Accession Number : ADA138999

Title :   Experimental Observations of Vortex Ring Interaction with the Fluid Adjacent to a Surface.

Descriptive Note : Interim rept.,


Personal Author(s) : Cerra,A W , Jr ; Smith,C R

PDF Url : ADA138999

Report Date : Oct 1983

Pagination or Media Count : 189

Abstract : Experimental studies examined the breakdown of initially laminar vortex rings during impact with both solid and free surfaces in a quiescent environment, and with a solid surface beneath a developing laminar boundary layer. Flow interactions were visualized in water using dye and hydrogen-bubble techniques and recorded with a high-speed video system. When a vortex ring approaches a surface the resulting flow interaction appears to be chaotic and turbulent, but is actually a very organized viscid-inviscid process which rapidly disperses the vorticity of the vortex ring throughout the surrounding fluid. Described is the flow interaction which integrates the following phenomena: (1) generation of secondary vorticity of opposite sense to that of the vortex ring; (2) deviations in the trajectory of the vortex ring from that predicted by classical theory; and (3) the processes of organized dispersal of vorticity. The process by which vorticity dispersal occurs is dependent upon the initial Reynolds number (Re sub 0) of the vortex ring. For very weak rings, i.e. Re sub o less than 350, vorticity is dispersed by laminar diffusion. For stronger rings, vorticity dispersal occurs discretely through formation of secondary and tertiary vortex rings (SVR and TVR) via a viscous boundary layer process. Vorticity dispersal continues as a result of Biot-Savart-type interactions of the SVR and TVR with the original or primary vortex ring. During this interaction the diameter of the SVR is compressed, causing an instability in the SVR which is characterized by an azimuthal waviness.

Descriptors :   *Vortices, *Boundary layer, *Laminar flow, Rings, Impact, Surfaces, Interactions, Laminar boundary layer, Viscous flow, Inviscid flow, Secondary flow, Dispersing, Deformation, Circulation, Waves, Reynolds number, Water flow, Flow visualization, Dyes, Bubbles, Hydrogen, High speed photography, Water tunnels

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE