[Mitgcm-support] .

[mitgcm-support at dev.mitgcm.org]

The e-mail below is that I wrote one week ago and your answer about using 
Crank-Nicholson time stepping was sucessfull but I can't understand why 
there are different behaviours if I impose different boundary conditions in 
a situation without any dissipation factor.

Thank you again
Fabiana Cavazzon

Dear Sir

I'm studying the code by using the exemples and modifying them but I have 
some problems about boundary-conditions.
As regards exp0 I changed the topography and I fixed initial condition on 
eta by pSurfInitFile. Eta at time=0 has linear variation only on x direction 
(eta=a*x+b).Besides I imposed no_slip_sides and no_slip_bottom FALSE and 
viscAh=0 and there are not external forces.
So I thought to obtain a free oscillation of the surface but it wasn't so: 
there is a dissipation and the oscillation is dependent on the topography. 
It's different if I use one or more walls (for expample     h(:,end)=5 or on 
other sides) at the boundaries and it changes with the position of the 
walls.
I tried to understand the reason of the different behaviour but I couldn't 
find why the way of oscillating changes and why its amplitude goes down if 
there are not dissipation factors.
In exp0 ALLOW_OBCS is undef and is imposed h(:,end)=0 and h(end,:)=0.

Thanks in advance for helping me and I hope to have been clear enough.

Fabiana Cavazzon
OGS-Trieste Italy


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