Viscosity Models
This section describes the parameters for properly enabling various viscosity models.
Attention: As of nanoFluidX 2022.2, several
changes have occurred for viscosity modeling.
 The aerationviscosity coupling has been deprecated as practical use of these models was not viable (need for model calibration, lack of manufacturer specifications).
 The existing temperatureviscosity coupling model commands have changed format and are now incorporated into the new viscosity models section.
 Cross model nonNewtonian fluids are now available in nanoFluidX, also conveniently associated with the viscosity model section.
 If these simulation parameters are kept false, then the standard dynamic viscosity definition in the Phases Parameters takes precedence.
 If either varvisc_temperature or varvisc_non_Newtonian are enabled (set to true), and a fluid phase is missed in the Viscosity Models section  the missed fluid will be assumed Newtonian and the standard dynamic viscosity definition from the Phase Parameters is assumed. It is best practice that if either varvisc_temperature or varvisc_non_Newtonian are enabled, you proceed using the Viscosity Models section for definition of all phase viscosity models.
For more information about viscosity models, refer to Viscosity Models in the Theory Manual.
Important: These changes are not backward
compatible, so configuration files utilizing temperature or aerationviscosity
coupling and created for versions prior to 2022.2 will not be able to run in
2022.2 or later versions of nanoFluidX.
Commands
viscosityModels
{
viscosityModel
{
viscosityModel_type FLUID_NEWTONIAN
viscosityModel_phase 1
viscosityModel_visc 1e3
}
viscosityModel
{
viscosityModel_type FLUID_S_CROSS
viscosityModel_phase 3
viscosityModel_k 1.0
viscosityModel_n 0
viscosityModel_visc_0 1e3
viscosityModel_visc_inf 1e3
}
viscosityModel
{
viscosityModel_type FLUID_T_POLYNOMIAL
viscosityModel_phase 4
viscosityModel_c "1e3 0.0 0.0 0.0 0.0"
}
viscosityModel
{
viscosityModel_type FLUID_T_SUTHERLAND
viscosityModel_phase 5
viscosityModel_visc_ref 1.716e5
viscosityModel_temp_ref 273.15
viscosityModel_temp_sut 110.4
}
viscosityModel
{
viscosityModel_type FLUID_T_POWER_LAW
viscosityModel_phase 6
viscosityModel_visc_ref 1e3
viscosityModel_temp_ref 273.15
viscosityModel_n 0
}
}
Definitions
Command  Contents  SI Unit Example 

viscosityModel_type  Viscosity model choice which will be assigned to the
respective fluid phase (viscosityModel_phase) Options
Attention: Only one model can be selected
per phase. 

viscosityModel_phase  Phase ID of the fluid phase which is affected by the selected model choice.  
viscosityModel_visc  Dynamic viscosity when using the Newtonian fluid
model. Default = 0.001 
[Pa.s] 
viscosityModel_k  Dimensionless coefficient k for the Cross model (see Viscosity Models for more
information). Default = 0.001 

viscosityModel_n  Serves as a dimensionless power exponent in the Cross model
for nonNewtonian viscosity and Power Law temperature dependence
model (see Viscosity Models for
more information). Default = 0.0 

viscosityModel_visc_0  Zero shear rate viscosity for the Cross model. Default = 0.001 
[Pa.s] 
viscosityModel_visc_inf  Infinite shear rate viscosity for the Cross model. Default = 0.001 
[Pa.s] 
viscosityModel_c  Coefficients for the temperatureviscosity polynomial model.
This is a vector variable, comprising of 5 values defined in
order of the polynomial. Default = "0.001 0.0 0.0 0.0 0.0" 
[Pa.s, Pa.s/T, Pa.s/T^{2}, Pa.s/T^{3}, Pa.s/T^{4}] 
viscosityModel_temp_ref  Base temperature of the Sutherland temperatureviscosity
dependence model. Default = 273.15 
[K] 
viscosityModel_visc_ref  Base viscosity of Sutherland temperatureviscosity dependence
model. Default = 0.00001716 
[Pa.s] 
viscosityModel_sut  Sutherland temperature (also known as Sutherland's
coefficient). Default = 110.4 
[K] 