DAMPED OSCILLATIONS OF A LIQUID GAS SURFACE UPON STEP REDUCTION IN GRAVITY/

The reorientation and settling of a liquid/gas interface in a right ci rcular cylinder upon step reduction in gravity is investigated numeric ally. A modified dynamic contact angle boundary condition is implement ed where the hysteresis parameter gamma is employed as an adjustable p arameter representing the degree of relative slip at the contact line. The effect of the boundary condition on the axial interface oscillati on is studied and the dependence thereon of the resonant frequency and settling time is given. Results are shown regarding the behavior of t he dynamic contact angle and the penetration of the surface oscillatio ns into the bulk liquid. The numerical results are tuned via compariso ns with existing experimental data, and a method for estimating the ap propriate boundary condition providing good agreement is suggested. An accompanying scale analysis depicts gamma as a function of the Ohneso rge number, the cylinder radius, and the static contact angle, These i ndependent parameters are measures of the system damping, characterist ic surface deflection, and effective stiffness of the interface, Appli cations of the results may be made to spacecraft fluids management and the use of spacecraft and/or drop towers for fluids experimentation.