Reynolds stress transport models in unsteady and non-equilibrium turbulent flows

In this work the predictive capability of a number of Reynolds stress transport (RST) models was first tested in a range of non-equilibrium homogeneous flows, comparisons being drawn with existing direct numerical simulation (DNS) results and physical measurements. The cases considered include both shear and normally strained flows, in some cases with a constant applied strain rate, and in others where this varied with time. Subsequently, the models were also tested in the inhomogeneous case of pulsating channel flow over a wide range of frequencies. were generally found to perform well in homogeneous shear at low shear rates, but their performance increasingly deteriorated at higher shear rates. This was attributed mainly to over-predicted shear stress anisotropy at high shear rates. Performance in irrotational homogeneous strains was generally good, and was more consistent over a much wider range of strain rates. pulsating channel flows, the most challenging case for the models was found to be the lowest frequency case where, because of the amplitude of oscillation, laminarization and re-transition to turbulence were present at certain phases of the cycle.