The Level Set (ls) interface (
), found under the
Mathematics>Moving Interface branch (
) when adding an interface, is used to track moving interfaces in fluid-flow models by solving a transport equation for the level set function. Simulations using the
Level Set interface are always time dependent because the position of an interface almost always depends on its history.
The main node is the Level Set Model feature, which adds the level set equation and provides an interface for defining the level set properties and the velocity field.
When this physics interface is added, the following default nodes are also added in the Model Builder —
Level Set Model,
No Flow (the default boundary condition),
Initial Values, and
Initial Values, Fluid 2. Then, from the
Physics toolbar, add other nodes that implement, for example, boundary conditions. You can also right-click
Level Set to select physics features from the context menu.
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 physics interface in the model) is
ls.
There are two stabilization methods available — Streamline diffusion and
Crosswind diffusion. Both are active by default and should remain selected for optimal performance.
By default, the Level Set interface uses Linear elements. When coupling the physics interface to a fluid flow interface by means of
The Two-Phase Flow, Level Set Coupling Feature, exact conservation of the integral of
ϕ is obtained using the nonconservative form provided that the discretization order of the level set variable is equal to or lower than the order of the pressure.
The dependent variable (field variable) is the Level set variable phi. The name can be changed but the names of fields and dependent variables must be unique within a model.
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