An Experimental Investigation of the Stability of a Thin Liquid Layer Adjacent to a Supersonic Stream

Abstract

The experiments to study the interface response of a liquid film with a concurrent supersonic airflow were conducted at freestream Mach numbers of 4.95 and 7.3 with stagnation pressures of 3.4, 6.8, and 17.0 atm. A sphere-cone and a blunt wedge were used as test configurations. The liquid layer Reynolds number jR, based on interface velocity and liquid depth, ranged from approximately 0.3 to 300.0 as the thickness ranged independently from 0.01 to 0.05 cm. The nondimensional wave speed was found to decrease monotonically with increasing R from a value greater than the interface velocity (fast waves) to a value lower than the interface velocity (slow waves). The transition from fast waves to slow waves appeared to occur at a Reynolds number near 100. The dependence of wavelength and wave speed on Reynolds number, shear stress, Mach number, and depth are given. In the small Reynolds number range, the results are compared with a long wave analysis to show the destabilizing effects of Reynolds number and shear stress. In the high Reynolds number range, the results are compared with an analysis based on a Tollmien-Schlichting instability mechanism.