# [CIG-MC] I need a material model with depth dependent density (only).

Elbridge Gerry Puckett egp at math.ucdavis.edu
Sat Jul 23 17:15:25 PDT 2016

Dear Eric,

I'm pretty certain your suggestion will  not work for our problem: note

\Delta T = T - T_0

where T_0 is a reference temperature. The destiny depends on T
I need a material model of the form

\rho_0 + \Delta \rho + \rho_0 \alpha \Delta T    = if z < 0.5 D

\rho(T) =

\rho_0 - \Delta \rho + \rho_0 \alpha \Delta T     = if z > 0.5 D

where D is the height of the domain.

but the equation is different when z < 0.5 than when z > 0.5.  Again, note that The density in this model does NOT advect with the flow; i.e., we do not solve

D \rho / D t = 0

where D  / D is the material derivative.

> On Jul 22, 2016, at 7:22 PM, 譚諤 (Eh Tan) <tan2 at earth.sinica.edu.tw> wrote:
>
>
> You will need to modify the code. You can use these parameters to provide your density profile:
> reference_state=0
> refstate_file=refstate.dat
>
> The file refstate.dat will have nodez lines, and each line has 7 columns. The meaning of the columns are:
> rho, g, alpha, cp, not_used, not_used, not_used
>
> You can modify the code to use one of the not_used column for your depth-dependent \Delta \rho.
>
> Regards,
> --------
> 譚諤 (Eh Tan)
> Assistant Research Fellow
> Institute of Earth Sciences
> http://www.earth.sinica.edu.tw/~tan2/tan2_e.html
> Tel: +886-2-27839910 ext.503
>
>
>> On Fri, Jul 22, 2016 at 9:18 AM, Elbridge Gerry Puckett <egpuckett at ucdavis.edu> wrote:
>> Hi,
>>
>> I need a material model of the form
>> Note: The density in this model does NOT advect with the flow; i.e., we do not solve
>>
>> D \rho / D t = 0
>>
>> where D  / D is the material derivative.
>>
>> Furthermore, we DON'T want to use a compositional field or tracers.
>> Do I need to write my own material model or is there one that will work.
>>
>> If I need to write my own, is the simple material model a better place to start than the depth dependent viscosity material model?
>>
>> Thanks!
>>
>> - G
>>
>>
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>
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