University of Western Ontario
London, Ontario, Canada
Using a nonlinear, non-equilibrium critical layer analysis, we consider the nonlinear evolution a disturbance comprised two pairs of oblique waves superimposed on a mixing layer, with one pair inclined at an angle $\pm\theta_{1}$ to the mean flow and the other at an angle $\pm\theta_{2}$. When only one pair of waves is present, Goldstein and Choi (J. Fluid Mech. 207, 1989) showed that the evolution of the disturbance was governed by a nonlinear integro-differential equation of Hickernell-type with cubic nonlinearity. When the disturbance consists of more than one pair of waves, we show that there is an interaction between the pairs as well as within each pair, and that this can lead to enhanced growth.