Prediction of Wake Structure Transition for a Linear Plug Nozzle Using Detached Eddy Simulation (DES)

Abstract

The base flow of a truncated plug nozzle exhibits a phenomenon called Wake Structure Transition (WST), where in an open base wake develops into a closed wake as the pressure ratio is increased. From design point of view, it is important to predict this transition. There are empirical models available for predicting WST but they are inaccurate for routine use in design. One physics-based model proposed by CAd lab of IISc, shows a potential to do the same with a great accuracy. However, its utility is limited by the requirement that accurate base pressure at two operating conditions, one in open and other in closed wake are to be known. The inherent limitations of RANS (or URANS)-based CFD solvers in predicting base pressure for large separated flows, limits the utility of aforementioned models. The present attempt explores the use of high-fidelity DES tool for the simulation of base flow and thereby WST prediction. The preliminary results obtained are very encouraging both from the view point of accuracy of the predicted base flow and its use in the physics-based model for predicting WST.