# Viscosity-Temperature Coupling

This section describes the parameters for properly modeling viscosity-temperature coupling.

```
viscTempModels
{
viscTemp_model
{
phase_affected 1
viscTemp_model POLYNOMIAL
poly_coeffs1 0.0
poly_coeffs2 0.0
poly_coeffs3 0.0
poly_coeffs4 0.0
poly_coeffs5 0.0
}
viscTemp_model
{
phase_affected 1
viscTemp_model SUTHERLAND
sutherland_refVisc 0.1
sutherland_refTemp 273.15
sutherland_coefficient 12.01
}
viscTemp_model
{
phase_affected 1
viscTemp_model POWER_LAW
power_refVisc 1.716e-5
power_refTemp 273.15
power_exponent 0.666
}
}
```

`phase_affected`- Similar to the
`phase_motion`command, this option tells you which phase is affected by this viscosity-temperature dependence model. `viscTemp_model`- Model according to which the viscosity will be calculated as a function of temperature.

`poly_coeffs1`,`poly_coeffs2`,`poly_coeffs3`,`poly_coeffs4`, and`poly_coeffs5`- Polynomial coefficients for the polynomial viscosity-temperature model.
`sutherland_refVisc`- Sutherland reference viscosity.
`sutherland_refTemp`- Sutherland reference temperature
`sutherland_coefficient`- Sutherland coefficient
`power_refVisc`- Power law reference viscosity
`power_refTemp`- Power law reference temperature
`power_coefficient`- Power law exponent

`viscTempCoupling`capability, all of the FLUID phases must have their viscosities defined by one of the three

`viscTempCoupling`models. It is not possible to have one FLUID phase with constant viscosity and others with variable viscosity.