Integral viscoelastic models

Integral viscoelastic models

Ver: 3

DESCRIPTION

Allows the user to select the viscoelastic integral constitutive model in use for the current sub-task.

The default selection is specified in the header.

OPTIONS

-1
Upper level menu

1' Switch to Generalized Newtonian Flow

Select this option to solve a generalized Newtonian flow problem with a shear-thinning behaviour which is identical to that of the integral model being defined.
Not available for shell models.

1" Switch to Viscoelastic Model

Contrary of option 1'.
By default, an integral viscoelastic flow problem is solved.
Not available for shell models.

2' Switch to Doi-Edwards model

This option should be selected for a Doi-Edwards model.
Not available for shell models.

2" Switch to KBKZ model

This option should be selected for a KBKZ model.
The KBKZ model is the default selection.
The KBKZ model is mandatory for shell models.

3 Modify the spectrum

Select this option to enter the spectrum of relaxation times by means of pairs of points <relaxation force-time> or <viscosity-time>
See "Modification of the spectrum" for more details.

4 Modify the damping function

This option is valid for the KBKZ model only.
The default is : Logde-Maxwell (no damping function).
See "Damping function" for more details.
Not available for shell models.

5 Ratio of the diff.of Norm. stresses (N2/N1)

This option is valid for the KBKZ model only and allows the user to set the ratio of the normal stresses differences.
A constant viscosity Newtonian counterpart can be added to the viscoelastic stresses.
Not available for shell models.

6 Modification of the additional viscosity

A constant viscosity Newtonian counterpart can be added to the viscoelastic stresses

7 Management of the evolutive viscosity

The evolutive viscosity is a parameter which affects the iterative technique.
This option allows the user to enter a sub-menu dedicated to the evolution of the evolutive viscosity.
See "Evolutive viscosity" for more details.
Not available for shell models.

8 Numerical integration

Selecting this option allows the user to specify some requirements about the tracking of the viscoelastic stresses.
See "Integration parameters" for more details.
Not available for shell models.

9 Temperature dependence

For non-isothermal flow problems of integral fluids, a temperature dependence can be defined for the relaxation spectrum.
In the particular case of an inelastic fluid (see option 1), this temperature dependence applies on the shear viscosity.
The following models are available :

no temperature dependence

Arrhenius approximate law

Arrhenius law

WLF dependence

Not available for shell models.

NOTES In view of the non-linearities intrinsic to viscoelastic models, a non-linear strategy must be used to reach high Weissenberg numbers.

The flow rate or the relaxation time can be incremented by means of an evolutionary task. However, the method of going from a
Newtonian to an integral viscoelastic flow problem by means of an evolutive viscosity works better.

SEE ALSO

integral viscoelastic flow problems (UM)
viscoelastic fluid of the integral type (TB)
continuum equations (TB)
evolution (TB)
s-dependence (RM)
create a new task (RM)
system of units (RM)

-1	Upper level menu
1'	Switch to Generalized Newtonian Flow
	Select this option to solve a generalized Newtonian flow problem with a shear-thinning behaviour which is identical to that of the integral model being defined. Not available for shell models.
1"	Switch to Viscoelastic Model
	Contrary of option 1'. By default, an integral viscoelastic flow problem is solved. Not available for shell models.
2'	Switch to Doi-Edwards model
	This option should be selected for a Doi-Edwards model. Not available for shell models.
2"	Switch to KBKZ model
	This option should be selected for a KBKZ model. The KBKZ model is the default selection. The KBKZ model is mandatory for shell models.
3	Modify the spectrum
	Select this option to enter the spectrum of relaxation times by means of pairs of points <relaxation force-time> or <viscosity-time> See "Modification of the spectrum" for more details.
4	Modify the damping function
	This option is valid for the KBKZ model only. The default is : Logde-Maxwell (no damping function). See "Damping function" for more details. Not available for shell models.
5	Ratio of the diff.of Norm. stresses (N2/N1)
	This option is valid for the KBKZ model only and allows the user to set the ratio of the normal stresses differences. A constant viscosity Newtonian counterpart can be added to the viscoelastic stresses. Not available for shell models.
6	Modification of the additional viscosity
	A constant viscosity Newtonian counterpart can be added to the viscoelastic stresses
7	Management of the evolutive viscosity
	The evolutive viscosity is a parameter which affects the iterative technique. This option allows the user to enter a sub-menu dedicated to the evolution of the evolutive viscosity. See "Evolutive viscosity" for more details. Not available for shell models.
8	Numerical integration
	Selecting this option allows the user to specify some requirements about the tracking of the viscoelastic stresses. See "Integration parameters" for more details. Not available for shell models.
9	Temperature dependence
	For non-isothermal flow problems of integral fluids, a temperature dependence can be defined for the relaxation spectrum. In the particular case of an inelastic fluid (see option 1), this temperature dependence applies on the shear viscosity. The following models are available : no temperature dependence Arrhenius approximate law Arrhenius law WLF dependence Not available for shell models.