# Data Tree Description

The Data Tree contains several sub-categories.

## Global

- Problem Description
- Specifies analysis type and equations to be solved in the problem.
- Radiation Parameters
- Specifies global radiation algorithms and parameters.
- Solar Radiation Parameters
- Specifies global solar radiation algorithms and parameters.
- External Code Parameters
- Specifies communication parameters for coupling with an external solid/structural code.
- Particle Trace Code Parameters
- Specifies communication parameters for coupling with AcuTrace (particle tracing module of AcuSolve).
- Auto Solution Strategy
- Automatically creates a solution strategy by issuing all the other commands in this section.
- Advanced Solution Strategy
- Specifies advanced features of solution strategy such as time sequence, time integration and linear solver parameters.
- User Global Data
- Defines and initializes globally accessible data.
- Multiplier function
- Specifies a scalar multiplier function to scale values of other commands and parameters at run time.
- Material Model
- Specifies the properties of the materials to be used in the problem.
- Surface Tension Model
- Specifies surface tension model for free surfaces.
- Contact Angle Model
- Specifies a contact model for free surfaces with surface tension.
- Emissivity Model
- Specifies an emissivity model for the radiation equation.
- Solar Radiation Model
- Specifies a solar radiation model.
- Body Force
- Specifies a collection of volumetric body force terms such as gravity.
- Reference Frame
- Specifies a reference frame for element sets and boundary conditions.
- Flexible Body
- Specifies a solid body for Fluid-Structure Interaction.
- Mesh Motion
- Specifies mesh motion of the nodes.
- Output
- Specifies the nodal data output that is required for post-processing.
- Nodal Initial Conditions
- Specifies the initialization of nodal values at the start of simulation.
- Global Mesh Attributes
- Specifies the mesh size parameters globally.
- Mesh Process Attributes
- Specifies advanced meshing process parameters.
- Zone Mesh Attributes
- Specifies definition of zones for a refined mesh.

Overall, parameters that are independent of the geometry and mesh of the problem are specified in this section.

## Model

- Volumes: This section gives the list of all of the volumes that are available. All of the elements belonging to a particular volume are grouped into a single element set. All of the elements in an element set have the same material model and body force.
- Surfaces: The subsection Surfaces lists all of the surfaces available in which the boundary conditions are specified.

## Periodic Boundary Conditions

Periodic boundary conditions are a set of boundary conditions that are often used to simulate a large system by modeling a small part that is representative of the actual model.

Periodicity can be set between surfaces using AcuConsole.

In the Periodic BC Dialog, you need to specify the two sides to which the periodicity needs to be applied, the type of periodicity and the distance or angle between those sides.

Two different types of periodicity can be set, Translational and Rotational.

- Translational: If Translational is selected, the X-Offset, Y-Offset and Z-Offset options are available. The distance between the surfaces selected as Side 1 and Side 2 has to be specified. You must be careful while specifying this value as it is not just the distance. For example if the X-coordinates of Side 1 is 0.0 m and Side 2 is 5.0 m then the X-Offset will be 5.0m. If Side 1 and Side 2 are reversed then the X-Offset value should be -5.0 m.
- Rotational: If Type is set to Rotational, the axis of rotation and the angle between the sides has to be specified. The axis of rotation can be set by specifying the X, Y & Z coordinates of Point 1 and Point 2. The angle between the surfaces has to be specified in the box next to Angle.

## Mesh Extrusions

Mesh extrusion is a powerful feature that allows the generation of structured mesh in the entire volume or only on the surface.

The mesh on Side 1 will be extruded onto Side 2. Therefore the order of surfaces selected is important.

The Swap button next to Swap Sides is used for interchanging the Side 1 and Side 2 surfaces.