[MITgcm-support] Specify W velocity with OBCS?

[Matthew Mazloff]

Hi David,

It is just a nice feature of the c-grid and obcs implementation that  
I really think the W and P in the center point of the obcs does not  
effect the interior in the hydrostatic mode.  If you are using non- 
hydrostatic and have terms like Wxx this may become an issue...and as  
the MITgcm currently does not have the capability of prescribing W  
you could either
1) carefully choose tangential velocity so W get is what you want
2) implement the code so that W is overwritten after it is solved for  
by divergence of tangential velocity
3) use sponge layers to limit effect of whatever is happening right  
on the boundary


good luck
Matt

ps> Not sure what you mean by a "swirl", maybe someone else can help  
you with that.


On Jan 14, 2008, at 2:17 PM, David Hebert wrote:

> Hi Matt,
>
> Thanks for your response. I can see that  a point on a boundary  
> wouldn't be solved for since it is specified, but wouldn't it  
> affect the adjacent interior point somehow? I probably should note  
> that I am using the model in non-hydrostatic mode.
>
> My previous question stems from wanting to specify a jet on the  
> boundary. Implementing a "Top Hat" jet on the west boundary using  
> OBWuFile seems to work. If I wanted to model a jet with swirl I was  
> thinking I would specify all three velocity components on the  
> boundary. A Google search for 'MITgcm OBWwFile' gives a few hits,  
> so I thought it would be possible to specify vertical velocity on  
> the boundary.  Perhaps this was possible in the past? If not, it  
> looks like something I will have to add to the code.
>
> As m. schaferkotter noted, the namelist in MITgcm/pkg/obcs/ 
> obcs_readparms.F does not have any W velocity boundary files.
>
> Thanks,
>
> David
>
> Matthew Mazloff wrote:
>> Hi David,
>>
>> I do not believe W (and P) on the open boundary comes into the  
>> dynamics.  If W on this point is solved for (and thus given as  
>> output) it will be because there is some divergence in the  
>> prescribed tangential velocity....but this doesn't effect the  
>> interior.
>>
>> -Matt
>>
>>
>> On Jan 14, 2008, at 11:06 AM, David Hebert wrote:
>>
>>> All,
>>>
>>> Is there a way so specify W velocity using OBCS and EXF? When I  
>>> specify 'OBWwFile = w.bin' in data.obcs, I get an error saying it  
>>> is not found in namelist:
>>>
>>> PGFIO-F-239/namelist read/unit=11/entity name is not member of  
>>> group.
>>> File name = /tmp/FTNwcP5jg7mUsXg8    formatted, sequential  
>>> access   record = 17
>>> In source file obcs_readparms.f, at line number 1989
>>>
>>> Thanks,
>>>
>>> David
>>>
>>>
>>> _______________________________________________
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>>
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