Fluid Instabilities in Different Conditions

Interfacial fluid instabilities are one of the open challenges to the scientists and researchers of fusion community and Astrophysicists. The most common fluid instabilities are RayleighTaylor (RTI), Richtmyer-Meshkov (RMI), Kelvin-Helmholtz (KHI) according to the name of the discoverers. However, these instabilities arise at the interface of two fluids under different physical conditions. RTI occurs when a density gradient ( ~ ) is subjected to an acceleration by an antiparallel pressure gradient ( ~ P) in the presence of perturbations, i.e., when ~ · ~ P 0. This occurs, for example, when a dense fluid is placed above a less dense fluid in the presence of gravity (or in constant force) and then falls when the interface is perturbed. The RTI develops in three stages, beginning with an exponential growth in which each perturbation mode develops independently and is well described by linear stability theory. When the mode amplitude becomes comparable to its wavelength, nonlinearities cause the growth rate to decline, with bubbles of less dense fluid rising parallel to ( ~ ) and separated by narrower spikes of denser fluid traveling in the opposite direction.