[MITgcm-support] The criteria of cg3dMaxIters

[Saeid Esmaeilpour]

Yes they have.

Saeid

On Tue, Aug 15, 2017 at 1:14 PM, Jody Klymak <jklymak at uvic.ca> wrote:

>
>
> On 15 Aug 2017, at 9:58, Saeid Esmaeilpour wrote:
>
> Thanks again Jody,
>> It was really helpful, for the last question about this issue, Do I need
>> nonHydrostatic=.True. for the simulation of Eddies? Isn't that a
>> fine-scale
>> phenomena? will MIT show up  Eddies at 2-degree resolution?
>>
>
> Do your eddies have large dw/dt?
>
> Are they about 12-degrees across?
>
> Cheers,  Jody
>
>
>
>> Thanks,
>>    Saeid
>>
>> On Tue, Aug 15, 2017 at 12:42 PM, Jody Klymak <jklymak at uvic.ca> wrote:
>>
>> On 15 Aug 2017, at 9:29, Saeid Esmaeilpour wrote:
>>>
>>> Jody,
>>> my model is about The simulation of currents Circulation from surface to
>>> depth in indian Ocean, and I selected nonHydrostatic=.TRUE., cause I
>>> think the model resolve the Nonlinear terms with nonHydrastatic=True (am
>>> I
>>> wrong ?). If I select nonHydrastatic=True, in this case how much should I
>>> set for cg3MaxIters? and If select nonHydrastatic=False, how much for
>>> that?
>>> basically for the simulation of currents Circulation and at 2-degree I
>>> have
>>> to take non Hydraustatic=false?
>>>
>>> nonHydrostatic=.True. solves the non-hydrostatic equation for dw/dt,
>>> which essentially means the pressure needs to be determined globally
>>> from a
>>> Poisson equation, and hence the 3-D solver. .False. means that pressure
>>> is solved using the hydrostatic approximation (if you don’t know what
>>> this
>>> is, Google plus a basic GFD course would help).
>>>
>>> This really has nothing to do with non-linearity until you start
>>> resolving
>>> scales where the hydrostatic approximation breaks down (basically dw/dt
>>> is
>>> no longer << rho’g / rho_0).
>>>
>>> You really only need non-hydrostatic approximation for fine-scale runs
>>> looking at internal waves, dense overflows, convection, or other
>>> turbulent
>>> phenomena. None of which will show up at 2-degree resolution.
>>>
>>> Cheers, Jody
>>>
>>> Thanks again,
>>> Saeid
>>>
>>> On Tue, Aug 15, 2017 at 11:59 AM, Jody Klymak <jklymak at uvic.ca> wrote:
>>>
>>> Hi Saied,
>>>
>>> cg3dMaxIters is only used if nonHydrostatic=.True.. You aren’t resolving
>>> any non-hydrostatic physics at 2-degree resolution, so I would suggest
>>> setting nonHydrostatic=.False. Your model runs will be *much* faster.
>>>
>>>
>>> Cheers, Jody
>>>
>>> On 15 Aug 2017, at 8:43, Saeid Esmaeilpour wrote:
>>>
>>> Hi Dear users,
>>> could someone please explain to me what are the following PARM02?
>>> when I increase cg3dMaxIters from 50 to 400 (e.g,. cg3dMaxIters=400) the
>>> run speed becomes very slowly. how can I select this value? what's the
>>> criteria for selecting this number? My domain is 510*210 with 20layer and
>>> also my resolution is 2 degree (3704m).
>>>
>>> # Elliptic solver parameters
>>> &PARM02
>>> cg2dMaxIters=1000,
>>> cg2dTargetResidual=1.E-13,
>>> cg3dMaxIters=400,
>>> cg3dTargetResidual=1.E-13,
>>>
>>> Thanks for any help,
>>> Saeid
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>
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