Fluid Film Interface

The fluid film interface type is used to join a fluid and a fluid-film region.

It represents the contact surface between two fluids. It has properties, conditions, values, and a pop-up menu.

Modeling

  • The equation for mass conservation is used to calculate the film thickness. The volume and surface area of the film are functions of the thickness. Contributions to mass source or sink come from droplet impingement, film stripping, mass transfer, or user-defined sources.
  • The equation for momentum conservation is based on kinematic and dynamic conditions at the interface between the film and the surrounding fluid (film free surface).
  • The equation for energy conservation is based on contributions to the energy source or sink from droplet impingement, film stripping, or user-defined sources.

Fluid Film Interface Properties

You can use the properties that are listed below to adjust the specifications of a FluidFilm Interface node.

Boundary-0
Indicates the "fixed" side of the interface (Read Only).
Boundary-1
Indicates the "adapted" side of the interface (Read Only).

Vertices from boundary-1 are projected onto boundary-0. The orientation can be swapped through the right-click action Reverse Orientation.

Type
Defines the type of interface. Must be set to Fluid-Film Interface.
Topology
Defines the connection type between the interfaces:
  • In-place—uses the in-place topology.
  • Periodic—uses the periodic topology.
  • Repeating—uses the repeating topology.
Connectivity
Defines how the boundaries on the two sides of the interface are connected. Fluid Film interfaces have Imprinted connectivity type. The imprint connectivity type indicates the interface is within regions that are discretized using the finite volume method. The imprint procedure creates intersected faces.

Fluid Film Interface Values

You can use the properties that are listed below to adjust the specifications of a Physics Values interface node.

Contact Resistance
The value of the resistance to conduction through the interface. It is entered as a scalar profile. If a field function defines the value and the Ignore Boundary Values property on the field function is ticked, the function is computed using data from the cell next to the boundary. The available properties are:
  • Dimensions: specifies the resistance in units of m 2 ⋅ K / W or similar. (Read Only)
  • Method: specifies the input method type from Constant, Field Function, Table, or User Code.
Intersection
Available for all direct interfaces to control the intersection tolerance. The available properties for fluid film interfaces are:
Specify by Part Subgroup
Specifies sub-grouping for contact-mode boundary interfaces to set up independent intersection properties. See also Contact-Mode Boundary Interfaces and 调整交界面相交容差（基于几何的方法）.
The remaining properties depend on the setting for the Direct Intersector property. This property is set on the Interfaces node (see Interfaces Properties):
Geometry-Based (Legacy)
This Direct Intersector option activates:
Topology-Based with Connectivity Imprinted
  • Match Outer Boundary: when activated, indicates that the interface boundaries are expected to fully overlap on large-scale topological features. Activate this option only when you expect a complete match of the two boundaries of an interface.

    By default, this property is deactivated.

  • Projection Tolerance: maximum orthogonal projection distance in terms of a fraction of local element diameter. Places a limit on how the vertices of the adapted side get projected onto the fixed side. In cases where the two interface boundaries are separated by greater distances, you can increase the Projection Tolerance value to get fewer remainder faces.

    By default, the tolerance is set to 0.2.

  • Angle Threshold: maximum angle (deg) by which the intersector identifies large-scale features that are mapped from the adapted side onto the fixed side. To preserve sharper features, specify a smaller Angle Threshold value. If the boundary meshes have spurious defects, you can specify a larger value.

    By default, the value is set to 45 deg.