Experiments and Numerical Simulations on the Mid-Term Evolution of Hypersonic Jets
The experiment described here is focussed to the observation of underexpanded, hypersonic turbulent jets. The experiment is relevant to a few aspects concerning the dynamics of astrophysical phenomena such as the Herbig-Haro jets and to the interaction between the large-scale vortices and the system of shocks that determine the spreading and entrainment properties of highly compressible free-flows. A number of orifice jets with a ratio between the stagnation pressure and the ambient pressure of the order 103–104 have been studied by changing the stagnation/ambient density ratio. This has been realized using dissimilar gases in the jet and in the ambient medium: by using He, Ar and air the stagnation/ambient density ratio can be changed by one order of magnitude while keeping fixed the pressure ratio. It has been possible to visualize the near and mid-term evolution of the jets and measure the axial and transversal density distributions. A comparison relevant to the shock waves configuration in between the nozzle exit and the first Mach’s disk is shown for an air in air laboratory jet and its numerical simulation.
Keywordsastrophysical jet hypersonic jet compressible mixing entrainment
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