7.10. Centripetal Force

BEGIN CENTRIPETAL FORCE
  NODE SET|NODESET = <string list>nodelist_names
  SURFACE|SIDESET|SIDE SET = <string list>surface_names
  BLOCK = <string list>block_names
  ASSEMBLY = <string list>assembly_names
  INCLUDE ALL BLOCKS
  REMOVE NODE SET = <string list>nodelist_names
  REMOVE SURFACE = <string list>surface_names
  REMOVE BLOCK = <string list>block_names
  #
  CYLINDRICAL AXIS = <string>cylindrical_axis
  ROTATIONAL VELOCITY FUNCTION = <string>rotational_vel_name
  ROTATIONAL VELOCITY SCALE FACTOR = <real>rvsf(1.0)
  FORCE SCALE FACTOR = <real>fsf(1.0)
  ACTIVE PERIODS = <string list>period_names
  INACTIVE PERIODS = <string list>period_names
END [CENTRIPETAL FORCE]

The centripetal force boundary condition adds an external force to the body that is equivalent to the centripetal force on the body rotating at the defined rotational velocity. The centripetal force boundary condition can be used, for example, in a static analysis to calculate the deformation of a body spinning with constant rotational velocity around some axis.

The centripetal force boundary condition will be applied to all nodes selected within the command block. The equation for the centripetal force on a node is given by (7.2), where \(F\) is the magnitude of the centripetal force, \(m\) is the mass of the node, \(R\) is the current distance from the node to the rotational axis, and \(\omega\) is the rotational velocity of the node about the rotational axis.

(7.2)\[F = m R \omega^2\]

The CYLINDRICAL AXIS command defines the name of the axis of rotation. The name given is the name of a previously defined axis created with the DEFINE AXIS command. The rotational velocity as a function of time is defined by multiplying the function named by the ROTATIONAL VELOCITY FUNCTION by the ROTATIONAL VELOCITY SCALE FACTOR. Additionally a scale factor on the final return force may be specified with he FORCE SCALE FACTOR command.

Assemblies may contain blocks, surfaces, nodesets, or assemblies of these.