Towards pressure-velocity-density correlation measurements in variable-density mixing

Variable-density (VD) flows are encountered in compressible flows, e.g., explosions, or in incompressible flows, when two fluids with different density mix. There has never been an experimental dataset capable of completely verifying VD turbulence modeling because it requires simultaneous 3D velocity, density, and pressure measurements. Typically, the experimental validation of the corresponding VD turbulence models is incomplete: parts of these models are directly inherited from analogous constant-density turbulence modeling. This work presents a series of high-speed stereoscopic-PIV and PLIF measurements in a variable-density jet. The measurement plane is shifted through the first developing region of the jet flows, where VD effects on the turbulence mixing are the most relevant, thus providing a 3D evolution of turbulent statistics. In conjunction with this diagnostic strategy, the time-correlation information embedded into the high-speed density and velocity measurements is used for inferring the local, full 3D structure of density and velocity by means of a modified version of the Taylor’s hypothesis of frozen turbulence, which finally enables computation of pressure fields and, consequently, of the pressure-velocity-density correlations.