Index

Interface

Ver: 1
 

DESCRIPTION

The interface boundary condition is available along the intersections (lines or faces) of adjacent domains of two distinct sub-tasks.

This boundary condition ensures the continuity of the fields along the intersection,  along with the continuity of the force or flux (dual quantity).

If flow problems are defined on both domains, an interface boundary condition for the momentum equation ensures continuity of the velocity field and of the force vector between domains. For mobile interface, surface tension may be taken into account. Additional information is then required, for the kinematic condition and for the remeshing technique.

Interface boundary condition for the energy equation ensures continuity of the temperature field and of the heat flux. However, it is possible to specify a jump for the heat flux. This occurs for exemple in problems involving thermal radiation (see also 'flux_density_imposed').

The general form for the jump of the heat flux is

 
q = qc + alpha * [ T - Talpha ]
+ sigma * [ (T + T0) ** 4 - (Tsigma + T0) ** 4 ] ,
where qc is a temperature independent heat flux, alpha is a heat convection coefficient (with a reference temperature Talpha), and sigma is a radiation coefficient (with a reference temperature Tsigma). T0 is a shift factor to allow for the use of temperatures in Celsius.

By default : q = 0.


OPTIONS

For the momentum equation of flow problems, we have :
 
-1 Accept the current setup
1 Define a fixed interface
When the kinematic condition does not have to be considered
2 Define a moving interface
This option should be selected when the location of the current intersection is a priori unknown. A moving interface may include a surface tension.

For the energy equation, we have :
 
-1 Upper level menu
1 Modification of qc
The temperature independent contribution to the heat flux can depend upon coordinates
2 Modification of alpha
The heat convection coefficient must be positive
3 Modification of Talpha
The reference temperature for the convective heat exchange
4 Modification of sigma
The radiation coefficient must be positive. It is the product of the Stefan-Boltzman constant (5.6697e-8 W/m2/K4 or 5.6697e-5 erg/cm2/s/K4) times the emissivity.
5 Modification of Tsigma
The reference temperature for the radiative heat exchange
6 Modification of T0
A non-vanishing value for T0 must be specified when the temperature scale is not absolute. For example, T0 = 273.15 ?C if temperatures are given in Celsius. This is mandatory when radiative heat exchange is taken into account.

NOTES If large deformations of the (mobile) interface are expected, an evolution scheme must be considered. The recommended approach is to use evolution along moving boundaries.

Every sub-task which has (at least) one kinematic condition on its boundary must have a remeshing rule.

  SEE ALSO