[MITgcm-support] Internal waves. Noise near bottom.

[fancer fancer]

Jody,

I worry about noise low frequency, what come from bottom steps. For
comparison I attached the screenshots of pictures from other model. These
pictures look more clearly, perhaps for reason what this model uses
sigma-coordinate. And I trying to create the MITgcm project with similar
output. Could you tell me Is this possible?

We are investigating an internal waves in closed basin, generated as a
result of deviation of pycnocline. These deviations may be caused for
various reason, for example, wind-surge phenomena and etc. I trying to make
a serial of experiments for comparison our model and MITgcm.

Thanks for response and interest.

Sincerely,
Serge Semin

On Sun, May 1, 2011 at 9:19 PM, Klymak Jody <jklymak at uvic.ca> wrote:

> The new runs look very different from the old run; all the very strong
> vertical excursions have been suppressed.   What "noise" are you worried
> about in the new runs?
>
> I can't quite tell what you are trying to do in your model, but note that
> shocks or solitons will not be properly represented unless you turn
> non-hydrostatic to be "on".  In hydrostatic mode, most shocks will try to
> dissipate energy by shedding grid-scale oscillations in their wake.  Perhaps
> some of the "steppiness" you are seeing is related to this phenomena.
>
> Finally, I would look at the cell-shaving code again, or perhaps someone
> who understands it better can suggest proper settings for it.  I don't think
> you are going to get rid of some internal waves being generated at the
> steps.  However, they should really have little energy and affect your
> solution very little.
>
> Cheers,   Jody
>
>
>
> On 2011-04-30, at 11:37 PM, fancer fancer wrote:
>
> Jody,
>
> Thanks for response.
> Now I've put diffusion, but still with no positive results (pictures with
> U,W and T in attach). I've set:
> diffKhT=1.E-2,
> diffKzT=1.E-3,
> diffK4T=0.E-3,
> diffShT=0.E-2,
> diffSzT=0.E-3,
> diffS4T=0.E-3,
> momViscosity=.TRUE.,
> viscAh=1.E-2,
> viscAz=1.E-3,
> But noise above bottom steps still present.
> Is it right value?
> Is there something else, what can help to restrain noises?
>
> Sincerely,
> Serge Semin
>
> On Fri, Apr 29, 2011 at 10:12 PM, Jody Klymak <jklymak at uvic.ca> wrote:
>
>> Serge,
>>
>> According to your "data" file you have no explicit viscosity or diffusion.
>> So any internal waves generated at the steps rattle around with only
>> numerical diffusivity to dissipate them.  I'd put some diffusivity and
>> viscosity in, even if it is molecular.
>>
>> Cheers,  Jody
>>
>>
>> On Apr 28, 2011, at  12:23 PM, fancer fancer wrote:
>>
>>  Hi Dear Modelers,
>>>
>>> I am trying to model ideal case of internal waves propagation in closed
>>> basin without free surface (rigid lid) in 2D area with two layer
>>> stratification (linear tilting) and parabolic bottom.
>>> Now I faced with problem of partial discretization. I can not get a
>>> simulation without noises near the largest steps of the bottom.
>>> I've tried to set various dx, dz and dt steps, but without positive
>>> result. I've tried to use  various tempAdvScheme (33, 77), unfortunately
>>> with same result. And finally I've tried to set various hFacMin, now it is
>>> in 0.00005 value (best results), but it didn't helped me too.
>>> We have an results of modelling through other system with
>>> sigma-coordinate discretization, where we set 1000x50 points on 10000x10 m
>>> grid. There's no noise.
>>> I put the pictures with T, U and W of modeling in result directory of
>>> attached project.
>>> Could you tell me how should I modify my project (in attach) for clearing
>>> the model? or how should I calculate dx and dz steps for model
>>> stabilization? (CFL in norm)
>>>
>>> And one more question. My area is 2D (z and x coordinates), but models
>>> stability depends of dy step. Is this normal or something wrong with my
>>> project? If second is true, could you tell me that can be wrong?
>>>
>>> Thanks for help in advance.
>>>
>>> Sincerely,
>>> Serge Semin
>>>
>>> <01_tilting_stratification_parabola.tar.gz>_______________________________________________
>>> MITgcm-support mailing list
>>> MITgcm-support at mitgcm.org
>>> http://mitgcm.org/mailman/listinfo/mitgcm-support
>>>
>>
>> --
>> Jody Klymak
>> http://web.uvic.ca/~jklymak/
>>
>>
>>
>>
>>
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>>
>
> <tilting_stratification_parabola.zip>
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