[MITgcm-support] Using a sponge layer to relax temperature

[Stroman, Ashley]

Hi Dustin.

My main reason for using Orlanski is so that when my vortices hit the boundaries, I want them to exit my domain and not return back inside my domain.  So in my mind I had two ideas:

1.) Use Orlanski for momentum and use the sponge layer for temperature at the boundaries

or

2.) Use the sponge layer for both momentum and temperature at the boundaries

I was just worried about option 1) because I know if you use OBCSprescribe then you can’t also use Orlanski, at least from what I’ve read. And I couldn’t find anything on whether or not this also pertains to using OBCSsponge and Orlanski.

Best,
Ashley
On Mar 2, 2015, at 1:24 PM, Dustin Carroll <dcarroll at uoregon.edu<mailto:dcarroll at uoregon.edu>> wrote:

Hi Ashley,

I don’t see anything in the code that would prevent you from using Orlanski + sponge layer. Perhaps someone on the development side of things can verify this.
What is your reason for using Orlanski — are you having trouble with waves reflecting back into your domain of interest?

Looks like the OBCSsponge_theta flag just gives you more control over your sponge layer. Specifically if you only want to relax temperature fields (and not u/v and salt). Check out OBCS_PARAMS.h.

Cheers,
Dustin




On Mar 2, 2015, at 9:56 AM, Stroman, Ashley <acs08g at my.fsu.edu<mailto:acs08g at my.fsu.edu>> wrote:

Hi Dustin.

I have two specific questions regarding my problem:

1.) Is it possible to use Orlanski for momentum on the boundaries, while also using a sponge layer to restore temperature to the initial conditions on the boundaries? I’m not sure if both are allowed, and I’ve had no luck finding this answer online.

2.) What is the difference between useOBCSsponge and OBCSsponge_Theta in the data.obcs file? My thought is that the latter is specifically used for theta while the former is not, but I am not 100% positive. There’s not much information on the latter parameter except that it turns on the theta sponge along the boundaries, so I’m not sure if the parameter is used, 1) what it specifically means, and 2) what is additionally required.

Thanks.
Ashley
On Feb 27, 2015, at 8:06 PM, Dustin Carroll <spanishcastlemagik at gmail.com<mailto:spanishcastlemagik at gmail.com>> wrote:

Hi Ashley,

Can you provide a bit more information on the problem you are having? I find that the more specific you are, the easier it is for people to help on this support group.

Section 6.3.1 in the docs (see below) describes how to set up your data.obcs file, also look at verification/exp4 for an example w/ open boundaries.
http://mitgcm.org/public/r2_manual/latest/online_documents/node236.html

If you want to restore your boundaries to the prescribed ICs then you’ll need to generate binary files for each boundary that is specified in data.obcs,

Cheers,
Dustin


On Feb 27, 2015, at 11:56 AM, Stroman, Ashley <acs08g at my.fsu.edu<mailto:acs08g at my.fsu.edu>> wrote:

Hello.

I am wanting to use the OBCS package to implement a sponge layer on the boundaries to relax temperature to the initial conditions. I am having trouble finding what is needed in terms of the data.obcs file as well as any any additional binary files for temperature that are required. Can someone shed some light on this? Thanks.

Best,
Ashley Stroman
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