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This study reports the development and characterization of amultiple-supersonic-jet wind tunnel designed to investigate the decay of nearlyhomogeneous and isotropic turbulence in a compressible regime. The interactionof 36 supersonic jets generates turbulence that decays in the streamwisedirection. The velocity field is measured with particle image velocimetry byseeding tracer particles with ethanol condensation. Various velocity statisticsare evaluated to diagnose decaying turbulence generated by the supersonic jetinteraction. The flow is initially inhomogeneous and anisotropic and possessesintermittent large-scale velocity fluctuations. The flow evolves into astatistically homogeneous and isotropic state as the mean velocity profilebecomes uniform. In the nearly homogeneous and isotropic region, the ratio ofroot-mean-squared velocity fluctuations in the streamwise and verticaldirections is about 1.08, the longitudinal integral scales are also similar inthese directions, and the large-scale intermittency becomes insignificant. Theturbulent kinetic energy per unit mass decays according to a power law with anexponent of about 2, larger than those reported for incompressible gridturbulence. The energy spectra in the inertial subrange agree well with otherturbulent flows when normalized by the dissipation rate and kinematicviscosity. The non-dimensional dissipation rate is within a range of0.51--0.87, which is also consistent with incompressible grid turbulence. Theseresults demonstrate that the multiple-supersonic-jet wind tunnel is helpful inthe investigation of decaying homogeneous isotropic turbulence whose generationprocess is strongly influenced by fluid compressibility.

Nearly homogeneous and isotropic turbulence generated by the interaction of supersonic jets