Research on efficient active T-S wave generation method in boundary layer

The transition of the boundary layer is closely related to the flight of the aircraft. The laminar boundary layer is favored because of its low friction drag. In order to control the T-S instability, a set of T-S waves can be artificially excited in the boundary layer. Its phase is opposite to the phase of the T-S wave excited by the external disturbance, and the two are linearly superimposed, thereby reducing the amplitude of the total T-S wave and delaying the occurrence of the transition. In this paper, T-S waves excited by various disturbances are studied by Direct Numerical Simulation (DNS) and compared with Linear Stability Theory (LST). Some of the results are reproduced in wind tunnel experiments. The receptivity phenomenon of the laminar boundary layer over a zeropressure-gradient flat plate is analyzed, and the results obtained by three research methods are in good agreement. Firstly, the characteristics of the T-S waves excited by single-period wall blowing and suction disturbances, referred to as the "elementary wave" (EW), are analyzed and organized. The amplitude of the EW does not conform to the Linear Stability Theory, and its frequency is not entirely equal to the disturbance frequency. Subsequently, the study finds that as the number of disturbance periods increases, the amplitude of the T-S waves at some streamwise locations exhibits a characteristic where the amplitudes at the beginning and end are greater than those in the middle. Then, six intermittent blowing and suction forms are proposed, and a quantitative comparison of these six blowing and suction control methods is carried out. Ultimately, an efficient method for generating T-S waves that can reduce the pump drag by more than 12% is proposed.