Construct Unstructured Block Assembly with Fidelity Pointwise

With Fidelity Pointwise, one can skin a block, manually or automatically, using structured or unstructured block assembly. In Pointwise, the notion of a “face” is used to define how blocks are assembled. For example, a structured block is defined by six faces, while an unstructured block is defined by at least one outer face and possibly many interior faces (each face can contain multiple domains). Therefore, it is useful to understand the Pointwise block assembly foundation for better decision-making on whether to use manual or automatic block assembly.

Why Use Manual Block Assembly When Automatic Block Assembly Tools Exist?

• Structured Blocks

For structured blocks, manual assembly (what Pointwise calls Assemble Special) will be required when the topology of the block is too complex for the automatic assembly to determine the correct connections between the faces. This can occur when there are multiple domains per face and requires the use of Assemble Special so the user can define each of the six-block faces individually. An indication that the block topology is too complex for automatic assembly is when the Assemble Blocks function on the toolbar simply fails to create the desired block.

Figure 1. Structured block constructed using ‘Assemble Special’.

• Unstructured Blocks

It is easier to decide whether to use automatic or manual assembly for unstructured blocks than it is for structured blocks. If an unstructured block consists of a single closed face, the automatic assembly will be the logical choice. Just select the domains of this face, assuming they are watertight, and click Assemble Blocks from the toolbar, and Pointwise will create an unstructured block. If the block includes more than one face, it must be assembled manually using Assemble Special.

Figure 2. Unstructured block with an internal face.

 

Interior Faces in an Unstructured Block

Additional faces in an unstructured block can serve multiple purposes. The addition of internal, closed faces can be used to designate the boundaries of a physical object within an unstructured block. Interior faces can also serve as an interface between blocks, allowing structured, unstructured, or hybrid blocks to be embedded within the primary flow domain. Such embedded blocks allow for explicit grid point distribution control in critical regions, such as the large wake region behind a vehicle.

Figure 3. Sedan wake region.

Non-manifold interior faces, called baffles, can also be used to add internal topology to an unstructured block. A baffle can be free floating or connected to other baffles and closed faces. Similar to internal, closed faces, baffles can be used for explicit grid point control and can even be used to represent thin walls, like the wings of an insect, shown in Figure 3.

Adding a Face to an Existing Block

For more precise control of the grid, for example, in the downstream wake of the insect, it is possible to add a baffle face without going through the block assembly process again. The user can add faces to an existing block using the Add Face command from the Edit menu. In fact, if a block was constructed from only the outer domains, all interior faces could be added in this manner. One thing to keep in mind is that the addition of a face to a preexisting block causes the block interior to be emptied, thus requiring that the block be reinitialized.

Figure 4. Using a baffle for local grid point control.

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Watch the Youtube video below to learn how the Assemble Special feature in Fidelity Pointwise can be used to add faces to an unstructured block.

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For more information about unstructured block assembly, read There's More Than One Way to Skin a Block – Tips on Unstructured Block Assembly Using Assemble Special by clicking the button below -