RESEARCH ARTICLE Experimental investigation of liquid jet injection into Mach 6 hypersonic crossflow

Abstract The injection of a liquid jet into a crossing Mach 6 air flow is investigated. Experiments were con-ducted on a sharp leading edge flat plate with flush mounted injectors. Water jets were introduced through different nozzle shapes at relevant jet-to-air momentum– flux ratios. Sufficient temporal resolution to capture small scale effects was obtained by high-speed recording, while directional illumination allowed variation in field of view. Shock pattern and flow topology were visualized by Schlieren-technique. Correlations are proposed on relating water jet penetration height and lateral extension with the injection ratio and orifice diameter for circular injector jets. Penetration height and lateral extension are compared for different injector shapes at relevant jet-to-air momentum– flux ratios showing that penetration height and lateral extension decrease and increase, respectively, with injec-tor’s aspect ratio. Probability density function analysis has shown that the mixing of the jet with the crossflow is completed at a distance of x/dj * 40, independent of the momentum–flux ratio. Mean velocity profiles related with the liquid jet have been extracted by means of an ensemble correlation PIV algorithm. Finally, frequency analyses of the jet breakup and fluctuating shock pattern are performed using a Fast Fourier algorithm and characteristic Strouhal numbers of St = 0.18 for the liquid jet breakup and of St = 0.011 for the separation shock fluctuation are obtained. List of symbols Aj area of injected jet orifice (