Skip to main content

Effect of the Acoustic Black Hole on the turbulence transition of a laminar boundary layer flow over a compliant panel

Start year: 2025

Summary: The boundary layer flow transition to turbulence in a low noise environment takes place through the linear development of the fluid based on the 2D Tollmien-Schlichting waves (TSWs). This first stage of the transition is significantly longer than the later stages of the nonlinear development of the 2D and 3D waves and turbulent spots. The use of a compliant wall with proper structural properties can significantly extend the linear development of the convectively unstable 2D TSWs before entering to the next stage of the transition by reducing their spatial amplification rate [1,2]. In this way, the laminar boundary layer flow can be extended for a larger total length relative to the rigid wall with the concomitant significant reduction of the skin-friction drag. Recently, it was demonstrated that for a finite length compliant wall the TWF and TSW instabilities become globally unstable and the flexural waves travel and grow along the whole finite length of the compliant wall because of their reflection at the compliant wall ends [5,6]. This could have a deleterious effect on the delay of the turbulence transition which could take place earlier than the rigid wall case. This project will investigate the Acoustic Black Hole (ABH) as means for diminishing the amplification and reflection of the TWF and TS waves at the compliant wall ends, maintaining their convecting nature and contributing to the optimization of the compliant wall for transition delay.