The ASM model is not set up in the same way as other multiphase problems. Only one fluid for a variable composition mixture is used in the Domains tab on CFX-Pre. When setting up a problem to run with the Algebraic Slip Model, you should first create a material for the variable composition mixture. For details, see Material Details View: Variable Composition Mixture in the CFX-Pre User's Guide. When setting the thermodynamic state of the mixture, the choice of liquid or gas is not important. When specifying the domain options, define the fluid in Fluids and Particle Definitions... and select the fluid Material.
The continuous phase should be set to Constraint on the
Component Details tab. The remaining phases can be set
to either Algebraic Slip or Transport
Equation. Transport Equations and
Algebraic Slip components can be combined, meaning that
a mixture of components may be present in the continuous phase. At least one
component must be set to Constraint. For any dispersed
phases, choose the Algebraic Slip option.
The Algebraic Slip option can be set to Drag
Force Balance or Slip Velocity. Drag Force
Balance uses the closed relationship for the slip velocity. For details, see
Derivation of the Algebraic Slip Equation in the CFX-Solver Theory Guide.
 | (7–25) |
where the subscript 
refers to bulk quantities and 
refers
to dispersed phase quantities. The drag coefficient 
can be directly specified or the Schiller Naumann model can be
used. In both cases, the mean diameter 
must be specified.
The slip velocity may also be directly specified.
For wall boundaries, there is the option of specifying wall deposition for a
dispersed phase. When deposition is selected for a phase that contacts a wall
boundary, the mass of the particular phase is removed from the calculation and
replaced with the mass of the ballast phase (the component that was selected as
Constraint on the Fluid Models
tab). The deposition rate is determined from the slip velocity of the algebraic
slip component.
As the model makes a number of assumptions, the model will not produce the best results when:
Non-drag forces are significant.
The dispersed phase does not reach terminal velocity quickly (that is, particles with significant mass are present).
For details, see Derivation of the Algebraic Slip Equation in the CFX-Solver Theory Guide.