Large eddy simulation of turbulent flows in reversing systems

Curved flows observed in aeronautical reversing systems are studied using large eddy simulation (LES). To estimate the prediction capabilities of LES, a curved mixing layer is first simulated. The major effect of curvature is to decrease the level of turbulent fluctuations, a decrease that is followed by an overshoot of fluctuations when the flow relaxes further downstream. These observations agree well with previous experimental investigations of curved mixing layers. The simulations of a thrust-reverser test case reveal that large scale spanwise motions play a crucial role. Specifically, they overcome the decrease of turbulent fluctuations in the curved zone. The properties of the flow contributing to the reverse thrust developing at the exit of the reverser may then strongly depend on the behaviour of the unsteady coherent large scales.