To specify a mass concentration:

1. Display the mass concentration boundary condition editor using one of the following methods:

   • To create a new mass concentration boundary condition, follow the procedure outlined in “Creating boundary conditions,” Section 16.8.2 (Category: Other; Types for Selected Step: Mass concentration).

   • To edit an existing mass concentration boundary condition using menus or managers, see “Editing step-dependent objects,” Section 3.4.13. To edit the region to which the boundary condition is applied, see “Editing the region to which a prescribed condition is applied,” Section 16.8.4.

2. If a Method field appears toward the top of the editor, click the arrow to the right of the field, and select one of the following:

   • Select Specify magnitude if you want to specify a value for the mass concentration.

   • Select Fixed at current magnitude if you want to fix the mass concentration magnitude at its final value from the previous general step.

   The Method option appears in the editor only if both methods are valid for the selected step.

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:

     • “Specifying general job settings,” Section 19.8.6

     • “DISP,” Section 1.1.4 of the Abaqus User Subroutines Reference Guide

   • 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 Chapter 58, “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. This option is unavailable if you select the Fixed at current magnitude method.

4. If you selected the Uniform or analytical field distribution option, perform the following steps:

   1. If applicable, enter the mass concentration magnitude in the Magnitude field.

   2. If applicable, 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 Chapter 57, “The Amplitude toolset,” for more information.)

      Note:  The Magnitude and Amplitude fields are unavailable if you are creating the boundary condition in the initial step (in which case the magnitude is always zero) or are fixing the magnitude at the final value from the previous general step.

   3. 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, enter the mass concentration magnitude in the Magnitude field. Magnitude data that you enter in the editor are passed into the user subroutine.

      (The Magnitude field is unavailable if you are creating the boundary condition in the initial step.)

   2. Click OK to save any entered 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,” Section 19.7.)

   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,” Section 19.8.6.

      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.