03.3 - Basic Fluid Dynamics and Flow Control
STABILITY OF A LAMINAR BOUNDARY LAYER OVER LOCALISED SURFACE INDENTATION
E.R. Gowree, ISAE-SUPAERO, France; C.J. Atkin, University of East Anglia, United Kingdom
Experimental evidence of the co-existence of both an artificially excited convective mode and a natural mode in a confined laminar separation bubble is presented. The naturally excited mode takes the form of a wave-packet which became clearer when wavelet transform was applied to hot wire measurements. This mode had a characteristic frequency centred at a Strouhal number approximately 1 based on the freestream velocity and length of the bubble. It appeared to grow rapidly both in time and space, where the linear spatial growth is similar to the artificial convective mode, suggesting that the noise introduced in the system by the feedback loop from the bubble oscillation triggers an amplifier dynamics.