Description

The Build Refinement, Unstructured command is designed to quickly create unstructured refinement blocks used as background and transition blocks in overset grid topologies. Please refer to the Grid, Overset command, for more information regarding overset tools.

The selected entities will be queried for grid spacings which in turn can be used to determine a homogeneous spacing for the new unstructured block. Refer to the Spacing Controls section below for more information on setting spacings. Note that the selected entities are not used to form the faces of the new block; only their spacings are used for reference.

Build Refinement Panel: Unstructured
Use the commands in the Build tab to quickly create unstructured block topology based on existing grid entities.

At the top of the Build Refinement panel, you will find a table displaying the X, Y, and Z Characteristic Length of the selected entities. Additionally, the Minimum, Average, and Maximum spacings of the size field and the estimated boundaries of the new block are shown. Keep in mind that the size field is computed considering the initial selected entities, any enabled sources, and any additional grid entities marked as size field influencers in the Size Field tab.

Block Type

The Block Type frame (shown above with the Untructured option circled in red) allows you to choose the block type to be created: Structured, Unstructured, or Voxel. When you enter the Build Refinement panel for the first time, the Block Type will be selected directly via the menu. If the toolbar option was used, the toolbar icon updates to the last block type used for quick access to the command and type.

Shape

In the Shape frame (shown below), you can set up a symmetry plane definition for the new block as well as its extents. By default for Symmetry Planes, the Automatic toggle is checked on. This means that the command will try to determine a single or two planes of symmetry automatically from the selected grid entities. If a symmetry plane is not detected automatically, you can use the first and second pull-down lists to select it manually. Note that using one of the two pull-down lists will uncheck the Automatic toggle automatically. You can recheck this toggle to have the panel restore the automatically detected symmetry plane(s).

In the Margins frame, you will find fields to set the extents of the new block in the X, Y, and Z coordinates. The Uniform text field allows you to enter a single number which will be used in all three coordinate directions. This value will automatically populate the individual coordinate direction fields just below (i.e. +X, -X, +Y, -Y, +Z, and -Z). The individual fields can also be used to enter unique numerical values for each coordinate minimum and maximum.

Use the Shape frame to specify the extents of the new block.
Use the Shape frame to specify the extents of the new block.

Spacing Controls

The Spacing Controls frame shown below provides controls to specify how the Boundary Spacing is determined, a Decay value, and a Background Spacing. Two choices are available for Boundary Spacing: Variable From Size Field and Constant From Size Field. Variable From Size Field uses the influence of the selected domains, any sources located inside a region computed as twice the size of the block's bounding box, the Decay, and the Background Spacing to set boundary cell sizes locally.

Use the Spacing frame to specify the cell sizing of the new block.
Use the Spacing frame to specify the cell sizing of the new block.

Constant From Size Field will use the Minimum, Average, or Maximum spacing from the selected domains. Once this Boundary Spacing option has been selected, Size Field Spacing is added to the command frame (shown below) with these three choices, Minimum being the default.

Constant From Size Field adds the Size Field Spacing choices of Minimum, Average or Maximum to the frame.
Constant From Size Field adds the Size Field Spacing choices of Minimum, Average or Maximum to the frame.

Decay defaults to whatever value is specified in the Defaults panel, where 0.5 is the default. Uncheck Use Default to enter a new value. Background Spacing is determined automatically from the selected domains cell sizes, Decay and Margins of the block. Uncheck Use Default to enter a new value in the text field.

Finally, you can click Update Grid Entities at the bottom of the panel to preview the bounding domains of the pending new block. If size field refinement or boundary adaption will be necessary, the Solve command for unstructured blocks will need to be used. If desired, tools in the collapsed Selection frame will provide a selection mode to reselect the domains to be used by the new block. This would be equivalent to clicking Cancel to exit the command, changing your selection, and entering Build Blocks again.

Update and Selection commands
Use the Update Grid Entities command to preview the pending block boundaries. Additionally, use the commands in the Selection frame to update your initial entity selection.

When the new block is complete, click OK to save it and close the panel, click Cancel to discard it and close the panel, or click Apply to save it and continue on to creating another block.

Demonstration