Transitional Periodic Boundary Layer Study

The experiments indicated that this type of flow can be turbulent at a Reynolds number considerably lower than the ciritical value for transition for flow over an oscillating flat plate. Detailed velocity measurements have been made using laser Doppler Anemometry and a digital data acquisition technique to isolate and measure the periodic and random components of the velocity. These data indicate that the behavior of the periodic aspect of the transitional flow is only mildly different from that predicted for a laminar periodic flow at the same oscillation frequency. The turbulent intensities while being lower than for fully turbulent boundary layers have been found to be still significant throughout the cycle. Some implications of the present results with regard to the measurement and interpretation of transition data in oscillatory flows are examined.