Fundamental Eigenfrequency of a Rotating Blade
Application ID: 9288
High rotational speed in rotating machineries can result in centrifugal forces of considerable magnitude. The forces induced by the rotation give rise to two counteracting effects: stress-stiffening and spin-softening (or centrifugal softening). The former is caused by the stationary stress field created by the centrifugal force and acts to increase the stiffness of the body, and so increase its resonance frequencies. At the same time, any radial displacement away from the axis of rotation increases the centrifugal force, while motion toward the axis decreases it. This application shows how the combined effect from stress-stiffening and spin-softening affects the fundamental eigenfrequencies of a blade attached to a rotating shaft. The eigenfrequencies obtained from the model are compared to analytical solutions.
The model also illustrates how to add the effect of Coriolis forces. Furthermore, a parametric study is performed to evaluate the effect of the angular velocity of rotation on the eigenfrequencies of the blade. The result is represented in the form of a Campbell diagram.
This model example illustrates applications of this type that would nominally be built using the following products:
however, additional products may be required to completely define and model it. Furthermore, this example may also be defined and modeled using components from the following product combinations:
- COMSOL Multiphysics® and
- either the Acoustics Module, MEMS Module, Multibody Dynamics Module, or Structural Mechanics Module
The combination of COMSOL® products required to model your application depends on several factors and may include boundary conditions, material properties, physics interfaces, and part libraries. Particular functionality may be common to several products. To determine the right combination of products for your modeling needs, review the Specification Chart and make use of a free evaluation license. The COMSOL Sales and Support teams are available for answering any questions you may have regarding this.