Nonlinear Evolution of the Rayleigh-Taylor and Richtmyer-Meshkov Instabilities

Scaled experiments on the nonlinear evolution of the RayleighTaylor (RT) and Richtmyer-Meshkov (RM) instabilities are described under a variety, of conditions that occur in nature. At high Reynolds number, the mixi,ng layer grows self-similarly aiAgt* for a constant acceleration (g), and as a power law t*’ 1 for impulsive accelerations US(t) at low and high Mach numbers. The growth coefficients oi and 8i exponents are measured over a comprehensive range of Atwood numbers A. The RT instability is also investigated with NonNewtonian materials which are independently characterized. A critical wavelength and amplitude for instability is observed associated with the shear modulus and tensile yield of the material. The results are applicable from supernova explosions to geophysical flows subject to these hydrodynamic instabilities. PACS numbers: 47.20.Bp, 47.25.Jn