Miscible Rayleigh-Taylor Instability Experiments on the Linear Induction Motor (LIM) 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 10.5g. 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 445nm wavelength laser sheet. Variation of the indices of refraction (IOR) of the two fluids occurs during mixing, producing image blurriness and negatively affecting PLIF Imaging. This IOR variation is minimized by modeling the IOR of the fluids as a nonlinear fluid property, allowing preparation of optimized fluid pairs. Both unforced and forced experiments are performed. Forced experiments are conducted to produce initial perturbations and capture more of the RTI growth within the experimental observation window. Measurements of the resulting mixing layer growth and growth rates will be presented.