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[FAQ]

For certain geometries in TurboGrid, too many layers layers can be created. The resulting span-wise interpolation can then generate negative element volumes. The workaround is to turn off automatic intermediate layer creation, delete extra layers, and perhaps switch to linear span-wise interpolation. The instructions for these steps are: 1. Double click on Layers in the tree outline. Change “Intermediate Layers Insertion Mode” from “Automatic – Adaptive” to “Manual”. 2. Delete the first couple of layers from the hub so that the first layer off the hub is at ~0.25 span fraction. 3. Double click on Layers in the tree outline. Change “Spanwise Mesh Interpoloation Guide Curves” from “Automatic” to “Piece-wise linear”. Further Notes: It is known that the TurboGrid Automatic Insertion of layers does not always work as you would expect. The insertion tolerance has a dependence on the blade shape, blade thickness and ATM topology selected. If there are any changes in these, then TurboGrid will not be consistent in how many layers it will insert. When preparing new cases for comparing to an existing design, it’s best to start with the same TurboGrid state file with the automatic layer insertion turned off. That will minimize mesh changes from one case to the next. To do this in Workbench, turn off automatic layer insertion (see 1. above), then copy the TurboGrid system and connect it with the new design. Furthermore, under Mesh Data you can choose the option “Lock mesh size” to limit the mesh size changes that are based on blade geometry.