## Collision under 90 degrees of two Lamb dipoles

*Details on the computation and presentation*

**Initialisation**
Dipoles: both dipoles:
velocity: U = 2; maximum initial vorticity 22.1
radius: a = 1
dipole 1:
position: (-3.5,0)
angle of dipole axis with X-axis: 0 degrees
dipole 2:
position: (0,+3.5)
angle of dipole axis with X-axis: -90 degrees
Computation: domain: X = (-5, ..., 3), Y = (-5, ..., 5)
no. of grid points from wall to wall: (129, 129)
boundary conditions: stress-free along all walls
standard Arakawa scheme used
no rotation effects included
no bottom topography
viscosity: nu = 10^-3 (i.e. Re=1000 at T=0)
time step: dt = 0.01
final time: T = 4
Tracers: along vorticity contours (i.e. along streamlines)
of both Lamb dipoles at vorticity levels: 0.1, 6.0,
12.0, 18.0; and a single tracers at each extremum
**Note**
The tracer lines are not always smooth. The reason for this
is that the representation of the lines by points is not always
accurate enough. But since these tracers only passively follow
the flow, this has no effect on the computations.
It needs repair, though.

<=== Collision under 90 degrees of two Lamb dipoles

**
Jos van Geffen** --
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###### created: 4 November 1996

last modified: 26 May 2001