Thermo Hydro Mechanics Process

This page describes Thermo-Hydro-Mechanics Process (THM).

Introduction

Theoretical background

Implementation

Supported phases

• Aqueous liquid
• Frozen liquid
• Solid

Input variables and parameters

List of medium properties required by THM process.

Medium properties

• bulk modulus
• density
• specific heat capacity

Those properties are defined on medium level. See medium properties for more details on defining them.

Thermo-osmosis can be parametrised in two, mutually exclusive, ways:

• thermal_osmosis_coefficient sets the thermo-osmotic coefficient $k_T$ ($[k_T] = m^2/(K \cdot s)$) directly. Use this when a tabulated $k_T$ is available.
• thermal_osmosis_permeability sets the scalar thermo-osmotic permeability $\epsilon_T$ ($[\epsilon_T] = Pa/K$), from which $k_T = \epsilon_T k / \mu$ is formed using the medium’s intrinsic permeability $k$ and the AqueousLiquid phase’s dynamic viscosity $\mu$. Use this when $\epsilon_T$ is the measured quantity and $k_T$ should track a spatially varying $k$ and a temperature-dependent $\mu$.

Note that thermal_osmosis_permeability is not a permeability and does not have a permeability’s dimension; the name was kept for continuity with the existing property naming.

Older project files defining thermal_osmosis_coefficient on the solid phase are moved to the medium level by the scripts/dev/move_thermal_osmosis.py helper script, which with --convert also rewrites the property as thermal_osmosis_permeability. A thermal_osmosis_coefficient already given on the medium level is a valid parametrisation and is left unchanged by the script.

Input parameters in the project file

THM process has to be declared in project file in the processes block. For example in following way:

<processes>
    <process>
        <type>THERMO_HYDRO_MECHANICS</type>
    </process>
</processes>

Process variables

Following process variables are available in THM process:

• temperature
• pressure
• displacement

For more details, see Process variables .

Example of full section defining THM process

Features

Specific body force

Thermal porosity mixing

THM can automatically obtain thermal conductivity for the medium based on thermal conductivities of phases and porosity.

See Thermal conductivity: effective porosity mixing for more information.

Examples

Available benchmarks

To gain more insight into THM process, you can investigate THM benchmarks .

References