Pressure-based Coupled Numerical Approach to the Problem of Compressible Flow through Convergent Conical Nozzles

摘要

The problem of high-speed compressible flow through convergent conical nozzles is studied computationally using the general purpose CFD code ANSYS Fluent. A pressure-based coupled solver formulation with weighted second-order central-upwind spatial discretizations is applied to calculate the numerical solutions. 15, 25 and 40 deg axisymmetric conical nozzles, and a reference nozzle with a circular arc cross section are considered. In addition, a 3D configuration of the 25 deg nozzle with a thin splitter plate sandwiched between the two halves of the axisymmetric nozzle is included to investigate the effect of the splitter on the shock location. A hierarchy of axisymmetric hybrid computational meshes is constructed to evaluate grid independence. A solution-based adaptive mesh refinement is applied to increase resolution across the shocks, and to provide an additional case matrix for a grid independence study at supersonic conditions. Effects of turbulence modeling are evaluated by comparing SST k-ω and Renormalization Group (RNG) k-ε. Numerical predictions of discharge and thrust coefficients, Mach numbers inside and at the nozzle exit, and shock locations are compared with the experimental data and excellent agreements are presented. A transient simulation using the Delayed Detached Eddy Simulation (DDES) turbulence model is carried out to investigate the effect of vortex shedding off the splitter trailing edge, and an estimate of shedding frequency is provided.