetry (PIV) measurements and fluctuating pressure measurements were carried out in a circulating water tunnel varying cavity length-depth ratio L/D=1 to 4 at Re_θ=8,300. It is found that the dominant frequency of the fluctuation decreases with the increase of the cavity length and it exhibits broadband behavior instead of resonant one. The instantaneous flow field shows strong three dimensional distortions. Present results indicate that the spanwise distortion may weaken resonant interactions between shear layer and cavity trailing edge.