Transverse Forcing on Supersonic, Spatially Evolving Mixing Layers

Abstract

Large eddy simulation (LES) of supersonic, spatially evolving mixing layers is performed. A transverse perturbation is introduced to force the development of the mixing layer. Special attention is paid to the effect of forcing frequency and amplitude on the properties of large-scale structures and growth characteristics of the mixing layer. Instantaneous plots of discrete vortices and thickness of the mixing layer are obtained to examine the variation of coherent structures and the spatial spreading rate. Results show that transverse forcing has a huge effect on the initial development of the mixing layer. The forcing frequency is able to govern the eddy roll-up and interactions, and the size of saturate eddies is determined by the convective velocity and forcing frequency and is independent on the forcing amplitude. A high forcing frequency and amplitude can enhance the initial spreading rate. In addition, two-frequency forcing with a high amplitude is suitable for increasing the spreading rate and promoting scalar mixing.