"Effect of unsteady wake-passing frequency on boundary layer transition --- experimental investigation and wavelet analysis"

by
Schobeiri, M.T., Read K., and Lewalle, J.

ABSTRACT

Detailed experimental and theoretical investigations have been carried out to study the effect of unsteady wake passing frequency on the boundary layer transition along a curved plate under zero longitudinal pressure gradients. Periodic unsteady flow with different passing frequencies is generated utilizing an unsteady flow research facility with a rotating cascade of rods positioned upstream of the curved plate. Extensive boundary layer measurements are carried out. The data is analyzed using conventional and wavelet-based methods. Local timescales are defined as those of the most energetic fluctuations, and are calculated from wavelet transforms of the velocity signals. The dominant time scales are mapped as functions of the distance to the plate, the downstream location, and the phase relative to the wake-passing. Furthermore, conditional sampling is applied, laminar time scales are calculated and the effects of wake-passing frequency on these scales is shown.