Numerical Simulation of Flow Separation in a Thrust Optimized Parabolic Nozzle

Complex flow separation in thrust optimized parabolic nozzles in the over-expanded condition is one of the challenging issues of many numerical investigations. The correct estimation of a thrust optimized parabolic nozzle performance extremely depends upon the accurate estimation of the onset of flow separation. Literature review indicates that conventional Reynolds-averaged Navier–Stokes turbulence models have a significant error in predicting the onset of flow separation in these types of nozzles due to the overestimating of turbulent kinetic energy production. Recently proposed generalized k-omega has made it possible to rectify numerical simulations based on governing physics and using limited experimental results. In the present study, the flow physics in the LEA_TOC nozzle has been investigated with the numerical simulation approach. At the first, the significant error of conventional Reynolds-averaged Navier–Stokes turbulence models is shown to simulate flow separation in this type of problem. Then, the generalized k-omega parameters are modified based on the limited experimental result of the LEA_TOC nozzle, and the ability of this model has been evaluated to estimate the flow physics under different pressure ratios. Numerical investigations show that generalized k-omega has a high capability for accurately estimating the onset of flow separation at a wide range of nozzle pressure ratios. Applying the corrected generalized k-omega has resulted in an improvement of about 30% in the estimation of the onset of separation in the over-expanded LEA_TOC nozzle compared to the k-ω-SST model.