Experimental Study of the Incompressible Richtmyer-Meshkov Instability

Incompressible Richtmyer-Meshkov instability (RMI) experiments are conducted using miscible and immiscible fluid pairs with matched viscosity and Atwood number (A = 0.22).  Dioctyl sulfosuccinate sodium salt (AOT) surfactant is added to the immiscible pair.  Forced and unforced initial perturbations are examined.  Initially stably stratified fluid pairs are accelerated in the destabilizing direction using an 8 meter linear induction motor drop tower for a duration of 100 ms.  RMI occurs when the fluid pairs enter free fall following this initial acceleration.  Mixing between the two fluids is visualized using planar laser induced fluorescence (PLIF) with images captured by a high speed camera.  Time dependent mixing region widths for both miscible and immiscible fluid pairs are obtained from the PLIF image sequences.  Mixing region behaviors for both fluid combinations are compared. 

Time-dependent interfacial tension measurements are also conducted in order to examine the effects of AOT surfactant on the immiscible fluid pair.  Interfacial tension measurements are obtained from pendant drop tensiometry.  Measurements of varying drop sizes and durations are compared to structure sizes and times observed in the RMI experiments.