Applying Initial Velocities

You can define an initial velocity to specify the instantaneous velocity of a structure or fluid at the start of a simulation.

For a body in a structural simulation, an initial velocity prescribes a linear translational velocity and/or an angular velocity about a specified axis/line. Unlike a velocity load, which typically ramps up in magnitude over the course of a step, an initial velocity is applied instantaneously at the start of the simulation.

For a fluid in a flow simulation, an initial velocity prescribes the velocity of the fluid movement in a specified region.

This task shows you how to:

See Also
About Initial Velocities
In Other Guides
Support Selection

Apply Initial Velocities to Structures

  1. From the Initial Conditions section of the action bar, click Initial Velocity .
  2. Optional: Enter a descriptive Name.
  3. Select the geometry supports in the model.

    You can apply an initial velocity to one or more structural bodies. You can also select a coupling connection, rigid body, or rigid surface; the velocity is applied to the reference point for the feature.

  4. Optional: Select Specify translation to define a linear initial velocity in the X-, Y-, or Z- direction.
    1. Select an Axis system definition:

      Option Description
      Global Aligns the local feature triad with the global coordinate system.
      Local Aligns the local feature triad with a selected axis system in the model.
      Specify Orients the local feature triad directly by selecting an orientation tool from the context toolbar.
      Implicit Aligns the axis system to the transformed axis system applied on the support.

    2. Select the Degree of freedom that represents the linear direction of the velocity.

      This direction is interpreted in the context of the chosen axis system definition.

    3. Enter the magnitude of the linear Velocity.
  5. Optional: Select Specify rotation to define an angular initial velocity around a chosen line.
    1. Select the line or axis about which the rotation will occur.

      You can select a geometric edge in the model or an axis in a user-defined axis system.

    2. Enter the magnitude of the Rotational velocity.
  6. Click OK.

Apply Initial Velocities to Fluids

  1. From the Initial Conditions section of the action bar, click Initial Velocity .
  2. Optional: Enter a descriptive Name.
  3. Select the geometry supports in the model.

    You must apply an initial velocity to one or more fluid domains. You can click the glyph in the model to select the fluid domain.

  4. Specify the magnitude of the initial velocity vector in the X, Y, and Z-directions for the selected axis. You can specify each component of the initial velocity vector as follows:
    OptionDescription
    Uniform value Initial velocity is constant throughout space in the selected direction.
    Mapped spatial data Initial velocity varies in space according to a table of spatially varying mapped data. For more information, see About Mapped Data.
  5. Select one of the following as the Axis system definition:
    OptionDescription
    Global Aligns the local feature triad with the global coordinate system.
    Local Aligns the local feature triad with a selected axis system in the model.
    Specify Orients the local feature triad directly by selecting an orientation tool from the context toolbar.
  6. Click OK.