Coherent Turbulent Stresses in Unsteady Forced Transonic Nozzle with Shock-Induced Separation

The influence of rotor/stator interference on shockwave/boundary layer interaction is investigated by means of an implicit large-eddy simulation. To replicate actual turbomachinery conditions but at a lower cost, this work considers a transonic bump over which a shock-wave develops and interacts with the separated boundary layer. Moreover, the backpressure is set to fluctuate at a realistic reduced frequency. The analysis is focused on the coherent component of the flow and more particularly the turbulent stresses in the recirculation region. Phase-averaging is performed in order to highlight this component and the reference oscillator is based on the location of the separation point. Statistical convergence is assessed. Coherent turbulent stresses show a two-layers pattern, the upper layer being linked to the mixing layer and the inner layer developing below. The coherent component can reach up to 60% of the local mean value. Budgets show that only some production terms are significant and each of them is acting upon a specific layer of the associated coherent turbulent stress. Finally, pressure strain, responsible for the coupling between the transport equations, is also of importance