17.6.1.3. Rotational Velocity

Rotational Velocity accounts for the structural effects of a part spinning at a constant rate.

This page includes the following sections:

Analysis Types

Rotational Velocity is available for the following analysis types:
Note:
Modal Analyses

  • Rotational Velocity is valid only when the following Analysis Settings properties are specified:

  • Use Condensed Geometry to include the effects of a Rotational Velocity load processed in a Substructure Generation analysis by importing the condensed part into a Modal analysis. The Modal analysis must have the Coriolis Effect property set to On, Stationary Reference Frame. For this capability, the Imported Condensed Part only supports the Exported Condensed Part (.cpa) file format. Once imported, the application processes the Rotational Velocity during the Use Pass of the Modal analysis. For a standalone Modal analysis or when you link your Modal analysis to either a downstream Harmonic Response or a Transient Structural analysis, the application applies Rotational Velocity in the Modal analysis to compute damped frequencies and as a load vector in the downstream harmonic/transient analysis.

Static Structural Analyses

If Rotational Velocity is defined in a Static Structural analysis, the spin softening effect is automatically included in rotating reference frame dynamics (Coriolis Effect set to Off in the Rotordynamics Controls group). This may lead to negative or zero frequencies in a downstream perturbed Modal analysis. This does not apply to stationary reference frame dynamics (Coriolis Effect set to On, Stationary Reference Frame).

Transient Structural Analyses

For a Transient Structural analysis that is linked to a Modal analysis, Rotational Velocity is an invalid boundary condition in the Transient Structural analysis.

Dimensional Types

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

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

  • 2D Simulation. For 2D axisymmetric simulations, a Rotational Velocity load can only be applied about the y-axis.

Geometry Types

The supported geometry types for Rotational Velocity include:

  • Solid

  • Surface/Shell

  • Wire Body/Line Body/Beam

Topology Selection Options

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

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

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

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

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

  • Two globally scoped (All Bodies) Rotational Velocities may not coexist.

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

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

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

Define By Options

The supported Define By options for the Rotational Velocity 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 Velocity include:

  • Constant

  • Tabular (Time Varying)

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

    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 Velocity Boundary Condition

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

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

To apply a Rotational Velocity:

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

  2. Select a Scoping Method.

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

  4. Define the Magnitude, Component values, Coordinate System, and/or Axis of the Rotational Velocity 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 Velocity 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 the 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

Note:

In a Modal analysis:

  • With multiple solve points (Campbell Diagram turned On), the magnitude or the resultant of the components must be in ascending order.

  • When specified by Components, only the Global Coordinate System is available (the option is read-only).

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

Load Vector Controls (Substructure Generation Analysis Only)

Load Vector Assignment: Read-only property set to Program Controlled. The application automatically sends the Rotational Velocity as the first load vector during Substructure Generation analyses.

Load Vector Number: Read-only property set to 1.

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 CGOMGA command.

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

API Reference

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