[CIG-LONG] Static vs. Wrap Top, Hydrostatic Top BC, Static Left Boundary

[Karen Paczkowski]

Hi,

I am having difficulty with the static vs. wrap top boundary setting,  
the hydrostatic top BC, and a static side boundary setting.  I am  
trying to simulate a vertical subduction zone, so that the velocity  
along the left edge is Vy = -Vslab and Vx=0.  I would like to keep the  
top of the simulation flat, so Vy=0 and the left and bottom just a  
hydrostatic pressure condition (as to simulate an infinite domain).

I am having two issues, one with the top surface and one with the left  
side.


A)  Top surface:  I am not sure whether to set a static or a wrap  
top?  or if it will make a difference?  I am also not sure if I should  
set a hydrostatic top boundary condition?  I would like material to  
flow in and out of the simulation when the hydrostatic pressure  
gradient is disturbed, which would make me believe that i should, but  
I am setting Vy=0 at the top which would make me believe I don't need  
to?

I have tried using:
1) Hydrostatic top BC with a Wrap top
2) Hydrostatic top BC with a Static top
3) No hydrostatic top BC with a Static top.

I found that all 3 cases start with the same velocity field.  Then as  
time progresses 2 and 3 continue to produce identical velocity fields,  
but that 1's velocity field is different.  This makes me believe that  
the difference between a static and wrap top matters.  Since I have  
set Vy=0 at the top I was surprised that static and wrap top made a  
difference.  What does setting static top do exactly?  Is it different  
than setting Vy=0?  I have noticed that case 2 and 3 seem to be  
timestepping the same as each other, but 1 is timestepping different,  
so this may be the reason for the discrepency.

Can someone please explain the difference between static and wrap top  
if Vy=0 at the top?  Does it matter which one is set and if so which  
one is more appropriate?

Also does adding a hydrostatic top BC matter if Vy=0 at the top?  Does  
having the hydrostatic term in there affect the simulation?  I have  
attached my xml file for the hydrostatic top BC and a static top.


B)  Left side:  I have the left side of the simulation set to Vy = - 
Vslab and Vx=0.  I have set leftside to Static but I am not sure if  
this should be done.  I thought it should based off of the cookbook  
inflow example, but am not sure.  Setting leftside static creates a  
very funny shaped simulation box where the left side is offset under  
the rest of the simulation box.  I have attached a picture of the  
simulation box.  Does setting leftside Static constrain that side of  
the simulation too much?  Should I remove it?


Thank you,
Karen

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