fluent学习50g的教程十七icepak-05meshing

1、MeshingChoice of three meshers available:Two Hexahedral meshersSuited for most (99%) of electronics cooling applications.Unstructured It can be used for most applications satisfactorilyCartesian Tetrahedral mesher Intended for some complex geometryMust be used for ellipsoids, elliptical cylinders, o

2、r polygonal ductingIcepak automatic meshing: OverviewAll the methods are fully automatedCan generate computational meshes at varying levels of complexity No parameters setParameters defined on an object by object basisAfter meshing, Icepak loads the mesh and checks the key quality measure, and repor

3、ts the minimum value in the message window. If there are cells with poor quality, Icepak will automatically display them.The Key measures are:Face Alignment for HexahedralAspect Ratio for TetrahedralAutomatic meshingFor higher mesh count across an object - use x,y,z countLow and High element size/ra

4、tio to refine around objectsInward height/ratio to refine within an object Outward height to refine mesh away from planar objectsBackground mesh - set Max X, Y, Z sizesUse fluid blocks to refine the mesh locallyExamine mesh using surface plots and cut planesAlways check quality using diagnosticMaint

5、ain sufficient mesh density to capture physicsGenerate First Cut MeshCoarse default options with Max X,Y,Z set to 1/10th or 1/20th of domain sizeRefine the MeshExamine the MeshSolveGenerate new MeshYesNoRe-examine the Mesh OK?Meshing steps and considerations Use coarse mesh for initial solutions and

6、 for observing trends Use suitably refined mesh for final solutionTwo Hexahedral Meshers UnstructuredMesh will follow the geometry Uses all element types to fit the mesh to the geometryBackground mesh is made of hexahedral elementsCartesianMesh will be structured mesh consisting only of hexahedral e

7、lementsStair-step approximations to non-rectangular geometryBoth of these meshers can be used to mesh assemblies separately. This will be discussed in more detail later.Both meshers have the same global and per-object settings.Hexahedral meshingDuring the meshing process for the hexahedral meshers,

8、Icepak uses the separation value to check the model. Icepak calculates the distances between objects in each co-ordinate direction and will align objects where their separation is smaller than the tolerance set.As a rule of thumb, the tolerance should be approximately 1/10th of the smallest dimensio

9、n in the model. This will ensure that any changes in volume will not significantly alter the results.If the separation is set higher than 10%, but less than 50% of the smallest dimension, Icepak will prompt you to eitherStop meshing and change manuallyContinue and change automatically to 10%Ignore a

10、nd continueIf the separation is larger than 50%, Icepak will prompt you to Stop meshingContinue and change automaticallyThe separation can be set either in the meshing panel or in the settings configuration panelChecking during meshingIcepak operates on a “cocooning” methodology Each object is meshe

11、d individually as close to the specifications defined as possibleFirst combines adjacent objects togetherCreates single group of multiple objects to “O” grid together Then creates the background Cartesian meshMax Cell size is controlled by Max x, Max y and Max z valuesCuts out a section of the mesh

12、around the grouped objects and replaces the mesh with an unstructured mesh - the “O”-Mesh regionThis allows for a finer mesh to be generated close to objectsIn open spaces between objects the mesh is tessellated with larger elements Minimize computational costsMeshing is the most critical aspect of

13、CFD modeling: A good mesh is absolutely essential for a good solutionHexa-unstructured meshing methodologyElements of an Icepak meshGlobal Settings - for refining meshDefault Settings - mesher type, background mesh settingsPanels to generate, Display, Check quality, and Export to IdeasHexahedral mes

14、hing: Generation panelMesher TypeHexa-Unstructured, Hexa-Cartesian, TetrahedralUnits to useMax X, Max Y, Max Z Control the size of the largest cell allowable in the background meshInit HeightMaximum height of first cell into the domain on all objects within the modelObject ParamsIndividual parameter

15、s SeparationTolerance used when meshing to remove any small gaps/misalignmentsDefault settingsMax X, Y, ZBy default this is 1/20th of the cabinet dimensions1/10th of the domain size is sufficient for a coarse gridValues smaller than 1/20th domain size is rarely needed and is not mendedThese are not

16、meant to be used to refine the mesh close to objects, but purely to generate a reasonable background meshInit Height mended that you do not set this on large models as it can result in very large mesh countsSeparationIt is mended that you set this to 10% of the smallest dimension in your model for t

17、ypical calculations to prevent any large volume changes occurring that might lead to inaccuracies in the results. mendationsNormal Mesher Provides an acceptable mesh for most situations provided background grid is reasonableCoarse Mesher Provides a coarse mesh “first cut” mesh that can be refined lo

18、callyMesher default settings include: Min elements in fluid gap Minimum number of cells in between adjacent faces of closely spaced objectsMin elements on solid edge Minimum number of cells to be placed on the edge of an objectMax O-grid heightMaximum height of the O-grid region from the surface of

19、an object Min elements in fluid gap = 2Min elements in fluid gap = 3Global settings (1)Maximum Size RatioControls the growth rate of cell size The Growth ratio of elements away from surfaces can be controlled using this setting. Dx2 / Dx1 0.01 can result in poor meshValue 1e-5 can result in Huge meshCells in gap Number of cells between objectsEdge criterionControls placement of elements near object edge Natural size factor (NSF)Specifies smal