[MITgcm-support] Re:How to reduce a reflection wave from OBCs!

Mon Apr 3 12:02:29 EDT 2006

Hi Pat

I just remembered I owe you some code too. You can get my internal  
tide code mods (used to
perform the simulations in the DSR paper) here: http:// 
www.ldeo.columbia.edu/~spk/internal_tides.tar.gz

After unpacking, you should find 2 directories: barotropic and  
baroclinic. The simulation procedure is
described here: http://www.ldeo.columbia.edu/~spk/Papers/ 
KhatiwalaInternalTidesDSR03.pdf

The code was written for checkpoint37, but should be usable with any  
recent version with only minor
mods.

Samar

On Apr 3, 2006, at 9:20 AM, Pat Gallacher wrote:

> Hi,
>
> I am having problems with internal waves reflecting off the open  
> boundaries in the MITgcm code. I'd appreciate a copy of your code  
> to address the problem.
>
> Thanks,
> Pat
>
> ------------------------------------------------------
> Patrick C. Gallacher, PhD    gallacher at nrlssc.navy.mil
> Oceanographer    Nonhydrostatic Coastal Ocean Modeling
> Naval Research Laboratory        Phone: (228) 688-5315
> Code 7331                    Secretary: (228) 688-4733
> Stennis Space Center, MS 39529     FAX: (228) 688-5997
> ------------------------------------------------------
>
>
>
> Samar Khatiwala wrote:
>
>> Hi
>>
>> Just to add to this discussion ... radiation BCs are definitely  
>> the  way to go. (As one of the
>> developers of the Orlanski package, I would of course say that.)  
>> But  its not foolproof. For the
>> barotropically forced internal wave problem, it took some serious   
>> effort to get the waves to
>> radiate out correctly (i.e., make it compare favorably with   
>> analytical solutions). This is documented
>> in a 2003 DSR paper on internal tide generation:
>> http://www.ldeo.columbia.edu/~spk/Papers/ 
>> KhatiwalaInternalTidesDSR03.pdf
>>
>> Last I looked, the basic orlanski code does not have the various   
>> hacks needed to radiate out
>> only the "baroclinic" component. It took some doing to get this   
>> right. If people don't want to reinvent
>> the wheel, I'll be happy to post this code somewhere. There is  
>> also  code to compute topographic
>> drag etc. (taking into account the lopped cell topo, subtracting  
>> out  the barotropic component, ...).
>>
>> Samar
>>
>> On Feb 11, 2006, at 12:46 PM, Jennifer MacKinnon wrote:
>>
>>> Hi,
>>>
>>> I've been struggling with similar issues regarding internal  
>>> waves  and boundary conditions.  My solution so far is to clamp  
>>> the  barotropic velocities to be whatever you like (a simple  
>>> sinusoid in  your case), but allow baroclinic velocities as well  
>>> as T and S to  radiate internal-waves out of the domain using the  
>>> Orlanski  radiation option.  This requires a little bit of  
>>> monkeying with  orlanski_west.F and orlanski_east.F, but is  
>>> fairly  straightforward.  Let me know if you'd like a copy of my  
>>> modified  files.
>>>
>>> Cheers,
>>>
>>> Jen
>>>
>>> ---------------------------------------------------------------
>>> Dr. Jennifer MacKinnon
>>> Physical Oceanography Research Division
>>> Scripps Institution of Oceanography
>>> http://www-pord.ucsd.edu/~jen/
>>> 858-822-3716
>>>
>>>
>>>>
>>>> From: Van Thinh Nguyen <vtnguyen at moisie.math.uwaterloo.ca>
>>>> Date: February 10, 2006 12:25:54 PM PST
>>>> To: mitgcm-support at mitgcm.org
>>>> Subject: [MITgcm-support] How to reduce a reflection wave from  
>>>> OBCs!
>>>> Reply-To: mitgcm-support at mitgcm.org
>>>>
>>>>
>>>> Dear all,
>>>>
>>>> I would like to simulate internal waves generated by tidal  
>>>> forcing  over a depression bump in a open channel (opened at  
>>>> east & west).  My case is similar to exp4, but it's limited in  
>>>> 2D. The tidal  current is from the East to West with u=Uo*sin 
>>>> (omega*t). At west  and east OBCs I set:
>>>>
>>>> OBWu=Uo*sin(omega*t)
>>>> OBWv=0.
>>>> OBWt=tRef
>>>> OBWs=sRef
>>>>
>>>> OBWw=0. for nonhydrostatic
>>>> OBWeta=Eta=0.
>>>>
>>>> At Eastern OBC is set the same above.
>>>>
>>>> I extended the length of domain from 60km, 120km, ...
>>>> the depth of domain H=80m (shallow), depth of bump=50%*H.
>>>>
>>>> I got refection waves from both OBCs, because Temperature  
>>>> profile  (linearized in depth) is fixed at these OBCs (always  
>>>> =tRef),  however the temperature profile in inner domain has  
>>>> changed.
>>>>
>>>> Anyone may have an idea to help me to fix this problem?
>>>>
>>>> Thanks so much for your helps,
>>>>
>>>> Van Thinh
>>>>
>>>>
>>>> From: Dmitri Leonov <dleonov at ocean.washington.edu>
>>>> Date: February 10, 2006 12:51:35 PM PST
>>>> To: mitgcm-support at mitgcm.org
>>>> Subject: Re: [MITgcm-support] How to reduce a reflection wave  
>>>> from  OBCs!
>>>> Reply-To: mitgcm-support at mitgcm.org
>>>>
>>>>
>>>> Hello Van Thinh,
>>>>
>>>> I've used sponge boundary conditions for a similar problem. My   
>>>> data.obcs file looks like this
>>>>
>>>> &OBCS_PARM01
>>>> OB_Iwest=1,
>>>> OB_Ieast=-1,
>>>> useOBCSsponge=.TRUE.,
>>>> &
>>>>
>>>> &OBCS_PARM03
>>>> spongeThickness=10,
>>>> # inverse relax. coef's (seconds)
>>>> Urelaxobcsinner = 0.0,
>>>> Urelaxobcsbound = 32.0,
>>>> Vrelaxobcsinner = 0.0,
>>>> Vrelaxobcsbound = 32.0,
>>>> &
>>>>
>>>> You may want to try it.
>>>>
>>>> Dmitri
>>>>
>>>>
>>>
>>>
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>>
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