Constitutive Models

Constitutive models describe relations between various physical quantities. In a physics simulation they are used to model the response or state of material (solid, fluid, or a mixture) as a function of input variables. There are many types of constitutive models available in GEOS. These models are grouped together based on their input/output interface.

• Solid Models
• Fluid Models
• Relative Permeability Models
• Capillary Pressure Models
• Porosity models
• Permeability models
• Porous Solids
• Temperature-dependent Solid Volumetric Heat Capacity Model
• Temperature-dependent Thermal Conductivity Model

In an input XML file, constitutive models are listed in the <Constitutive> block. Each parameterized model has its own XML tag, and each must be assigned a unique name via the name attribute. Names are used to assign models to regions of the physical domain via the materialList attribute of the <CellElementRegion> node (see XML Element: ElementRegions). In some cases, physics solvers must also be assigned specific constitutive models to use (see Physics Solvers).

A typical <Constitutive> and <ElementRegions> block will look like:

<Problem>

  <Constitutive>

    <!-- Define a compressible, single-phase fluid called "water"-->
    <CompressibleSinglePhaseFluid
      name="water"
      referencePressure="2.125e6"
      referenceDensity="1000"
      compressibility="1e-19"
      referenceViscosity="0.001"
      viscosibility="0.0"/>

  </Constitutive>

  <ElementRegions>

    <!--Add water to the material list for region 1-->
    <CellElementRegion
       name="region1"
       cellBlocks="{ * }"
       materialList="{ water }"/>

  </ElementRegions>

  ... remainder of problem definition here ...

</Problem>