Topology blocks represent sections of the mesh that contain a regular pattern of hexahedral (hex) elements or an unstructured group of various element types. They are laid out adjacent to each other without overlap or gaps, with shared edges and corners between adjacent blocks, such that the entire domain is filled. By using topology blocks to control the placement of elements, a valid mesh can be generated to fill a domain of arbitrary shape. The topology is invariant from hub to shroud and is viewed on 2D layers that are located at various spanwise stations (see Layers).
The topology for blocks of hexahedral elements should be investigated at various layers (especially the hub and shroud layers) to check its quality since the mesh quality is directly dependent.
Note: To visualize the topology on a layer, turn on the visibility using the visibility check box for that layer in the object selector and ensure that at least one topology visibility setting for the layer is turned on. The Topology Visibility setting controls the visibility of the yellow line segments that outline the topology block edges. For details, see Topology Visibility. The Master Topology Visibility setting controls the visibility of the violet line segments that outline the master topology edges. For details, see Master Topology Visibility.
A key feature of Ansys TurboGrid is the visibility of the surface mesh on the topology. As you adjust the topology, Ansys TurboGrid adjusts the surface mesh in real time so that the true effect of topology changes is visible. To help identify problem areas in the surface mesh before you generate the full 3D mesh, you can visualize mesh statistics on the layers. For details, see Mesh Statistics
Topology blocks contain a number of mesh elements along each side. The mesh elements vary in size across topology blocks in a way that produces a smooth transition within and between blocks. This is accomplished by shifting the nodes ("node biasing"[2]) toward, or away from, certain block edges. The topology blocks are positioned by default so that the mesh element sizes vary as smoothly as possible, given the constraints.
[2] Node biasing is an important aspect of mesh generation because it helps to reduce the number of mesh elements.