[CIG-LONG] CIG-LONG Digest, Vol 42, Issue 9

Mon May 10 10:35:58 PDT 2010

Hi Gilly,

Thank you for your response.  I tried adding in the hydrostatic  
pressure but now I am getting very high magnitude pressure values on  
each of the 4 corners of my simulation box.

With the addition of the hydrostatic stress I now have two stress  
boundary conditions, as shown below.  The bottom stress boundary  
condition is equal to the weight of the material in the box.  Without  
the hydrostatic term I do get a linear gradient, but it doesn't go to  
zero at the top of the simulation box like I would have thought.  I  
would think that this bottom stress boundary condition may need to be  
altered with the addition of the hydrostatic term, but i'm not sure  
how.  If I set the bottom boundary condition to zero then I get an  
error and the code won't run.  Ideally I would like to set pressure  
boundary conditions along the top, bottom and sides, so I'm hoping  
there is a way to do this without specifying velocity boundary  
conditions.

Do you have any idea what might be going wrong?

Thanks,
Karen

    <struct name="buoyancyForceTerm">
      <param name="Type">BuoyancyForceTerm</param>
      <param name="ForceVector">mom_force</param>
      <param name="Swarm">picIntegrationPoints</param>
      <param name="gravity">gravity</param>
      <param name="HydrostaticTerm">hydrostaticTerm</param>
    </struct>

    <struct name="hydrostaticTerm">
      <param name="Type">HydrostaticTerm</param>
      <param name="upperDensity">3000</param>
      <param name="height">maxY</param>
      <param name="gravity">gravity</param>
    </struct>

    <struct name="stressBCBottom">
      <param name="Type">StressBC</param>
      <param name="ForceVector">mom_force</param>
      <param name="Swarm">picIntegrationPoints</param>
      <param name="wall">bottom</param>
      <param name="y_type">double</param>
      <param name="y_value">1.29492e10</param> <!--rho*g*ymax-->
    </struct>

    <struct name="stressBCTop">
      <param name="Type">StressBC</param>
      <param name="ForceVector">mom_force</param>
      <param name="Swarm">picIntegrationPoints</param>
      <param name="wall">top</param>
      <param name="y_type">HydrostaticTerm</param>
      <param name="y_value">hydrostaticTerm</param>
    </struct>
On May 10, 2010, at 10:33 AM, <Guillaume.Duclaux at csiro.au> <Guillaume.Duclaux at csiro.au 
 > wrote:

> Karen,
>
> What you describe sounds pretty similar to the standard  
> HydrostaticTerm StressBC implementation in Gale.
> You can adapt the HydrostaticTerm example defined in tibet.xml  
> component.
> For a linear hydrostatic stress profile (one material with a density  
> of 2800 kg/m3, no thermal exp.), you first define the  
> HydrostaticTerm function, then apply the StressBC (and make sure the  
> hydrostaticTerm is added to the buoyancyForceTerm).. it should do  
> the job!
>
>    <struct name="hydrostaticTerm">
>      <param name="Type">HydrostaticTerm</param>
>      <param name="upperDensity">2800</param>
>      <param name="upperAlpha">0</param>
>      <param name="lowerDensity">2800</param>
>      <param name="lowerAlpha">0</param>
>      <param name="height">maxY</param>
>      <param name="materialBoundary">0</param>
>      <param name="T_0">TemperatureProfileTop</param>
>      <param  
> name="linearCoefficient">TemperatureProfileLinearCoefficient</param>
>      <param  
> name 
> = 
> "exponentialCoefficient1">TemperatureProfileExponentialCoefficient1</ 
> param>
>      <param  
> name 
> = 
> "exponentialCoefficient2">TemperatureProfileExponentialCoefficient2</ 
> param>
>      <param name="gravity">gravity</param>
>    </struct>
>
>    <struct name="stressBC">
>      <param name="Type">StressBC</param>
>      <param name="ForceVector">mom_force</param>
>      <param name="Swarm">picIntegrationPoints</param>
>      <param name="wall">top</param>
>      <param name="y_type">HydrostaticTerm</param>
>      <param name="y_value">hydrostaticTerm</param>
>    </struct>
>    <struct name="buoyancyForceTerm">
>      <param name="Type">BuoyancyForceTerm</param>
>      <param name="ForceVector">mom_force</param>
>      <param name="TemperatureField">TemperatureField</param>
>      <param name="Swarm">picIntegrationPoints</param>
>      <param name="gravity">gravity</param>
>      <param name="HydrostaticTerm">hydrostaticTerm</param>
>    </struct>
>
>
> Cheers
>
> Gilly
> ________________________________________________
>
> Dr Guillaume Duclaux
> CSIRO Earth Science and Resource Engineering
> Visiting address: ARRC, 26 Dick Perry Av., Kensington WA 6151
> Postal address: PO Box 1130, Bentley WA 6102, Australia
> Ph: + 61 8 6436 8728    Fax: + 61 8 6436 8555    Web: www.csiro.au
> ________________________________________
> From: cig-long-bounces at geodynamics.org [cig-long-bounces at geodynamics.org 
> ] On Behalf Of Karen Paczkowski [karen.paczkowski at yale.edu]
> Sent: Monday, 10 May 2010 22:10
> To: cig-long at geodynamics.org
> Subject: Re: [CIG-LONG] CIG-LONG Digest, Vol 42, Issue 9
>
> Hi Walter,
>
> I see from the manual that I can make a stress boundary condition
> shaped like a Gaussian.  How can I make one that is just a linear
> gradient?  I would like to set the pressure on the bottom of the
> simulation box equal to hydrostatic pressure (rho g ymax) and then
> have the pressure linearly decrease to zero at the top of the
> simulation box.
>
> Thanks,
> Karen
>
> On May 7, 2010, at 3:00 PM, cig-long-request at geodynamics.org wrote:
>
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>> Today's Topics:
>>
>>  1. Re: Low viscosity material around dike
>>     (Guillaume.Duclaux at csiro.au)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Fri, 7 May 2010 05:07:35 +0800
>> From: <Guillaume.Duclaux at csiro.au>
>> Subject: Re: [CIG-LONG] Low viscosity material around dike
>> To: <walter at geodynamics.org>, <cig-long at geodynamics.org>
>> Message-ID:
>>      <F208C10EED02964CB3F9014E661F55024F11FA638F at EXWA-
>> MBX01.nexus.csiro.au>
>> Content-Type: text/plain; charset="us-ascii"
>>
>> Folks,
>>
>> I'm currently out of office and I didn't bring my scaling scripts
>> with me... The NewNewtonian rheology in Gale implies some scaling
>> (in order to obtain an effective viscosity of the order of one), you
>> can't directly use values from the literature.
>>
>> I'll detail the scaling for each parameter in the NonNewtoninan
>> constitutive law as soon as I can acces my machine.
>>
>> Cheers
>>
>> Gilly
>> ________________________________________________
>>
>> Dr Guillaume Duclaux
>> CSIRO Earth Science and Resource Engineering
>> Visiting address: ARRC, 26 Dick Perry Av., Kensington WA 6151
>> Postal address: PO Box 1130, Bentley WA 6102, Australia
>> Ph: + 61 8 6436 8728    Fax: + 61 8 6436 8555    Web: www.csiro.au
>> ________________________________________
>> From: cig-long-bounces at geodynamics.org [cig-long-bounces at geodynamics.org
>> ] On Behalf Of Walter Landry [walter at geodynamics.org]
>> Sent: Thursday, 6 May 2010 23:42
>> To: cig-long at geodynamics.org
>> Subject: Re: [CIG-LONG] Low viscosity material around dike
>>
>> Taichi SATO <taichix at aori.u-tokyo.ac.jp> wrote:
>>> Dear Walter,
>>>
>>> Thank you very much!
>>> I think the value of power law constant "A" depends on material
>>> such as wet
>>> basalt and dry olivine.
>>> Which material do you assume by using the value, A = 1.0E-16?
>>
>> I got my numbers from someone else (Guillame?), and I do not know  
>> what
>> he was assuming.
>>
>>> I can not still resolve the problem about the dike region.
>>> Although I am trying to resolve this problem, please give me some
>>> ideas.
>>
>> Did you try submerging the dike even further?  Eventually, you should
>> no longer have a dike hill.
>>
>> Cheers,
>> Walter Landry
>> walter at geodynamics.org
>> _______________________________________________
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>> End of CIG-LONG Digest, Vol 42, Issue 9
>> ***************************************
>
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