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Turbomachinery CFD analysis often demands a highly accurate flow prediction. The designer is looking for the overall machine performance, as well as for subtle effects such as the change in efficiency for a small change in the geometry of the blade. This places a wide range of demands on the CFD meshing needed for turbomachinery analysis.
Depending on the demands of the analysis, and the balance between computing time and designer time, various meshing strategies may be adopted.
Traditional turbomachinery analysis demands the highest quality mesh for the least number of nodes, which usually translates into a hexahedral meshing strategy. There are two different hexahedral meshing products available: ANSYS TurboGrid and ANSYS ICEM CFD Hexa. ANSYS TurboGrid is a highly customized hexahedral mesh generator specifically for blade passage meshing. TurboGrid is intimately connected to the ANSYS BladeModeler geometry definition, but can also be used to read geometry files directly from other blade design software. Turbogrid has basic geometry preprocessing to intersection blade and hub/shroud geometries, as well as defined periodic cut surfaces and tip clearance. If the blade geometry is particularly complex or involves special detailed 3-D geometry, ANSYS Hexa can be used to create a custom hexahedral blade passage mesh. Both the Turbogrid and Hexa mesh generators are programmable and can run in batch, which is needed when building an automated turbomachinery meshing system.
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ANSYS TurboGrid |
Mesh Resolution at Leading Edge |
Combination of Hexahedral Mesh in Bladed Component and Unstructured Tet/Prism Mesh in Volute |
In many situations an unstructured or hybrid element mesh is desired for turbomachinery analysis, including the blade passages with complex 3-D tip geometries or cooling holes, as well as complex shaped inlet and outlet geometries such as scrolls, inlet ducting, etc. In this case either of the unstructured mesh generators can be used, ANSYS CFX-Mesh or ANSYS ICEM CFD Tetra. These mesh generators are highly automated, can deal with complex geometries and can be used to create turbomachinery component meshes in a highly automated fashion. ANSYS TurboGrid
For large turbomachine analysis, it is desirable to create mesh in logical sections corresponding to the main geometrical components, rather than create one large mesh for the entire machine. This “divide and conquer” strategy is a practical and effective way to simplify meshing of an entire machine such as a complete pump or turbine. Choose the appropriate meshing strategy for each component, and then use the non-matching general grid interface technology in ANSYS CFX to connect the components together into a complete system for analysis.
