Drop-formed vortex rings—The generation of vorticity

• DOI: 10.1063/1.868524
• Publication Date: 2002-07-26T12:09:39Z
• Authors: R. W. Cresswell; B. R. Morton
• Keywords: Vortex stretching; Burgers vortex; Coalescence (physics); Vortex sheet

Vortex rings are seen to form when dyed water drops strike a surface and their formation structure depend on height of fall tension. The assumption that vortex sheet envelopes the penetrating drop, frequently stated without explanation in literature, does not explain these factors this paper shows why it is incorrect. Alternative mechanisms have been proposed literature but none explains adequately vorticity generation or restriction ring low Weber numbers. This proposes mechanism based relaxation stresses at coalescence. condition viscous stress be continuous across water-air interface leads boundary total amount generated depends quantity which can diffused into fluid interior from during At values number appears sufficient generate enough allow flow separation surface, such being necessary for roll-up production. existence critical above do result balance between rate contact moves outward associated with one hand, action tension forces and, other, destruction due coming together surfaces. If dominates then elements applies will become part before diffusion has carried significant away surface.