VISCOUS EVOLUTION OF 2D DIPOLAR VORTICES

Numerical simulations with a finite-difference method have revealed th at a Lamb dipole when placed in a viscous fluid moves along a straight line with decreasing velocity and increasing radius. The relationship between vorticity and streamfunction, which initially is linear, beco mes more and more sinh-like as the dipole decays. Some other initial d ipolar vorticity distributions (like two oppositely signed monopolar v ortices) were found to evolve to a dipolar structure with Lamb-like ch aracteristics. (C) 1998 The Japan Society of Fluid Mechanics Incorpora ted and Elsevier Science B.V. All rights reserved.