17.6.1.4. Rotational Acceleration

A Rotational Acceleration load applies a constant rotational acceleration to one or more bodies.

This page includes the following sections:

Analysis Types

Rotational Acceleration is available for the following analysis types:

Dimensional Types

The supported dimensional types for the Rotational Acceleration boundary condition include:

  • 3D Simulation. A Rotational Acceleration is applied along a user defined axis to one or more bodies.

  • 2D Simulation: Not supported for 2D axisymmetric simulation. For 2D Plane Stress and Plane Strain simulations, a Rotational Acceleration load can only be applied about the Z-axis.

Geometry Types

The supported geometry types for Rotational Acceleration include:

  • Solid

  • Surface/Shell

  • Wire Body/Line Body/Beam

Topology Selection Options

The supported topology selection options for the Rotational Acceleration boundary condition include:

  • Body. The following requirements must be met, or the application will invalidate your load:

    • A globally scoped (All Bodies) Rotational Acceleration and a globally scoped (All Bodies) Rotational Velocity may coexist.

    • A globally scoped Rotational Acceleration may coexist with a partially scoped Rotational Velocity.

    • A partially scoped Rotational Acceleration may coexist with a globally scoped (All Bodies) Rotational Velocity.

    • Two globally scoped (All Bodies) rotational accelerations may not coexist.

    • A globally scoped (All Bodies) Rotational Acceleration and a partially scoped Rotational Acceleration may not coexist.

    • A partially scoped Rotational Acceleration may not share topology with another partially scoped Rotational Acceleration.

    • When using the Mechanical APDL solver target, a partially scoped Rotational Acceleration may not share topology with partially scoped Rotational Velocity.

    For global scoping, the application uses the DCGOMG command. For partially scoped bodies, the application uses the CMDOMEGA command.

Define By Options

The supported Define By options for the Rotational Acceleration boundary condition include:

  • Vector. While loads are associative with geometry changes, load directions are not.

    The vector load definition displays in the Annotation legend with the label Components. The Magnitude and Direction entries, in any combination or sequence, define these displayed values. These are the values sent to the solver.

  • Components

Magnitude Options

The Magnitude options for Rotational Acceleration include:

  • Constant

  • Tabular (Time Varying)

  • Tabular (Step Varying): Supported for Static Structural analysis only.

    Note:  If you establish a step varying tabular load and you deactivate one of the steps, the application will ramp the value of this load to zero across the load step rather than immediately zeroing the value at the first substep.

  • Function (Time Varying)

Applying a Rotational Acceleration Boundary Condition

To apply a Rotational Acceleration to all bodies, in the Details pane, accept the default Geometry setting of All Bodies.

To apply a Rotational Acceleration to selected bodies, in the Details pane, set Scoping Method to either Geometry Selection or Named Selection, then either select the bodies in the Geometry window (hold down the Ctrl key to multiple select) or select from the list of the Named Selections available in the Details pane.

To apply additional Rotational Acceleration loads, you must have applied the original load to selected bodies, per above, not to All Bodies.

To apply a Rotational Acceleration:

  1. On the Environment Context tab, click Inertial>Rotational Acceleration. Alternatively, right-click the Environment tree object or in the Geometry window and select Insert>Rotational Acceleration.

  2. Select a Scoping Method.

  3. Select the method used to define the Rotational Acceleration: Vector (default) or Components.

  4. Define the Magnitude, Component values, Coordinate System, and/or Axis of the Rotational Acceleration based on the above selections.

    Note:  The Axis property is not associative and does not remain joined to the entity(s) selected for its specification. Therefore, the specified axis is unaffected by geometry updates, part transformation, or through the use of the Configure tool (for joints).

Details Pane Properties

The selections available in the Details pane are described below.

CategoryProperty/Options/Description
Scope

Scoping Method: Options include:

  • Geometry Selection: Default setting, indicating that the boundary condition is applied to a geometry or geometries, which are chosen using a graphical selection tool.

    • Geometry: Visible when the Scoping Method is set to Geometry Selection. Displays the type of geometry (Body) and the number of geometric entities (for example: 1 Body, 2 Bodies) to which the boundary has been applied using the selection tools.

  • Named Selection: Indicates that the geometry selection is defined by a Named Selection.

    • Named Selection: Visible when the Scoping Method is set to Named Selection. This field provides a drop-down list of available user-defined Named Selections.

Definition

Define By: In a cyclic symmetry analysis, the Rotational Acceleration must be defined by components. Options include:

  • Vector: A magnitude and directional axis (based on selected geometry). Requires the specification of the following inputs:

    • Magnitude

    • Axis

  • Components: Requires the specification of the following inputs:

    • Coordinate System: Drop-down list of available coordinate systems. Global Coordinate System is the default. When using cyclic symmetry, the referenced coordinate system must match coordinate system used in the Cyclic Region. The referenced coordinate system must be Cylindrical.

    • X Component: Defines magnitude in the X direction.

    • Y Component: Defines magnitude in the Y direction.

    • Z Component: Defines magnitude in the Z direction.

    • X Coordinate

    • Y Coordinate

    • Z Coordinate

Suppressed: Include (No - default) or exclude (Yes) the boundary condition.

Mechanical APDL References and Notes

The following Mechanical APDL commands and considerations are applicable for this boundary condition.

  • For global scoping, the application uses the DCGOMG command.

  • For partially scoped bodies, the application uses the CMDOMEGA command.

API Reference

For specific scripting information, see the Rotational Acceleration section of the ACT API Reference Guide.