Assessment of parameters influencing the prediction of shear-layer mixing

A multisite team has completed an investigation of modeling high-speed mixi ng layers using the computational methods currently being applied to predic t high-speed civil transport (HSCT) nozzle flowfields. The objectives of th is investigation were to 1) calibrate the codes used by the various team me mbers against the same benchmark experimental data, and 2) assess the accur acy of the Navier-Stokes codes in calculating turbulent flows having now ch aracteristics similar to those of HSCT engine nozzles by varying user-speci fied input parameters, e.g., grid, turbulence model, boundary conditions. T wo how geometries were investigated using the Eve codes of NASTAR, PAB3D, G IF3D, NASTD, and NPARC. The first was the heated supersonic round jet. For this configuration, with a jet-exit Mach number similar to that of the prim ary now from miser chutes, three nozzle flow temperatures were investigated with the five codes. Using the same grid, boundary conditions, and kappa-e psilon turbulence model (in the mixing region), very similar results were o btained for all codes, but the solutions did not agree well with the experi mental velocity and temperature profiles. Further calculations using differ ent turbulence models, compressibility corrections, and axisymmetric dissip ation corrections improved the agreement with experimental data, but the co rrections are not universally applicable. The second configuration was a tw o-dimensional supersonic mixing layer. For the flow case examined, with two supersonic streams, the five codes again produced very similar results usi ng the same grid, boundary conditions, and turbulence model. The agreement with experimental data was better than for the round nozzle. Based on the r esults of this investigation, it was determined that consistent nozzle flow predictions may be obtained by the team members using the different codes investigated hereby using consistent computational grids, boundary conditio ns, and turbulence models. The deficiencies of these codes in predicting hi gh-temperature compressible jets were identified and are directly related t o the turbulence models currently employed. The consistency that was achiev ed will allow for a computational fluid dynamics procedure to be establishe d for performing a multisite parametric design and analysis effort by the t eam members.