Superciritical fluids may be regarded as intermediate between liquid and gas exhibiting high liquid like density and low gas like viscosity. These fluids exist beyond the liquid-vapor critical point where there the boundary between liquid and gas does not exist. The demand for supercritical fluids has escalated over the past several decades in diverse industrial applications, efficient refrigeration systems, drilling technologies and in high performance rocket propellants [Shen and Zhang, 2013]. This is attributed to the emergence of some atypical thermo-physical properties as one approaches the critical point such as the divergence of the constant-pressure specific heat capacity and compressibility [Shen and Zhang, 2013]. When these fluids are acted upon by longitudinal vibrations, the coupling between thermal boundary layer and longitudinal accelerations lead to onset of instability of thermal boundary layer which is largely governed by the distance from critical point. In experimental study aboard sounding rocket, emergence of fingers depicting destabilization of thermal boundary was observed wherein super-critical CO_2 was subjected to vibrations under weightlessness. Numerical studies pertaining to supercritical fluids subjected to vibrations were initially performed by [Amiroudine and Beysens, 2008] who observed the fingering structure in the thermal boundary layers with different proximities to the critical point. Similar results were also reported when supercritical hydrogen was subjected to longitudinal vibrations in the numerical studies of [Gandikota et al., 2013]. They evaluated the effect of vibrations using three different combinations of boundary conditions thus providing insight into the mechanisms of corner, parametric and Rayleigh vibrational instability.
展开▼
