The Numerical Study Of The Enhancement Effect In 3D Supersonic Mixing Layer With Swirl

In the Scramjet, the mixing competence of the fuel and air is directly related to the flight performance of supersonic aircraft. However, owing to large compressibility in the supersonic mixing layers, the mixing efficiency of flow is very low. Therefore, it is very necessary in theory analysis and practical application to explore a new method to enhance mixing. The basic flow constituted by amending Blasius solution is took into the 3D compressible N-S equation in cylinder coordinates to solve it. The nonlinear evolution of the disturbance in compressible swirling mixing layer is studied by introducing the T-S waves at the inlet of the computational domain. Some factors, involving spanwise curvature, spanwise velocity, disturbance frequency and Mach number, are presented to enhance mixing. The conclusions are listed as follow:1. When the convection Mach number is close to 1, the frequency of the unstablest waves in plane mixing layer is small as well as the maximum amplification rate. However, the maximum amplification rate in swirling mixing layer obviously increases, and the frequency range of the unstable waves of the swirling mixing layer is wider. The disturbance wave that grows fastest is high frequent 3D wave.2. With the augmentation of spanwise curvature and velocity, the peak value of disturbance in radial direction becomes large, and the momentum thickness, vortices value and the rolling area of vortices are also increased.3. During the evolution of the high frequent 3D disturbance in downstream flow for swirling mixing layer, the streamwise vortices break down and spanwise vortices draw towards the swirling center of the base flow. The second wave crest appears near the side of swirling center in the distribution of the maximum disturbance amplitude, and three inflection points emerge in the mean velocity profile.4. For the mixing layer with spanwise curvature and velocity, the maximum amplification rate slightly decreases along with the increase of Mach number. But mixed area is easer to enlarge in radial direction, which is propitious to mixing.