Resolved scalar mixing in large eddy simulations of a low reynolds number plane mixing layer

In this paper we present Large Eddy Simulations of a low Reynolds number plane mix- ing layer. The purpose of the research is to assess the effect of inflow conditions on the scalar mixing in the flow. A high-resolution grid is used to study a pre-transition mixing layer originating from initially laminar conditions. Both pseudo-random white noise and physically-correlated fluctuations produced by an inflow generation technique provide the background fluctuations for the simulations. It is found that the scalar statistics are largely spanwise invariant when pseudo-random fluctuations are employed, whilst large spanwise variations in the scalar statistics are observed when physically-correlated fluctuations pro- vide the background disturbances. The large fluctuations are attributed to the presence of organised streamwise vortices in the mixing layer. The implications of this research in terms of the documentation of experimental initial conditions is discussed.