ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

4pPA11. Capillary bridge stability in an acoustic standing wave: Linearized analysis of passive stabilization with radiation pressure.

Philip L. Marston

Dept. of Phys., Washington State Univ., Pullman, WA 99164-2814

A liquid bridge between two solid surfaces, known as a capillary bridge, has applications in low gravity such as the solidification of floating zones. Long bridges are naturally unstable to a symmetric mode where a region adjacent to one end bulges while the opposite end thins. For a cylindrical bridge of radius R and length L, the slenderness S=L/2R has a natural (Rayleigh) limit of (pi) beyond which the bridge breaks. It is proposed here to stabilize dense bridges at a velocity antinode of a standing acoustic wave perpendicular to the bridge axis. Let denote the angular average of the radiation pressure over the surface of a cylindrical bridge. It is necessary to select the acoustic frequency such that increases with R so that a bulge is automatically squeezed by the increased radiation pressure. Linearized analysis of the stability indicates S may be extended beyond (pi): S[sub max] depends on q=(R[sup 2]/(gamma))d/dR, where (gamma) is the surface tension and S[sub max] diverges as q approaches unity. The analysis supports the possibility of passive acoustic stabilization of capillary breakup in low gravity. The one-dimensional inviscid slice approximation is used in the analysis of axisymmetric deformations. [Work supported by NASA.]