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Chapter 8: Rotating Structure Analysis

In a dynamic analysis involving a rotating structure, ANSYS can take inertia effects into account. The following topics related to rotating structure analysis are available:

8.1.Understanding Rotating Structure Dynamics

8.2.Using a Stationary Reference Frame

8.3.Using a Rotating Reference Frame

8.4.Choosing the Appropriate Reference Frame Option

8.5.Example Campbell Diagram Analysis

8.6.Example Coriolis Analysis

8.7.Example Unbalance Harmonic Analysis

For additional information, see Coriolis Matrix and Coriolis Force in a Rotating Reference Frame in the

Mechanical APDL Theory Reference.

8.1. Understanding Rotating Structure Dynamics

You can observe inertia effects, applied via the CORIOLIS command, in either a stationary reference frame or a rotating reference frame. In both cases, you specify angular velocity by issuing an OMEGA or CMOMEGA command.

The dynamic equation incorporating the effect of rotation is given by

ɺɺ +

+

ɺ +

=

 

 

 

 

c

where [M], [C] and [K] are the structural mass, damping, and stiffness matrices, respectively.

[Kc] is the spin softening matrix due to the rotation of the structure. It changes the apparent stiffness of the structure in a rotating reference frame (described in Rotating Structures in the Mechanical APDL Theory Reference).

[G] is a “damping” matrix contribution due to the rotation of the structure. It is usually called Coriolis matrix in a rotating reference frame, and gyroscopic matrix in a stationary reference frame (described in Rotating Structures in the Mechanical APDL Theory Reference).

{F} is the external force vector in the stationary reference frame. In a rotating reference frame, it is the sum of the external force and the effect of the angular rotational velocity force (as described in Acceleration Effect in the Mechanical APDL Theory Reference).

Without the inertia effect applied via the CORIOLIS command, ANSYS does not generate the [G] matrix, and the usual effect of the angular rotation velocity specified by the OMEGA or CMOMEGA command applies (as described in Acceleration Effect in the Mechanical APDL Theory Reference). An exception exists, however, involving a nonlinear transient analysis using element MASS21; in this case, the inertia effect due to rotation applied via an IC command (or a D command over an incremental time) is included without having to issue the CORIOLIS and OMEGA or CMOMEGA commands.

Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information

 

of ANSYS, Inc. and its subsidiaries and affiliates.

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