Defining a velocity/angular velocity boundary condition

You can create a velocity/angular velocity boundary condition to prescribe a velocity for the selected degrees of freedom of the selected region's nodes.

Note:

To fix the velocity of a region at zero you must define a specific displacement for that region (see Defining a displacement/rotation boundary condition).

See Also
Using the Load module
Creating and modifying prescribed conditions
Using analytical expression fields
Creating expression fields
In Other Guides
Boundary Conditions
  1. Display the velocity/angular velocity boundary condition editor using one of the following methods:

  2. By default, the global coordinate system is used to define the boundary condition. To change the coordinate system in which the boundary condition is applied, click for the CSYS option and do one of the following:

    • Select an existing datum coordinate system in the viewport.

    • Select an existing datum coordinate system by name.

      1. From the prompt area, click Datum CSYS List to display a list of datum coordinate systems.

      2. Select a name from the list, and click OK.

    • Click Use Global CSYS from the prompt area to revert to the global coordinate system.

    This coordinate system editing option is available only in the step in which the boundary condition is created.

  3. If a Distribution field appears in the editor, click the arrow to the right of the field, and select one of the following:

    • Select Uniform to define a uniform boundary condition.

    • Select User-defined to define the boundary condition in user subroutine DISP. See the following sections for more information:

    • Select an analytical field to define a spatially varying boundary condition. Only analytical fields that are valid for this boundary condition type are displayed in the selection list. Alternatively, you can click to create a new analytical field. (See The Analytical Field toolset for more information.)

    The Distribution option appears in the editor only if you are creating the boundary condition or editing the boundary condition in the step in which it was created. In addition, this option is unavailable if you are performing an Abaqus/Explicit analysis.

  4. If you selected the Uniform or analytical field distribution option, perform the following steps:
    1. Use the appropriate method to define the boundary condition:

      If no text fields appear next to each degree of freedom:

      You can use the following techniques to define the boundary condition:

      • Toggle on a degree of freedom to fix the value at zero.

      • Toggle off a degree of freedom to leave the degree of freedom unconstrained.

      If text fields appear next to each degree of freedom:

      You can use the following techniques to define the boundary condition:

      • Toggle on a degree of freedom to constrain the degree of freedom. The text field becomes available in which you can specify a value for the degree of freedom. If you are creating the boundary condition in this step, a default value of zero appears in the text field. If you are modifying the boundary condition in this step, the value propagated from the previous step appears in the text field.

      • Toggle off a degree of freedom to leave the degree of freedom unconstrained. If you toggle off a degree of freedom after modifying the default or propagated value in the text field, the modified value is lost. If you toggle that degree of freedom back on, the default or propagated value reappears in the text field.

      • Click the arrow to the right of the Amplitude field, and select the amplitude of your choice from the list that appears. Alternatively, you can click to create a new amplitude. (See The Amplitude toolset for more information.)

    2. Click OK to save your data and to exit the editor.
  5. If you selected the User-defined distribution option, perform the following steps:
    1. If desired, use the following techniques to define the velocity:

      • Toggle on a degree of freedom to constrain the degree of freedom. If you are in the initial step, that degree of freedom is set to zero. If you are in any step other than the initial step, a text field becomes available in which you can specify a value for the degree of freedom.

      • Toggle off a degree of freedom to leave the degree of freedom unconstrained.

      Data that you enter in the editor for specific degrees of freedom are passed into the user subroutine.

    2. Click OK to save your data and to exit the editor.
    3. Enter the Job module and display the job editor for the analysis job of interest. (For more information, see Creating, editing, and manipulating jobs.)
    4. In the job editor, click the General tab, and specify the file containing the user subroutine that defines the boundary condition. For more information, see Specifying general job settings.

      Note: You can specify only one user subroutine file in the job editor; if your analysis involves more than one user subroutine, you must combine the user subroutines into one file and then specify that file.