Equations of State#
The density of water can be specified in many ways, depending upon phase and problem of interest. Options are available from the simplest (constant value) to functions of just temperature, temperature and pressure, and temperature/pressure/concentration (e.g. salinity). We call these Equations of State (EOS).
Note that density includes both molar and mass-based values. Most density evaluators can provide either, or do provide both, the difference being simply a factor of the molecular mass of water.
Constant Value#
Like any quantity, a density can simply be a constant value, at which point it is not a secondary variable but an independent variable.
<ParameterList name="surface-molar_density_liquid" type="ParameterList">
<Parameter name="field evaluator type" type="string" value="independent variable constant" />
<Parameter name="value" type="double" value="55000" />
<Parameter name="units" type="string" value="mol m^-3" />
</ParameterList>
Standard Equation of State#
src/physics/ats/src/constitutive_relations/eos/eos_evaluator.hh
This evaluates an EOS as a function of temperature, pressure, and/or mole ratio/concentration.
evaluator-eos-spec
“EOS parameters”
[eos-typedinline-spec]
KEYS:
“molar density” Note that molar density is [mol H2O m^-3]. This is a _component_ quantity.
“mass density” Note that mass density is [kg m^-3]. This is a _phase_ quantity.
DEPENDENCIES:
“temperature”
“pressure”
“molar ratio”
Models#
Constant EOS#
src/physics/ats/src/constitutive_relations/eos/eos_constant.hh
A constant molar and mass density of water, independent of temperature or concentration, but related to each other by a molar mass of water.
Note, users should prefer to use “independent variable constant” to this.
“EOS type” = “constant”
eos-constant-spec
ONE OF
“molar mass [kg mol^-1]”
[double]0.0180153
OR
“molar mass [g mol^-1]”
[double]18.0153
END
ONE OF
“density [mol m^-3]”
[double]molar density of water
OR
“density [kg m^-3]”
[double]mass density of water
END
Linear EOS#
src/physics/ats/src/constitutive_relations/eos/eos_linear.hh
Ideal Gas#
src/physics/ats/src/constitutive_relations/eos/eos_ideal_gas.hh
Implements the ideal gas EOS, which computes n as a function of p and T. Default properties are that of air.
“EOS type” = “ideal gas”
eos-ideal-gas-spec
“ideal gas constant [J mol^-1 K^-1]”
[double]8.3144621
ONE OF
“molar mass of gas [kg mol^-1]”
[double]0.028956
OR
“molar mass of gas [g mol^-1]”
[double]28.956
END
EOS of Water#
src/physics/ats/src/constitutive_relations/eos/eos_water.hh
A molar and mass density of liquid water, empirically fit to data as a function of both pressure and temperature.
“EOS type” = “liquid water”
eos-liquid-water-spec
ONE OF
“molar mass [kg mol^-1]”
[double]0.0180153
OR
“molar mass [g mol^-1]”
[double]18.0153
END
EOS of Ice#
src/physics/ats/src/constitutive_relations/eos/eos_ice.hh
A molar and mass density of solid water, empirically fit to data as a function of both pressure and temperature.
“EOS type” = “ice”
eos-ice-spec
ONE OF
“molar mass [kg mol^-1]”
[double]0.0180153 \(M\) above
OR
“molar mass [g mol^-1]”
[double]18.0153
END
EOS of Vapor in Air#
src/physics/ats/src/constitutive_relations/eos/eos_vapor_in_gas.hh
A molar and mass density of gas including water vapor. This wraps another EOS for providing molar density, but removes mass density functions as they are not valid for this use case. Typically this wraps the ideal gas law EOS.
“EOS type” = “vapor in gas”
eos-vapor-in-gas-spec
“gas EOS parameters”
[eos-typedinline-spec]