Self-sustained oscillation of the flow in a double-cavity channel: a time-resolved PIV measurement

This study investigates self-sustained oscillation of the flow in a double-cavity channel with cavity length–width ratio L / H = 3 using a time-resolved particle image velocimetry (TR-PIV) technique. Three Reynolds numbers based on the cavity length L and the bulk velocity in the narrow section of the channel U 0 , i.e., R e L = 12,500, 24,580, and 49,100, are considered to investigate the influence of Reynolds number on the self-sustained oscillation. As the Reynolds number increases, the oscillation becomes more intense and shifts to the leading edge of the double-cavity channel. However, the power spectra and contour plots of the spatial v – v correlation coefficient reveal that the periodicity of the oscillation becomes less profound as the Reynolds number increases. A further phase-averaged analysis reveals the spatiotemporal evolution process of oscillation and convincingly demonstrates a more intense and complicated process of the oscillation as the Reynolds number increases. Graphic abstract