Ph.D. Proposal Presentation by Fahd Abdelall
Wednesday, June 11, 2003

(Drs. Said Abdel-Khalik and Minami Yoda, co-advisors)

"Experimental and Numerical Studies of the Rayleigh-Taylor Instability for Bounded Liquid Films with Injection through the Boundary"

Abstract

One of the most demanding engineering issues in Inertial Fusion Energy (IFE) reactors is the design of a reaction chamber that can withstand the intense photons, neutrons and charged particles due to the fusion event. Rapid pulsed deposition of energy within thin surface layers of the fusion reactor components such as the first wall may cause severe surface erosion due to ablation. One particularly innovative concept for the protection of IFE reactor cavity first walls from the direct energy deposition associated with soft X-rays and target debris is the thin liquid film protection scheme. In this concept, a thin film of molten liquid lead is fed through a porous silicon carbide first wall to protect it from the incident irradiations.

Numerous studies have been reported in the literature on the thermal response of the liquid film to the intermittent photon and ion irradiations, as well as on the fluid dynamics and stability of liquid films on vertical and upward-facing inclined surfaces. However, no investigation has heretofore been reported on the stability of thin liquid films on downward-facing solid surfaces with liquid injection through (i.e. normal to the surface of) the porous wall. This flow models the injection of molten liquid lead over the upper end cap of the reactor chamber. The hydrodynamics of this flow can be interpreted as a variation of the Rayleigh-Taylor instability due to the effect of the bounding porous wall which is continuously fed with the heavier fluid.

In order to gain additional insight into the thin liquid film protection scheme, experiments are proposed that investigate the critical issues associated with this concept. To this end, an experimental test facility will be designed and constructed to simulate the hydrodynamics of thin liquid films injected normal to the surface of and through downward-facing flat porous walls. The objective of this doctoral thesis is to determine the effect of different design parameters (film thickness, liquid injection velocity, liquid properties and inclination angle) on the liquid film and its stability. The results will address the morphology of the film free surface, the frequency of droplet formation and detachment, and the size and penetration depth of the detached droplets. These experimental data will be used to validate an existing numerical code based on a level contour reconstruction front tracking method over a wide range of parameters.

The results of this investigation will allow designers of IFE power plants to identify appropriate “windows” for successful operation of the porous wall protection concept for different coolants.