Investigations of entrainment characteristics and shear-layer vortices evolution in an axisymmetric rear variable area bypass injector

Abstract In this study, firstly, for the axisymmetric RVABI, the change-rule of adverse pressure gradient caused by radial velocity during the transition of internal flow mode in variable geometry is summarized, and a Bypass Ratio (BR) iterative algorithm based on the empirical correlation of non-equilibrium pressure is proposed. The algorithm can estimate the nonlinear relationship between area ratio and BR, with an error range falling below 6.5%. Then, we discuss the favorable effect of uniform mixing on the thrust augmentation of mixed exhaust under variable BR conditions. From this point of view, The characteristics of vortices evolution in different shear strength jets are compared, to clarify the effect of variable cycle parameters on jet mixing. As the results suggest, when Λ is as low as 0.22, the K-H disturbance is of high-frequency wavelet property, and it is difficult to induce large-scale spanwise vortices. The macro migrations of fluid elements in spanwise vortices and the diffusion effect caused by edge tearing is weak, which is not conducive to the energy exchange between the two streams. However, the low Λ jet will also correspondingly weaken the viscous dissipation effect of vortices. It is concluded that the dissipation level is proportional to the 2.31 power of the Λ .