Lambda shock behaviors of elliptic supersonic jets; a numerical analysis with modification of RANS turbulence model

Abstract

Abstract Supersonic jets have various applications in different industries, particularly as the propulsion of air-breathing engines and supersonic ejectors. The present study aimed to carry out a 3D numerical investigation of the outlet flow of elliptic nozzles of different aspect ratios and different length ratios of the convergent to the divergent part (called geometric ratio), as well as addressing the effect of tabs on the behavior of the outlet flow of the supersonic jet. In this regard, OpenFoam software was used alongside the pimple algorithm. First, the coefficients of the k-ω SST turbulence model were modified using experimental data, followed by the validation of the proposed method. The obtained results showed that β ⁎ of 0.075 led to the best state of predicting the behavior of the jet outlet flow. Then, the modified turbulence model was applied to investigate the effect of aspect ratios (the ratio of the major to the minor length of the supersonic jet outlet) of 2.5, 3, and 4, geometric ratios of 1.672, 1.106, 0.738, 0.48, and 0.2878, and triangular, square, and semi-circular tabs on the behavior of the outlet flow of the supersonic jet. By changing the above ratios, regarding the change in the slope of the divergent part, the flow separation region was affected, and the boundary layer-shock wave interaction altered. Further, the results indicated a change in the structure of shock waves and, in turn, dissipation of the output energy was inevitable.