Spatially developing laminar mixing layer forced by velocity and thermal perturbations downstream of a splitter plate

Abstract

In this work our first objective is to study the spatial development of a laminar compressible mixing layer after a splitter plate at relatively high Reynolds number by using an implicit large-eddy simulation. A blowing and suction strip is used on the upper wall of the plate to promote the shear layer instability. In the perspective of flow control our second objective is to understand the effects of a strong thermal forcing to modify the spatial development. In the momentum-forcing case three distinct flow regions exists: a linear instability region, a mixing-transition region and a fully developed turbulent region, which has much different vorticity growth rate. In the fully developed region the distributions of mean velocity collapse into a self-similar profile. There is no spanwise roller observed near the trailing edge of the plate. When the thermal forcing is also applied, it introduces two-dimensional spanwise rollers. Two successive spanwise roller pairing are observed. The vorticity thickness and its growth rate are totaly different. At the end of the simulation domain the flow is not fully turbulent. Different Mach wave radiations are observed in the fast stream. Therefore, the thermal forcing can effectively to modify the spatial development of the mixing layer.