Reference Concentration = CONSTANT <species> <float> 
Description / Usage#
This required card is used to specify the model for the reference concentration, which is required by the BOUSS option on the Navier-Stokes Source card. Definitions of the input parameters are as follows:
Model for a constant reference concentration.
The following is a sample input card:
Reference Concentration = CONSTANT 0 0.
The Boussinesq model subtracts out the pressure head in its final equations. Thus, to zeroth order, hydrodynamic pressure field doesn’t include a static variation in the gravity direction due to the pressure head. But, the source term in the momentum equations then becomes –g(ρ – ρo) instead of simply –gρ. The reference concentration values entered via this card are used to evaluate ρo for use in calculating the natural convective force due to concentration differences.
The card is also used in various places where a value for a species concentration is needed. However, the species unknown variable is not included in the solution vector.