Farooq Ahmad Najar’s scientific contributions

Flow separation is one of the prominent yet undesirable effects found in flow fields, either over the external surfaces like airfoils or inside of surfaces like flow through nozzles. Efforts have always been on, to prevent the flow separation wherever it occurs. One more effect is of paramount interest-shock formation as a result of compressibility of flows. In this paper, an effort is made to study the flow separation and shock formation in convergent-divergent nozzles using computational fluid dynamics. The modeling of nozzle is carried out in Gambit 2.2.30, which is a CFD preprocessor and the analysis-simulation is carried out in Fluent 6.3.26 which is a CFD processor. The models employed for study are Inviscid and K-ε turbulence model. It is found that the inviscid flow solution shows a straight shock instead of a curved shock. In viscous flow, velocity is less near the wall (i.e., in the boundary layer). So, the shock takes place near the wall before it takes place in the main flow. Hence the shock location near the wall is upstream to the shock location near the axis resulting into a curved shock. The viscosity accounts to loss in momentum. As this loss is not considered in inviscid flow, a higher maximum Mach number is obtained.