[MITgcm-support] Smagorinsky viscosity

[Jody Klymak]

> Do I understand it correctly though that Smag3D uses the same viscosity coefficient for the horizontal and vertical? I’m using a 1:5 grid aspect ratio, so I don’t think I would want that. 

Yes, Smagorinsky uses just one viscosity for all three dimensions.  

I'm not sure why you would want 3-D Smagoronsky if your grid is 1:5.  Non-hydrostatic is a bit questionable as well.  What are you trying to simulate?

Cheers,   Jody



> Thanks,
> Malte
> 
>> On Mar 12, 2015, at 3:37 PM, Jody Klymak <jklymak at uvic.ca> wrote:
>> 
>> Hi Malte,
>> 
>> I just looked into this with Ruth Musgrave's help as well.  3-D Smagorinsky works pretty well. Your grid can be anisotropic, but probably not too anisotropic.  If you are using non-hydrostatic you probably don't want a grid that is too anisotropic anyways.   As written, it does not do any enhanced diffusivity, though I have a straight forward mod to enhance the diffusivities as well.  I guess I dont' know about any issues with the vertical advection scheme.  I'd have to take a look at it.  
>> 
>> I believe it just uses Dearborn's scheme.  So the Smagorinsky constant is just a constant.  I found to get energy to balance you had to tune this constant, so it would be great if someone moved towards a Germano type scheme.
>> 
>> I dont' have access to my files right now, but will in a few hours, but its pretty straightforward to try.  A little less straightforward if you want your own diagnostics into the dissipation terms and matching diffusivity.
>> 
>> I don't know anything about 2-D Smagorinsky.  
>> 
>> Cheers,   Jody
>> 
>>> On Mar 12, 2015, at  4:03 AM, Malte Jansen <mfj at uchicago.edu> wrote:
>>> 
>>> Hi all,
>>> 
>>> Can anybody give me (or point me to) a brief update on the Smagorinsky viscosity implementation? The documentation seems to say that the vertical component of the Smagorinsky viscosity has not yet been implemented. Is that still true? 
>>> 
>>> I also found an old post stating that Smag does not yet work at all for the non-hydrostatic version. Is that still true?
>>> 
>>> There now also is a Smag3D. Is there any documentation for that? Do I see it correctly that Smag3D is fully isotropic (and thus probably not recommended if the model grid is anisotropic)?
>>> 
>>> I am running a non-hydrostatic model with non-isotropic grid. So my question is basically if there is an existing implementation of the Smagorinsky viscosity that should be adequate?
>>> 
>>> Thanks,
>>> Malte
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>> 
>> 
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--
Jody Klymak    
http://web.uvic.ca/~jklymak/