In Silico and In Vitro Experiments on Chevron Nozzles with Enhanced Momentum Thrust using Streamtube Expansion Waves

Noise regulations around the airport and rocket launching stations due to the environmental concern have made jet noise a crucial problem in the present day aeroacoustics research aiming to mitigate the undesirable jarring sound to avoid health hazards. The present paper is a continuation of our previous connected paper (AIAA 2019-4070). In this manuscript comprehensive in silico and in vitro studies on the jet acoustic characterization of chevron nozzles for its geometry optimization have been carried out. In silico studies have been carried out using validated steady 3d, double precision, density-based implicit, SST k-ɷ turbulence model with heat transfer effect. In this study, the fully implicit finite volume scheme of compressible, Navier–Stokes equations are employed. As a part of the code verification and calibration the numerically predicted 3d boundary layer blockage at the Sanal flow choking conditions for a channel flow is verified with the closed form analytical model (V.R.S.Kumar et al., Nature Scientific Reports, 2021) and found good agreement with the benchmark data. Comprehensive in silico and in vitro experiments reveal that the suitable selection of the number of lobes in a chevron nozzle with aerodynamically designed tapered tip creating streamtube expansion wave is a meaningful objective for achieving the jet noise reduction coupled with enhanced momentum thrust to the aircraft and rockets. In our case study, we found that the chevron lobes facilitated with tapered-tip with 80 angle could enhance the momentum thrust by 6 % and reduce the acoustic power level by 5 % while comparing with the base model. We concluded that the chevron cap with tapered tip creating streamtube expansion waves (V.R.S.Kumar et al., Physics of Fluids, 2021, doi: 10.1063/5.0040440) at the exit of the chevron nozzle is a profitable option for attenuation of the acoustic power level with momentum thrust benefits. This paper is a pointer towards for the geometry optimization of environmental friendly chevron nozzles with tapered tip for generating streamtube expansion waves for improving the momentum thrust while attenuating the acoustic power level for the future orbital and sub-orbital launch vehicle applications without sacrificing the mission demanding thrust-time requirements.