Rotating Frame
Centrifugal, Coriolis, and Euler forces are “fictitious” volume forces that need to be introduced in a rotating frame of reference, since it is not an inertial system. Use a Rotating Frame node to add the effect of these forces. The forces are generated by all selected features in the physics interface having a density, mass, or mass distribution. You select objects having the highest geometrical dimension of the interface, and all objects with a lower dimensionality which belong to the selection are automatically included.
The idea when using a rotating frame is that the observer rotates with the structure. All results, such as displacements are thus relative to the rotating frame.
The Rotating Frame node is only available with some COMSOL products (see http://www.comsol.com/products/specifications/).
Shell Properties

Rotating Frame
Select an Axis of rotationx-axis, y-axis, z-axis, or User defined. For User defined enter a Rotation axis base point rbp and Rotation axis direction eax.
Select a Rotational direction Counterclockwise or Clockwise. The rotational direction does not make any difference for a centrifugal force.
Select a Rotational frequency Angular velocity magnitude, Revolutions per time, or User defined.
For Angular velocity magnitude enter a value for the angular velocity magnitude Ω.
For Revolutions per time, enter an RPM value.
For User defined, enter the Rotation angle α in radians as function of time (the variable t).
In the case of a geometrically nonlinear analysis, the displacements computed in the Solid Mechanics interface are used to defined the spatial frame. When a rotating frame is used, there are two possible interpretations.
Select Define spatial frame rotation to add also the rotation to the definition of the spatial frame. For other physics interfaces, this is similar to specifying a Rotating Domain, but with the displacements added. This approach must be used if there are a mix of stationary and rotating domains.
When Define spatial frame rotation is selected, the actual angle of rotation becomes important. If the angular speed is non-constant, you must then enter an expression for the angle as function of time explicitly using the User defined option. For the two other input options, the angle of rotation is assumed to be α0 + Ωt.
Frame Acceleration Effect
For 3D and 2D components, use the Centrifugal force, Coriolis force, or Euler force check boxes to determine which effects of a rotating frame that are to be incorporated in the analysis. Only Centrifugal force is selected by default.
For 2D axisymmetric components, the only effect from a rotating frame is the centrifugal force, which is then always included.
The Spin softening check box is selected by default. When including spin-softening effects, an extra contribution to the centrifugal force from deformation is taken into account. The Spin softening check box is only available if Centrifugal force or Euler force is selected.
Only features which have a geometrical selection contribute to the mass forces. The Mass and Moment of Inertia nodes are global features and will not get any contribution from Rotating Frame.
Location in User Interface
Context Menus
Ribbon
Physics tab with Solid Mechanics or Multibody Dynamics selected:
Physics tab with Shell, Layered Shell, or Membrane selected:
Physics tab with Plate selected:
Physics tab with Beam or Truss selected: