Characterization of Frequency Mode inside an Open Cavity for Different Shape Ratio

A number of studies have referred to the existence of a vortex cell within an urban street canyon. The understanding of vortex dynamics or vorticity distribution is a such configuration is of great interest. This configuration was simulated by the interaction between a boundary layer and a cavity. Experimental characterization of the vortex structures evolution was developed by the technique of measure Particle Image Velocimetry (PIV). In this paper, we have studied and characterized experimentally by the technique of measure Laser Doppler Velocimetry (LDV) the vortex escape frequencies. Measurements were performed for different cavity shape ratio and for different mean velocities. Where the ratio between the shear instability process and the mechanisms of frequency selection which depend of the size of the cavity. The evolution of the system by the variation of the number of Strouhal according to the number of Reynolds, led us to a regrouping for every mode, permitting to really separate the mode the some of the other.