The modified 2-domain Tait pvT model is used to determine the density of the material as a function of the temperature and pressure. This variation impacts on many aspects of the flow simulation.
The 2-domain Tait pvT model is given by the following equations:
where:
-
is the specific volume at temperature and pressure -
is the specific volume at zero gauge pressure -
is the temperature, in K -
is the pressure, in Pa -
is a constant, 0.0894 -
accounts for the pressure sensitivity of the material and is defined below.
The upper temperature region 
can be described by the equations:
where:
-
,
,
, 
and 
(which represents the volumetric transition temperature, 
, at zero gauge pressure) are data-fitted coefficients.
The lower temperature region 
can be described by the equations:
where:
-
, 
, 
, 
, , 
, 
, and 
are data-fitted coefficients
Note: The 
value for crystalline resins only applies to temperatures below the transition temperature.
value for crystalline resins only applies to temperatures below the transition temperature. The dependence of on pressure can be described by the equation:
where:
- and
are data-fitted coefficients