Spectral Modelling of Transitional Boundary-Layer Coherence Breakdown

A model of the spectral energy content of a boundary-layer than has undergone the transition to turbulence is presented. Essential nonlinear energy transfer mechanisms are explicitly modelled and simplifications to the resulting statistics are obtained by considering the boundary-layer growth rate to be small as well as production to be effectively independent of local dissipation. Two perturbation parameters are introduced as a means of explicitly decomposing the compressible flow field into vortical, entropic and acoustic modes analogous to Kovasznay decomposition. A spectral representation of flow statistics is established under the assumed conditions that inhomogeneity only occurs in the wall-normal direction.