Miscible Experiments on the Rayleigh-Taylor Instability in the Linear Induction Motor Drop Tower

Incompressible, miscible experiments on the Rayleigh-Taylor Instability (RTI) using Planar Laser Induced Fluorescence (PLIF) imaging are presented. A vertical tower guides a test sled that is accelerated downward using linear induction motors. Experimental liquid pairs are prepared and placed into a test chamber attached to the sled. The sled is accelerated at a rate of approximately 15g. Upon acceleration, the stratified initially stable fluid pair within the chamber becomes unstable causing the development of RTI. The resulting RTI is imaged using PLIF by seeding the heavier fluid with fluorescein dye that is illuminated by a scanning 445nm wavelength laser beam. The indices of refraction (IOR) for the two liquids are initially matched prior to tank filling. However, the mixing of the fluids produced by RTI development alters the IOR. Variation of IOR within the fluids produces image blurring, negatively impacting PLIF imaging. Variation of IOR is minimized by modelling as a nonlinear fluid property, allowing preparation of optimized fluid pairs that reduce image blurriness. Measurements of the resulting mixing layer growth will be presented.