Interface node behavior due to nonlinearities in a 2D Rayleigh-Taylor instability
Résumé
We report a quantitative study on the symmetry effect of nonlinearities in a typical Rayleigh-Taylor (RT) instability for a single-mode sinusoidal initial perturbation. We use the interface zero-crossings (nodes) to monitor the asymmetrical deformation of the interface due to the growth of non-linear odd harmonics. A weakly nonlinear model is developed and compared to measurements of node positions in fourteen RT experiments performed using the magnetic levitation technique. Our results suggest that monitoring the nodes' spatial displacement over time is a powerful technique for detecting the first nonlinear harmonic, and more broadly, exploring the transitional regime between linearity and fully-developed nonlinearity. The nodes approach provides a metric complementary to the deformation amplitude, which is widely used to measure the amplitude effect of nonlinearities in most interface instabilities.