Spectral Analyses Study of Boundary Layer Transition Delay with a Finite Compliant Panel

Abstract

Compliant panel or surface has been demonstrated in various theoretical investigations as a promising means in delaying transition further. Within the Blasius boundary layer, wavepackets was initiated at the flow upstream with a pulse-initiated disturbance, and this was allowed to evolve over a finite section of the wall that was replaced by a tensioned compliant panel (CP) on a damped foundation. In order to appreciate the work of the CP in transition delay, direct numerical simulation (DNS) was also carried on the rigid wall (RW) case for comparison purposes. Spectral (Double-Fourier transforms) analyses was performed on the obtained DNS data, and the results showed that, CP case was able to delay transition further, through the strategy of suppressing the linearly growing primary 2-D Tollmien-Schlichting (TS) waves mode, so that resultant wavepacket after the CP location was dominated by a pair of oblique waves. The practical implication of the obtained results show the possibility of drag force reduction over moving vehicles, which will translate to tangible economic gains for the total amount being spent on fuelling especially for those in transportation businesses.