Rotating Boundary
Use the Rotating Boundary node () on boundaries of a Deforming Domain that is expected to be rotating. You can specify the rotation type and the rotation axis.
Rotating Boundary conditions are always enforced as pointwise constraint on the entire feature selection. There are therefore no Excluded Edges, Excluded Points or Constraint Settings sections. The Settings window for the Rotating Boundary node contains the following sections:
Rotation
From the Rotation type list, choose a type of rotation for the domain.
•
Choose User defined (the default) to add a user-defined expression for the rotation angle α in the Rotation angle field.
•
Choose Specified rotational velocity to define a rotational velocity expression of one of the following Rotation velocity expression types:
-
Choose Constant angular velocity to specify an angular velocity ω in the Angular velocity field (SI unit: rad/s) using only numbers and model parameters. Specify an initial angle α0 in the Initial angle field (SI unit: rad). This effectively sets the rotation angle to α=α0+ωt.
-
Choose General angular velocity to specify a general angular velocity ω using an expression in the Angular velocity field (SI unit: rad/s) with an initial angle α0 specified in the Initial angle field (SI unit: rad). The rotation angle is computed by solving an ODE for α, which is therefore a state variable and part of the solution.
-
Choose Constant revolutions per time to specify a revolution frequency f in the Revolutions per time field (SI unit: 1/s) using only numbers and model parameters. Specify an initial angle α0 in the Initial angle field (SI unit: rad). This effectively sets the rotation angle to α=α0+2πft.
-
Choose General revolutions per time to specify a general revolution frequency f using an expression in the Revolutions per time field (SI unit: 1/s) with an initial angle α0 specified in the Initial angle field (SI unit: rad). The rotation angle is computed by solving an ODE for α, which is therefore a state variable and part of the solution.
•
Choose Rigid body to specify that the rotating domain behaves as if attached to a rigid body with the following parameters:
-
Enter an Applied moment M (SI unit: N·m).
-
Enter a Moment of inertia I (SI unit: kg·m2).
-
Enter an Initial angle α0 (SI unit: rad).
-
Enter an Initial angular velocity ω0 (SI unit: rad/s).
The rotation angle is computed by solving an ODE for α, which is therefore a state variable and part of the solution.
Axis
In this section, define the rotation axis by a base point and an axis:
Enter the base point rax components in the Rotation axis base point fields (SI unit: m).
Enter the rotation axis urot in the Rotation axis fields. In 2D, no rotation axis is specified; it is assumed to point out of the plane, toward the observer.
If you specify a General angular velocity or General revolutions per time, the Rotating Domain feature uses an ODE to integrate the rotation angle in time. This can in some situations negatively affect solver behavior. Therefore, when the rotational velocity is constant, make sure to select Constant angular velocity or Constant revolutions per time.