## 20.2. Equation Class Settings Tab

Equation class settings enable you to control some aspects of the CFX-Solver on an equation class basis. For example, you can set a different time scale or advection scheme as well as convergence control and criteria parameters for each class of equations. This is useful if you suspect a convergence problem is caused by a particular equation class; you can then use a smaller timestep or a more robust advection scheme for that equation class.

- Select the equation class for which to specify settings.

- The settings in this tab are a subset of those found on the Basic Settings tab (see Basic Settings: Common).

  For details, see Timestep Selection in the CFX-Solver Modeling Guide and Advection Scheme Selection in the CFX-Solver Modeling Guide.

The settings you specify on this form will override those on the Basic Settings tab. Any equation classes that are unspecified will use the parameters set on the Basic Settings tab. The number and type of equation classes depends on the specific physics of the problem.

For a free surface simulation, you cannot set the advection scheme for the volume fraction (vf) equation class because the CFX-Solver uses a special compressive advection scheme.

For details, see Controlling the Timescale for Each Equation in the CFX-Solver Modeling Guide.

Release 18.2 - © ANSYS, Inc. All rights reserved.