Defining incident waves

You can model incident wave loading due to external acoustic wave sources. Select InteractionCreate from the main menu bar, and select the source point, the standoff point (for all incident wave loading definitions except for those using the CONWEP model), and the surface. When specifying source points and standoff points, you can select only reference points that are not associated with any other model component. You can create incident wave interactions in the following types of analyses: implicit dynamic, explicit dynamic, direct steady-state dynamic, and subspace-based steady-state dynamic. Incident wave interactions are active only in the steps in which they are created and do not propagate to any of the following steps. If your model includes incident wave interactions, you must edit the model attributes (see below) to specify an acoustic wave formulation for the model.

This task shows you how to:

See Also
Specifying model attributes
Interaction editors
In Other Guides
Acoustic, Shock, and Coupled Acoustic-Structural Analysis
Acoustic and Shock Loads

Context:

For a brief overview of incident wave interactions, see Understanding interactions. For a more detailed discussion, see Acoustic, Shock, and Coupled Acoustic-Structural Analysis, and Incident Wave Loading due to External Sources.

Specify the acoustic wave formulation for the model

If your model contains incident wave interactions, you must edit the model attributes to specify an acoustic wave formulation. You select a scattered wave formulation or a total wave formulation using the procedure described in Specifying model attributes. The formulation that you select applies for all of the incident wave interactions in your model. For more information, see Scattered and Total Wave Formulations.

Define an incident wave interaction

  1. From the main menu bar, select InteractionCreate.

    Tip: You can also create an incident wave interaction using the tool in the Interaction module toolbox.

  2. In the Create Interaction dialog box that appears, do the following:

    • Name the interaction. For more information about naming objects, see Using basic dialog box components.

    • Select the step. You can define an incident wave interaction only during an implicit, explicit, direct steady-state, or subspace-based steady-state dynamic analysis. An incident wave interaction is active only in the step in which it is created.

    • Select the Incident wave type of interaction.

  3. Click Continue to close the Create Interaction dialog box.
  4. Select the incident wave source point by selecting a reference point that is not associated with any other model component. For more information, see Creating a reference point.

    The source point that you select becomes highlighted in red in the viewport.

  5. For all incident wave definitions except for those using the CONWEP model, select the incident wave standoff point by selecting a reference point that is not associated with any other model component. For more information, see Creating a reference point.

    The standoff point that you select becomes highlighted in green in the viewport.

  6. For an incident wave definition of air or surface blast data using the definitions of CONWEP data, click CONWEP (Air/Surface blast) in the prompt area.

    Abaqus/CAE specifies a Definition of CONWEP for this incident wave definition.

  7. Use one of the following methods to select the surface:

    • Use an existing surface to define the region. On the right side of the prompt area, click Surfaces. Select an existing surface from the Region Selection dialog box that appears, and click Continue.

      Note:

      The default selection method is based on the selection method you most recently employed. To revert to the other method, click Select in Viewport or Surfaces on the right side of the prompt area.

    • Use the mouse to select a region in the viewport.

    The surface or region that you select becomes highlighted in magenta in the viewport, and the Edit Interaction dialog box appears.

  8. For all incident wave definitions except for those using the CONWEP model, click the arrow to the Definition field and select an option from the list that appears. For direct and subspace-based steady-state dynamic analyses, you can only specify the fluid pressure time history at the standoff point.

    • Select Pressure to specify the fluid pressure time history at the standoff point.

    • Select Acceleration to specify the fluid particle acceleration time history at the standoff point.

    • Select UNDEX to specify UNDEX bubble data.

  9. In the Wave Data portion of the editor, perform the following steps:
    1. Select an incident wave interaction property. If desired, click to create the interaction property; see Defining an incident wave interaction property, for more information. The following requirements exist:

      • If you selected the Pressure definition, you must select an interaction property with a planar definition or a spherical definition with either an acoustic or generalized decay propagation model.

      • If you selected the Acceleration definition, you must select an interaction property with a planar definition.

      • If you selected the UNDEX definition, you must select an interaction property with a spherical definition and an UNDEX charge propagation model.

      • If you selected the CONWEP definition, you must select an interaction property with an air blast or surface blast definition.

    2. In the Reference magnitude field, enter the reference magnitude used to scale the values given in the amplitude definition.
  10. If you selected the Pressure or Acceleration definition, perform the following steps from the Standoff Point portion of the editor:

    • For an implicit or explicit dynamic analysis, select a Pressure amplitude or an Acceleration amplitude, depending on the time history definition.

    • For a direct or subspace-based steady-state dynamic analysis, toggle on Real amplitude and/or Imaginary amplitude and select an amplitude.

    If desired, click to create a new amplitude; see Selecting an amplitude type to define.

  11. If you selected the UNDEX definition, perform the following steps in the UNDEX Data portion of the editor:
    1. In the Direction cosine of fluid surface normal field, enter the X-component, Y-component, and Z-component of the direction cosine of the fluid surface normal.
    2. In the Initial depth field, enter the initial depth of the UNDEX charge.
  12. If you selected the CONWEP definition, perform the following steps in the CONWEP Data portion of the editor:
    1. In the Time of detonation field, specify the time when the blast occurs in terms of the total time for the entire analysis.
    2. In the Magnitude scale factor field, specify the factor by which you want to scale CONWEP data units to analysis data units.
  13. Click OK to create the interaction and to close the editor.