The Wall Distance (wd) interface (), found under the Mathematics branch () when adding a physics interface, has the equations and boundary conditions for calculating the distance to walls in fluid-flow simulation using a modified eikonal equation, solving for a dependent variable G that is related to the wall distance. The main node is the Distance Equation node, which adds the distance equation (modified eikonal equation) and provides an interface for defining the reference length scale.

When this interface is added, these default nodes are also added to the Model Builder: Wall Distance, Distance Equation, and Initial Values. A default boundary condition is also added: a homogeneous Neumann condition that does not appear in the Model Builder. Right-click the Wall Distance node to add boundary conditions for walls.

The Label is the default physics interface name.

The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.

The default Name (for the first Wall Distance interface in the model) is wd.

Enter a Smoothing parameter σw in Equation 16-18. The default value is 0.2.

The dependent variable is the Reciprocal wall distance G. You can change its name, which changes both the field name and the variable name. If the new name coincides with the name of another reciprocal distance field in the model, the interfaces share degrees of freedom. The new name must not coincide with the name of a field of another type, or with a component name belonging to some other field.

To display other settings than the element order in this section, click the Show button () and select Advanced Physics Options.