Simultaneous Velocity and Concentration Measurements of a Twice-Shocked Mixing Layer*

The twice-shocked Richtmyer-Meshkov instability is investigated in the vertical shock tube of the Wisconsin Shock Tube Laboratory at the University of Wisconsin–Madison. The initial condition is a shear layer, containing broadband perturbations, formed at the interface between a Helium-Acetone mixture and Argon.

The interface is accelerated with a shock of nominal strength M=1.9 with an initial Atwood number of A=0.43. The evolution of the interface is investigated at 4 distinct post-reshock times.

Acetone is used as a molecular tracer for PLIF, allowing the extraction of concentration data, while the interface and the regions above and below it are seeded with titanium dioxide particles, to allow the use of PIV to measure 2-D velocity fields.

Turbulence is investigated using the measured velocity and concentration fields which are analyzed via energy spectra, structure functions, and PDFs. Integral parameters such as interface thickness and degree of mixedness are evaluated as well as the Reynolds stresses, the Taylor microscale, and the internal and external Reynolds numbers.