Interaction of an obliquely rising vortex ring with a free surface in a viscous fluid

Meccanica ◽  
1996 ◽  
Vol 31 (6) ◽  
pp. 623-655 ◽  
Author(s):  
Samuel Ohring ◽  
Hans J. Lugt
Keyword(s):  
Free Surface ◽  
Viscous Fluid ◽  
Vortex Ring

The mechanism of vortex connection at a free surface

1999 ◽  
Vol 384 ◽  
pp. 207-241 ◽  
Author(s):  
CHIONG ZHANG ◽  
LIAN SHEN ◽  
DICK K. P. YUE
Keyword(s):  
Free Surface ◽  
Boundary Conditions ◽  
Vortex Ring ◽  
Stokes Equations ◽  
Incidence Angle ◽  
Surface Boundary ◽  
Viscous Layer ◽  
Vertical Vorticity ◽  
Vorticity Component ◽  
Stress Boundary Conditions

Vortex connections at the surface are fundamental and prominent features in free-surface vortical flows. To understand the detailed mechanism of such connection, we consider, as a canonical problem, the laminar vortex connections at a free surface when an oblique vortex ring impinges upon that surface. We perform numerical simulations of the Navier–Stokes equations with viscous free-surface boundary conditions. It is found that the key to understanding the mechanism of vortex connection at a free surface is the surface layers: a viscous layer resulting from the dynamic zero-stress boundary conditions at the free surface, and a thicker blockage layer which is due to the kinematic boundary condition at the surface. In the blockage layer, the vertical vorticity component increases due to vortex stretching and vortex turning (from the transverse vorticity component). The vertical vorticity is then transported to the free surface through viscous diffusion and vortex stretching in the viscous layer leading to increased surface-normal vorticity. These mechanisms take place at the aft-shoulder regions of the vortex ring. Connection at the free surface is different from that at a free-slip wall owing to the generation of surface secondary vorticity. We study the components of this surface vorticity in detail and find that the presence of a free surface accelerates the connection process. We investigate the connection time scale and its dependence on initial incidence angle, Froude and Reynolds numbers. It is found that a criterion based on the streamline topology provides a precise definition for connection time, and may be preferred over existing definitions, e.g. those based on free-surface elevation or net circulation.

Experimental Study of Ship Response due to Internal Viscous Cargo Motions

2018 ◽  
Author(s):  
Virginie Baudry ◽  
Jean-Marc Rousset
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Viscous Fluid ◽  
Fresh Water ◽  
Iron Ore ◽  
Experimental Approach ◽  
Viscous Fluids ◽  
Maritime Industry ◽  
Bulk Carrier ◽  
Ship Model

Potential liquefaction of some cargoes (Nickel ore, iron ore, ...) is a major risk for the maritime industry. The difficulties to simulate accurately the behaviour of these materials as well as their interaction with a bulk carrier model leaded us to use a non-Newtonian highly viscous fluid to model a liquefied ore. An experimental approach is presented in this paper. Roll responses of a ship model as well as details on the internal free surface behaviours are investigated for different loading conditions: solid cargo, fresh water and viscous fluids.

Axisymmetric interaction between a vortex ring and a free surface

1994 ◽  
Vol 6 (1) ◽  
pp. 224-238 ◽  
Author(s):  
Peder A. Tyvand ◽  
Touvia Miloh
Keyword(s):  
Free Surface ◽  
Vortex Ring
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