Laminar-turbulent transition of supersonic boundary layer in the presence of external disturbances

Abstract

A method for estimating the location of the laminar-turbulent transition is described, which is based on the theory of linear stability under the condition of the acoustic field presence. In the stable region near the stability loss location, the amplitude of the velocity disturbances is determined, which are excited by an external sound wave. By virtue of the proximity of sound wave parameters and proper oscillations, the obtained value of the amplitude is accepted to be equal to the amplitude of the growing wave of the boundary layer. At some downstream point, the Reynolds stresses corresponding to this amplitude become equal to several percents of laminar stresses of the undisturbed boundary layer. Based on experimental data it is accepted in the work that at the transition onset, the Reynolds stresses amount to 12 % of laminar stresses.

The use of the proposed criterion accounting for external disturbances gives a good agreement between the computed and experimental data. Right up to the transition, the growth of disturbances in boundary layer is described well by the linear equations of stability.