Ansys Meshing Application培训9.pptVIP

Mesh Quality Considerations for CFX The CFX solver calculates 3 important measures of meshquality at the start of a run and updates them each time themesh is deformed Mesh Orthogonality Aspect Ratio Expansion Factor Mesh Orthogonality in CFX Orthogonality measures alignment of: ip-face normal vector, n, node-to-node vector, s. Mesh Expansion Factor in CFX Expansion factor measures how poorly the nodal position corresponds to the control volume centroid Mesh Aspect Ratio in CFX Significance of Mesh Quality in CFX Sources of discretisation error non-orthogonality introduces errors in flux approximations large mesh expansion introduces errors in storage and source approximations Amplification of discretisation error corrections to reduce errors caused by non-orthogonality can create unphysical influences Difficulties solving linearised equations large aspect ratios require use of more significant digits(i.e. use of double precision solver) Edit the Mesh Edit the Mesh (cell A3) The Meshing window will open Start by suppressing the fluid region and meshing the solid: Select the Body selection icon from the toolbar Select the inner fluid region, sothat it is highlighted in green, andthen right-click and selectSuppress Body Mesh Settings Select Mesh from the Outline tree In the Details view set the Physics Preference to CFD The assumption here is that heat transfer will be solved in the solid region using a CFD solver Examine the Mesh The Patch Conforming method meshes each individual surface. This produces a poor quality mesh on some surfaces in this geometry. Examine the surface mesh and look for regions of poor mesh quality. By switching between Geometry and Mesh in the Outline tree relate regions of poor mesh quality to the underlying surface geometry. Some examples are shown here: Adding Virtual Topology Virtual Topology allows you to merge adjacent surfaces, removing undesirable surface geometry feature and producing a higher quality mesh Right-cl