For two decades, the IUSTI laboratory, in collaboration with CEA/DAM/DIF, investigates the Richtmyer-Meshkov instability (RMI) from planar experiments performed in a horizontal shock tube. In the present work, we propose to experimentally study the interaction of an initially perturbed gaseous interface with a cylindrical converging shock wave still using a conventional shock tube but with a specifically designed test section, in which the incident planar shock wave is directly converted into a cylindrical one. This can be done when the incident shock wave crosses an adequately shaped interface between two gases with a suitable impedance mismatch to curve into in a cylindrical transmitted shock wave. During the last symposium [1], we have successfully validated the concept of the gas lens [2,3] to convert a planar shock wave of Mach number 1.15 into a cylindrical one, through an air/SF6 elliptic interface, while keeping the flexibility of a classical shock tube. The ultimate stage is now achieved with the addition of a second perturbed SF6/air interface whose the post-shock evolution is captured with a high speed camera combined with Schlieren technique and analysed from pressure histories recorded a different stations of the device. Figure 1 gives a schematic and a picture of the test section which can directly convert an incident planar shock wave into a cylindrical one that destabilizes of a perturbed interface.
Figure 1: Schematic and view of the test section
As shown in Figure 2, we will present the results obtained with this approach and exhibit the great potential of this experimental method for the Richtmyer-Meshkov instability study induced by focusing shock waves.
Figure 2: Example of Schlieren pictures showing the evolution of the Richtmyer-Meshkov instability induced at a SF6/air perturbed interface by a converging cylindrical shock wave created from a Mis=1.15 planar shock wave issued from a conventional shock tube through an air/SF6 gas lens.
[1] L. Biamino, G. Jourdan, C. Mariani, L. Houas, M. Vandenboomgaerde and D. Souffland, “Generation of cylindrical converging shock waves in a conventional shock tube“, ISSW29, Madison, Wisconsin, United States (2013).
[2] P. E. Dimotakis and R. Samtaney, “Planar Shock Cylindrical Focusing by a Perfect-Gas Lens,” Phys. Fluid., 18(3), pp. 031705–031708, (2006).
[3] M. Vandenboomgaerde and C. Aymard , “Analytical theory for planar shock focusing through perfect gas lens and shock tube experiments designs “, Physics of Fluids, 18, 031705 (2011).
