參考文稿2021-06學習icemhexa strategies

1、Appendix A Hexa Basic Block StructuresIntroduction to ANSYSICEM CFDMesh insidefilletO-grid is required unless approximating a corner using large mesh sizeBad qualityO-grid necessaryAcceptable qualityBad qualityO-grid necessaryBad qualityO-grid necessaryO-gridSmaller mesh sizes, so O-grid is necessar

2、yAppendix A Basic Block StructuresMesh outside filletQuality is good without an O-gridHowever, an O-grid makes normal grid lines for boundary layer resolutionMesh inside and outside fillet.Combine previous examplesThis method needs large mesh sizeVertex at end of filletThis is not preferable because

3、 quality is lowerThere should be one vertex at the CENTER of every approximate 90 degree bendMesh only in ringMesh in bothSplit any radial edgeDelete center blockInner O-grid block should be smaller than the smallest circle, NOT on the circleAdd O-grid inside curvatureAdd O-grid outside curvatureApp

4、endix A Basic Block StructuresIn general, O-grids are required inside curvature but not outside curvature SplitSplitDelete blocksMesh insidetubeTubes are one-block topologiesSplits can be added for more controlMesh insideand outside tubeMany students mistakenly just split at geometry featuresBad qua

5、lityO-grids can make this work although it is not the preferred topologyBad angleAppendix A Basic Block StructuresWe must use the straight-through split strategy as in the previous example for grid lines to flow with the inner tube Delete blockBad angleAdd O-grid for meshing inside curvatureBlocks s

6、elected for creating O-grid2 splitsSplit for better blocking controlThere are multiple methods of producing the Y-block structureMethod 1Quarter O-gridMove verticesThese may also be called wedge blocks.They can be used to effectively terminate mesh from continuing through the geometryO-grids can be

7、used to make complicated structuresAppendix A Basic Block StructuresMethod 2splitMove verticesCreate blockMethod 3Inside H-grid ( bottom-up)Delete blocks “permanently”2 splitsMove verticesCreate blockCollapse blockMethod 4Inside H-grid (top-down)1st quarter O-grid2nd quarter O-gridMove verticesMetho

8、d 5Create block function (quarter O-grid)123456Appendix A Basic Block StructuresAdd O-grid for roundSince the round is closer to 180 degrees than 90 degrees, having two block corners may be better (one vertex corner for every 90 degrees)Add O-grid for roundA Y-block structure can also be used for a

9、circleUseful for filling the center of geometry that is periodic in multiples of 3Add O-gridMove verticesAdd quarter O-gridMove verticesUsed for meshing a periodic wedge domain with model insideAppendix A Basic Block StructuresMove verticessplitDelete blocks “permanently”Merge verticesCreate blocksA

10、dd more splits for controlMethod 2Method 1O-gridMove verticesDelete blockSplits for more controlMost common volute strategy although there are many other strategiesAppendix A Basic Block StructuresThin thicknesses are easily done with an O-gridFirst block the outsideThen put an O-grid inside all blo

11、cks (add appropriate faces)Delete the inside blocksScan planeResulting blocksMethod 1Method 2Vertex moved slightly off intersection for better angles SplitHalf O-gridO-gridAppendix A Basic Block StructuresDelete 2 blocksMethod 3Using Y-blocksHalf O-gridO-gridDelete blocksMethod 4Leaving small ledgeD

12、elete edge associationIn 3D model, interpolate face associationMethod 5Degenerate blocksStart from method 4 aboveMerge verticesFace interpolation not necessary when merging verticesMethod 6Convert blockStart from method 5 aboveAll triQuad dominantConvert block to free for 2D or swept for 3DMove vert

13、icesAppendix A Basic Block StructuresFilleted wings are easily done with a simple block.The block can be made larger than the wing and an O-grid made inside, or the block can be on the wing and the O-grid made around.O-gridEdge splits to shape edgesFilleted wings are easily done with a block on the

14、wing then add an O-grid aroundKnife-edge wings pose a problem if you collapse.The collapse behind the wing must propagate through the blocking, or invalid elements result in a corner.Mesh region beyond the blade-tip is bad quality This means mesh beyond the blade tip will have the same mesh pattern

15、as on the blade tip, as if the blade were meshed inside.Very low angles and unnecessary mesh density result from a simple collapseSplit out a block larger than the wingAppendix A Basic Block StructuresThe easiest way to block sharp edge wings is to use the O-grid strategy shown previously and simply

16、 make a split down the middle for the sharp edgeMake a split down the middleElement angles get worse as the blade angle gets sharper, so this strategy is only good for larger angled geometry.Best max angle possible = 180 - the blade trailing edge angleSince no collapsing is done, there is no problem

17、 with the mesh quality just beyond the blade tip. This strategy will work for rounded and flat tips (with an additional O-grid at the tip)If the blade is very sharp, you will have to resort to collapsing beyond the trailing edge and use a more complicated strategy shown in the next slides to get goo

18、d mesh beyond the blade tip.Or if a C-grid is desired, also use one of the strategies shown next.Move vertices and shape edgesAppendix A Basic Block StructuresCreate 4 blocksCollapse blocksCollapse blockDelete blocks “permanently”Move vertices3 splitsO-grid with splitAppendix A Basic Block StructuresCollapse blockO-gridIn 3D, convert the block