Resolved Scalar Mixing in Large Eddy Simulations of a High Reynolds Number Plane Mixing Layer

In this paper we present the results from a series of Large Eddy Simulations of the initially-laminar plane mixing layer. Local Reynolds numbers, based on the velocity differ- ence across the layer and its visual thickness, of up to 200,000 are achieved. The purpose of this study is to assess the effect of inflow conditions on the resolved scalar mixing in the flow. When a white-noise disturbance environment is applied to the inflow condition, there is an absence of a spatially stationary streamwise vortex structure, the turbulent coherent structures grow continuously and linearly, and the scalar probability density functions are titled in nature. When a physically-correlated disturbance environment is applied to the inflow condition, a spatially stationary streamwise vortex structure is present in the flow, the turbulent coherent structures grow continuously and with the square-root of time, and the scalar probability density functions are non-marching. The mixed fluid statistics obtained from the latter simulation type agree well with comparable experimental data. This research suggests that different entrainment mechanisms are possible in simulations of plane mixing layers, dependent on the type of inflow condition used.