VORTEX RING GENERATION DUE TO THE COALESCENCE OF A WATER DROP AT A FREE-SURFACE

Results are presented of an experimental investigation of vortex ring formation by a fluid drop contacting a free surface with negligible ve locity. The pool fluid is mixed with fluorescein dye, and a laser shee t is used to illuminate a plane of the flow. A series of representativ e images is recorded by a CCD camera and speculation is made regarding specific sources of vorticity flux through the free surface. Two scal ing analyses previously presented by other investigators are demonstra ted to be equivalent under the assumptions of this experiment, and the y provide the motivation for a series of test runs in which the durati on of the coalescence process, tau, is related to variations in drop diameter L and fluid surface tension a. Experimental results are in ag reement with the analyses, showing tausimilar to sigma(-1/2) and tau* similar to L(3/2).