# How to define the property of media according to two variables (e.g. pressure and temperature)?

Dear all,

I’m working on a THM process to investigate the fault stability influenced by EGS stimulation. According to my experience, the equation of state (EOS) of water may paly a critical role on this coupled poros media process. Furthermore, I also found some advanced configuration in the OGS6, OGS: [tag] property. However, when I try to give a exact value of the thermal conductivity of water, I find two variables, those are the temperature and pressure of water, are needed to determine the thermal conductivity of water. And the temperature and pressure can be calculated in the OGS6, but I didn’t find an available case in this page, OGS: [tag] property, to get a corresponding value of thermal conductivity of water based on those two known (or calculated) variables. I have used curve, OGS: [case] Curve, to define a property of media according to one variable. But, how to realize to define a property of media according to two variables (e.g. pressure and temperature)?

Btw, I read a paper that uses freesteam application, http://freesteam.sourceforge.net/, to get the properties of water, since these properties are the functions of its thermodynamic state. This paper is using OGS5, so I want to ask whether OGS6 can also realize the similar function?
Could anyone give me some clues or advices?

Thanks!

Hi @Rui_Feng ,
this example contains the density composed of two independent variables:
Tests/Data/ThermoHydroMechanics/Linear/Storage/cube_isochoric_heat-up.prj · master · ogs / ogs · GitLab (mimicking fluid compressibility and thermal expansivity)
This should work in principle also for the thermal conductivity.
For more complex behavior a new property might be required.

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