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

[Jennifer MacKinnon]

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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