Experimental characterization of the flow within a transitional rectangular cavity

A rectangular cavity with a length-to-depth ratio of 10 is characterized by means of two optical velocimetry systems: Laser Doppler Velocimetry (LDV) and Particles Images Velocimetry (PIV). Each of these two measurement systems provides a complementary contribution to the understanding of this complex flow. A detailed mean velocity field is acquired by LDV, it shows the presence of a thin fluid layer near the bottom wall where the flow goes upstream all along the cavity which is qualified to be transitional and includes a stagnation point within the flow. PIV measurements enable the detection of coherent structures in the flow and the analysis of their evolution near the stagnation point where they interact with the bottom wall. Three different zones are specially studied by a spectral analysis of the LDV velocity signals to define the main detachment frequency of coherent structures.