2008 Volume 3 Issue 5 Pages 701-711
The analytical model developed in the previous paper is applied to excitation of an axisymmetric fundamental wave on a fluid-fluid interface enclosed by a vertical cylinder. The excitation is caused by a forced vertical motion of the fluids relative to the stationary solid wall. Model analyses reproduced experimental results on the interface wave amplitude and phase relationship to the forced excitation. It is found that the deformation of the interface, that is primary mechanism exciting the wave, takes place only in a part of each cycle. In this time period the interface is hinged directly to the fluid-fluid-wall contact line of low mobility and hence the near-wall interface profile is subjected to deformation as a result of the forced fluid motion relative to the wall. For the rest of the cycle the interface is virtually untied from the wall due to the presence of a liquid film between the moving interface and the contact line, which can stretch or shrink without imposing additional forces on the moving interface. The fraction of the time period when the interface is hinged on the wall without intervention by the liquid film decreases as the excitation amplitude is increased, or the wave amplitude increases. The effective, cycle-averaged mobility of the interface, dependent on this time fraction, affects the natural frequency of the interface as well as the efficiency of wave excitation.
