Temperature rise and pressure dynamics in the early stages of Hartmann–Sprenger tube operation

Abstract In this study, we focus on the early stages of the Hartmann–Sprenger tube operation in the jet regurgitant mode to investigate three key relationships: (1) between the nozzle dynamic pressure and the start time of temperature rise at the resonance tube end, (2) between the nozzle dynamic pressure and the resonance tube end pressure, and (3) between the distance l from the resonance tube end to the contact surface and the rise in the end gas temperature of the resonance tube. The results showed that the condition for the rise in the resonance tube end gas temperature after the gas jet from the nozzle reached sonic flow was the stabilization of the average fluctuation pressure value at the resonance tube end in conjunction with the nozzle dynamic pressure. At the time of operation stabilization of the Hartmann–Sprenger tube, the average fluctuation pressure at the resonance tube end converged to a constant value almost equal to the nozzle dynamic pressure. This result means that the nozzle dynamic pressure is almost equivalent to the fluctuation pressure at the resonance tube end. Moreover, the distance l did not significantly increase with the resonance tube length L and remained nearly constant. The gas temperature at the resonance tube end obtained from the experimental results generally agreed with the temperature calculated from compression through an adiabatic and isentropic process from L to l .