Assessment of RANS Turbulence Models for the Simulation of Turbulent Compressible Flows in Convergent-divergent Nozzles

Abstract

The main objective is to analyse gas flow dynamics in a Convergent-Divergent (CD) nozzle and predict its behaviour under various conditions. The model assumes adiabatic, impermeable walls with bidimensional, compressible, steady, subsonic, and turbulent flow. Conservation equations for mass, energy, and momentum form the basis of the mathematical model, which is solved using Reynolds-Averaged Navier-Stokes turbulent models including Standard k-e, Realizable k-e, Standard k-?, and Shear-Stress Transport k-?. Evaluation of these models across different Nozzle Pressure Ratios (NPR) shows that Shear-Stress Transport k-? correlates best with experimental data on static pressure. Three ANSYS products: DesignModeler, Meshing, and Fluent, are used for numerical simulation. The methodology reliably predicts phenomena such as flow separation, Mach disc formation, and nozzle exit regime, crucial for safe and efficient system operation.