Axisymmetric mixing layer - Influence of the initial and boundary conditions

The discrepancies among published shear layer data, presumed to be due to effects of differential initial and boundary conditions existing in different experiments, were explored by measuring the average characteristics of four mixing layers: two asymptotically limiting initial conditions (namely, laminar and turbulent), each with two distinctly different boundary conditions (namely, with and without a large-diameter end plate). It is found that the two boundary conditions produce essentially identical evolution for the mixing layer for either choice of the initial condition. For initially laminar cases, there is a noticeable effect of the exit plane geometry for a small x range, presumably through modification of the initial vortex rollup and pairing. The data are in qualitative and quantitative agreement with plane mixing layer results.