27.2.1 Performing Boundary Adaption

You can perform the boundary adaption in three different ways based on:

• Number of cells: In this case, the distance of a cell from the boundary is measured in number of cells.

• Normal distance: In this case, the cell refinement is based on the normal distance of a cell from the boundary.

• Target boundary volume: In this case, the cell refinement is based on a target boundary volume and growth factor.

You can use any of these methods in the Boundary Adaption dialog box (Figure  27.2.1).

Adapt $\rightarrow$ Boundary...

Figure 27.2.1: The Boundary Adaption Dialog Box

Boundary Adaption Based on Number of Cells

The procedure for performing adaption based on the distance of a cell from the boundary in terms of the number of cells is as follows:

1.   In the Boundary Adaption dialog box (Figure  27.2.1), select Cell Distance under Options, choose the boundary zones near which you want to refine cells in the Boundary Zones list, and click Apply.

  This operation is performed to fill the cell distance variable for each cell to be visualized in Step 2.

2.   (optional) Click the Contours... button to open the Contours dialog box.

(a)   Enable Filled contours, disable Node Values.

(b)   Choose Adaption... and Boundary Cell Distance in the Contours of drop-down list.

(c)   Select the appropriate surfaces (3D only).

(d)   Click Display to see the location of cells with each value of boundary cell distance.

By displaying different ranges of values (as described in Section  29.1.2), you can determine the cell distance of the cells you wish to adapt.

3.   Set the Number of Cells to the desired value.

• If you retain the default value of 1, only those cells that have edges (2D) or faces (3D) on the specified boundary zone(s) (i.e., those cells with a boundary cell distance of 1) will be marked or adapted.

• If you increase the value to 2, cells with a boundary cell distance of 2 will also be marked/adapted, and so on.

4.   (optional) If you want to set any adaption options (described in Section  27.12), click on the Controls... button to open the Mesh Adaption Controls dialog box.

5.   Click Mark to mark the cells for refinement by placing them in an adaption register (which can be manipulated as described in Section  27.11.1), or click Adapt to perform the refinement immediately.

Boundary Adaption Based on Normal Distance

The procedure for performing refinement based on a cell's normal distance from the boundary (i.e., distance of cell centroid from the boundary) is as follows:

1.   In the Boundary Adaption dialog box, select Normal Distance under Options, choose the boundary zones near which you want to refine cells in the Boundary Zones list, and click Apply.

  This operation is performed to fill the cell distance variable for each cell to be visualized in Step 2.

2.   (optional) Open the Contours dialog box by clicking on the Contours... button.

(a)   Enable Filled contours, disable Node Values.

(b)   Choose Adaption... and Boundary Normal Distance in the Contours of drop-down list.

(c)   Select the appropriate surfaces (3D only).

(d)   Click Display to see the location of cells with each value of normal distance.

By displaying different ranges of values (as described in Section  29.1.2), you can determine the normal distance of the cells you wish to adapt.

3.   Set the Distance Threshold to the desired value. Cells with a normal distance to the selected boundary zone(s) less than or equal to this value will be marked or adapted.

4.   (optional) If you want to set any adaption options (described in Section  27.12), click on the Controls... button to open the Mesh Adaption Controls dialog box.

5.   Click Mark to mark the cells for refinement by placing them in an adaption register (which can be manipulated as described in Section  27.11.1), or click Adapt to perform the refinement immediately.

Boundary Adaption Based on Target Boundary Volume

This boundary adaption allows you to produce exponentially larger (or smaller) cells as you get further from the boundaries. The cells are marked for refinement based on the following equation:

where $V_n$ is the cell volume, $V_{\rm boundary}$ is the specified boundary volume ( Boundary Volume), $\alpha$ is the exponential growth factor ( Growth Factor), and $d$ is the normal distance of the cell centroid from the selected boundaries. $V_{\rm boundary}e^{\alpha d}$ is the target volume for a cell.

The procedure for this type of boundary refinement is as follows:

1.   In the Boundary Adaption dialog box, select Volume Distance under Options, set the Boundary Volume and Growth Factor to the desired values, choose the boundary zones in the Boundary Zones list where you want the Boundary Volume to be applied, and click Apply.

  This operation is performed to fill the cell distance variable for each cell to be visualized in Step 2.

2.   (optional) Open the Contours dialog box by clicking on the Contours... button.

(a)   Enable Filled contours, disable Node Values.

(b)   Choose Adaption... and Boundary Normal Distance in the Contours of drop-down list.

(c)   Select the appropriate surfaces (3D only).

(d)   Click Display to see the contours of the target volume.

By displaying different ranges of values (as described in Section  29.1.2), you can determine the normal distance of the cells you wish to adapt.

You can modify the values of the inputs ( Boundary Volume, Growth Factor, and/or Boundary Zones), click Apply in the Boundary Adaption dialog box, and then redisplay the contour plot to visualize the modified target volume distribution.

3.   (optional) If you want to set any adaption options (described in Section  27.12), click on the Controls... button to open the Mesh Adaption Controls dialog box.

4.   Click Mark to mark the cells for refinement by placing them in an adaption register (which can be manipulated as described in Section  27.11.1), or click Adapt to perform the refinement immediately.