### 18.1.4. Initial Conditions Tab

The Initial Conditions tab contains settings for initializing the rigid body solver. These settings are described in the following subsections.

Note: These settings are not available for rigid bodies defined as immersed solids.

Note: For the settings on the Initial Conditions tab, the Automatic option provides initial values of zero, and the Automatic with Value option provides initial values as specified. In both cases, the values used at the beginning of a restarted run are taken from the results of the previous run. When you restart a run, select Continue History From and choose initial values from the previous results. To access this option, you should be in the Define Run dialog box of CFX-Solver Manager and both Initial Values Specification and Continue History From must be selected.

#### 18.1.4.1. Center of Mass

These settings define the location (in the rigid body coordinate frame) of the center of mass of the rigid body at the start of the simulation. These settings should be set with non-zero values only if the origin of the rigid body coordinate frame is not at the center of mass of the rigid body at the start of the simulation. If non-zero values are required, then they represent the translation from the origin of the rigid body coordinate frame to the position of the rigid body center of mass at the start of the simulation.

Note: Setting non-zero values for the Center of Mass settings does not impose a mesh motion at the start of the simulation; rather, the initial position of the mesh is assumed to represent the physical location of the rigid body at the start of the simulation.

Note: It is recommended that you define a rigid body coordinate frame that has its origin located at the initial center of mass of the rigid body (that is, the center of mass of the rigid body as positioned in the initial mesh). You could then set all the Center of Mass settings on the Initial Conditions tab to zero (or select the Automatic option to set the initial values to zero automatically).

#### 18.1.4.2. Linear Velocity

These settings initialize the translational velocity of the rigid body in the rigid body coordinate frame. The velocity components are taken as being along the principal axes of the rigid body coordinate frame.

#### 18.1.4.3. Angular Velocity

These settings initialize the angular velocity of the rigid body in the rigid body coordinate frame. The angular velocity components are taken as being about the principal axes of the rigid body coordinate frame, using the right-hand rule to establish direction.

#### 18.1.4.4. Linear Acceleration

These settings initialize the translational acceleration of the rigid body in the rigid body coordinate frame. The acceleration components are taken as being along the principal axes of the rigid body coordinate frame.

#### 18.1.4.5. Angular Acceleration

These settings initialize the angular acceleration of the rigid body in the rigid body coordinate frame. The angular acceleration components are taken as being about the principal axes of the rigid body coordinate frame, using the right-hand rule to establish direction.

Release 18.2 - © ANSYS, Inc. All rights reserved.