Rotating Frame
Use the Rotating Frame feature to exert fictitious forces on particles when computing their trajectories in a rotating frame of reference, including the Centrifugal, Coriolis, and Euler forces.
When this feature is added, the particle trajectories are solved with respect to the rotating (noninertial) reference frame. This means that the dependent variables in the physics interface (particle positions and velocities) correspond to the coordinates in the noninertial reference frame. The corresponding variables in the laboratory (inertial) reference frame are evaluated and are defined as <scope>.qin and <scope>.vin respectively, where <scope> includes the name of the physics interface node.
The Rotating Frame feature does not rotate the geometry in the spatial frame. It instead implicitly accounts for the rotation on the particle dynamics by transforming the reference frame. Therefore, the Rotating Frame feature is best suited for models with rotationally symmetric geometries.
Alternatively, the Rotating Domain feature can be used to model the rotation in complex geometries as it accounts for the rotation via the moving mesh functionality.
The Rotating Frame and the Rotating Domain features therefore should not be used together in the same study step.
Rotating Frame
In 2D, enter the coordinates of the Rotation axis base point rbp (SI unit: m) about which the frame rotates. The default is the origin (0,0).
In 3D, select an option from the Axis of rotation list: x-axis, y-axis, z-axis (the default), or User defined. For User defined, enter the coordinates of the Rotation axis base point rbp (SI unit: m) about which the frame rotates. The default is the origin (0, 0, 0). Then enter the components of the Rotation axis direction eax (dimensionless). The default direction is parallel to the positive z-axis, (0, 0, 1). It is not necessary to enter a unit vector for the axis direction because the expression is automatically normalized.
The remaining inputs are the same for any space dimension.
Select an option from the Rotational direction list: Counterclockwise (the default) or Clockwise. The sense of rotation follows the standard right-hand rule; that is, if you curl the fingers on your right hand in the direction of the rotation, your thumb points in the direction of the axis of rotation (in 3D) or in the positive z direction (in 2D).
Select an option from the Rotational frequency list: Angular velocity (the default) or Revolutions per time. For Angular velocity enter the Angular velocity magnitude Ω (SI unit: rad/s). The default is 0 rad/s. For Revolutions per time enter the Revolutions per time f (SI unit: Hz). The default is 0 rpm.
Enter a value or expression for the Initial angle of rotating frame αfr,0 (SI unit: rad). The default is 0 rad. The rotation angle is computed by solving an ODE for the angle of the rotating frame αfr, which is therefore a state variable and a part of the solution.
By default the Centrifugal force checkbox is selected. This means that the fictitious centrifugal force is exerted on the particles.
By default the Coriolis force checkbox is selected. This means that the fictitious Coriolis force, which arises when the particles have nonzero velocity in the rotating frame, is exerted on the particles.
By default the Euler force checkbox is selected. This means that the fictitious Euler force, which arises when the frame has nonzero angular acceleration, is exerted on the particles.
When the Rotating Frame feature is active, the particle trajectories are solved for in the noninertial reference frame, and thus the field variables present in other physics features such as the velocity field in the Drag Force feature and the electric field in the Electric Force feature should correspond to the field variables in the noninertial reference frame.
When these field variables are taken from another physics interface, the necessary transformations are automatically applied.
Affected Particles
Use this section to exert the fictitious forces on specific particles. The available settings are the same as for the Force node.
Particle Tracing in Rotating Frames
With the CFD Module see Tubular Centrifuge: Application Library path Particle_Tracing_Module/Fluid_Flow/tubular_centrifuge.