Static Bodies

General Concepts

Static Bodies are fixed, non-deformable geometries that act as walls for fluids, particles, bubbles, and/or species. Static Bodies are characterized by a parent-child relationship. Within this relationship, the parent defines the global properties/boundary conditions uniformly assigned to a set of children. The children define the shape/geometry/topology of the solid surface with the boundary conditions defined by the parent. Parents define the properties, children define where these properties will be applied.

Importing Static Bodies

A Static Geometry parent is defined under the Geometry->Add Static Body menu command. Upon import, users will be asked to define the first child geometry. Users have two options for defining child geometry:

  1. Import from File, or

  2. Create Parametric.

Import from File

The Import from File option prompts the user to open either a STL, STEP, or IGES file (Manifold Solid [type 186]) containing a solid model of the child geometry. The CAD geometry need not contain continuous components, as objects like dip tubes, heating coils, or baffles may be disconnected from the general geometry body. Upon import, the local origin of any imported geometry will be placed coincident with the global simulation origin.

Create Parametric

This option allows users to build simple tank, pipe, cylinder, and box children geometries directly within the GUI. Users can also interactively modify the dimensions and parameters of these objects.

Any number of children geometry can be added to the static boundary parent. These children can be a heterogeneous mixture of imported CAD and parametric geometry.

Positioning Static Bodies


Parents can be named, rotated, translated and scaled by right-clicking on the object in the model tree. A transformation to the parent affects all children equally. The position and orientation of the parent (relative to the simulation basis) is reported in the property grid.


Children can be rotated, translated, scaled and colored independently of any parents and siblings. The position and orientation of the child (relative to the simulation frame) is reported in the property grid. The position of all children is defined relative to the global origin.

Parent Properties and Operators


Contact angle, [degrees]

Used to quantify the wettability of the children geometry via the Young equation

Boundary type, [Bounce Back, Off-lattice]

Static bodies can be modeled using either (i) an on-lattice voxelized approach, or (ii) an off-lattice, interpolated approach.

In the on-lattice voxelized approach, any fluid lattice element that intersects the static geometry is assigned a no-slip, bounce-back wall boundary condition. This approach is ideal for flat, lattice-aligned walls. Any curved surfaces, however, will follow a stair-step contour with a step height equal to the local lattice spacing.

For the off-lattice interpolated approach, fluid lattice elements are not explicitly redefined. Rather, the effects of the wall on the fluid are extrapolated onto the fluid as a function of distance from the wall. For curved or non-grid-aligned surfaces, the off-lattice interpolated approach can provide a superior representation of the boundary. With increasing resolution, however, the difference between these two approaches diminishes.

For the on-lattice approach, the wall is assumed to have zero velocity. With off-lattice interpolated boundary conditions, users have the option to impose a non-zero wall velocity. Options are presented to define a constant translational velocity or a constant angular velocity (about a user-defined axis of rotation).


Add Geometry

Add new child geometry to the parent


Translate entire static body family about a user-defined displacement vector


Rotate entire static body family about a user-defined rotation vector


Volume scale the entire static body family about a user-defined anchor point


Rename the parent. This name will persist to the output files.


Delete the parent and all children.

Child Properties and Operators

Location, [model units]

Used to define the position of the child geometry in the global Domain

Orientation, [-]

Unit vector describing the orientation of the local basis vectors, with respect to the global x, y and z basis.

Visible, [on, off]

Chose to render the child in the 3D view window

Transparency, [-]

Set the rendering transparency of the child geometry

Color, [-]

Set the color of the child geometry

Mode, [Shaded, Wireframe]

Set the representation of the child geometry

Material, [-]

Set the material representation of the child geometry in rendered viewed