《CFX5.5培训资料》（英文版）Mesh

CFX! Mesh CFX5.5V5.5.1H 2001AEA Technology

CFX 5.5 V 5.5.1H © 2001AEA Technology 7-1 Mesh

CFX! Introduction CFX-5 mesh generator provides Automatic mesh generation Unstructured triangular surface mesh generation Tetrahedral/prismatic volume mesh generation There are three modes of volume meshing in CFX-5 Advancing Front and Inflation(AFD Paving and Isomeshing Volume Mesh Import (vmi Mesh adaption CFX5.5V5.5.1H 2001AEA Technology

CFX 5.5 V 5.5.1H © 2001AEA Technology 7-2 Introduction CFX-5 mesh generator provides: - Automatic mesh generation > Unstructured triangular surface mesh generation > Tetrahedral/prismatic volume mesh generation - There are three modes of volume meshing in CFX-5 > Advancing Front and Inflation (AFI) > Paving and Isomeshing > Volume Mesh Import (VMI) - Mesh adaption

CFX! Surface Meshing Surface meshing 回区 Volume Meshing Delaunay surface meshing Advancing front(AF)surface Advancing Front and Inflation meshing Both methods are well recognized Surface Meshing and have established track records v Delaunay Surface Meshing on industrial problems Advancing Front Surface Meshing Both surface meshes mesh individual surfaces D」上Ac Cancel Default sur face mesher is delaunay surface mesher 7-4 CFX5.5V5.5.1H 2001AEA Technology

CFX 5.5 V 5.5.1H © 2001AEA Technology 7-4 Surface Meshing Surface meshing - Delaunay surface meshing - Advancing front (AF) surface meshing Both methods are well recognized and have established track records on industrial problems Both surface meshers mesh individualsurfaces Default surface mesher is Delaunay surface mesher

CFX! Su urface M eshing af is traditionally slower than delaunay af produces higher quality elements at boundaries af mesher cannot mesh closed surfaces af is less robust on surface meshes with large variation in edge length scale around a surface mesh vertex surfaces with small gaps Delaunay mesh quality is not good on poorly parameterized surfaces Delaunay works on closed surfaces CFX5.5V5.5.1H 2001AEA Technology

CFX 5.5 V 5.5.1H © 2001AEA Technology 7-5 Surface Meshing AF is traditionally slower than Delaunay AF produces higher quality elements at boundaries AF mesher cannot mesh closed surfaces AF is less robust on - surface meshes with large variation in edge length scale around a surface mesh vertex - surfaces with small gaps Delaunay mesh quality is not good on poorly parameterized surfaces Delaunay works on closed surfaces

CFX! Surface Meshing AF VS Delaunay aF Surface mesh Delaunay 7-6 CFX5.5V5.5.1H 2001AEA Technology

CFX 5.5 V 5.5.1H © 2001AEA Technology 7-6 AF .vs. Delaunay Surface Meshing AF Surface Mesh Delaunay

CFX! AFI Mesher Domain based -surfaces can only be meshed if a fluid domain has been defined Can view only surface mesh in CFX-Build Surface and volume mesh automatically generated when definition file Is written The process of setting an element length scale can be viewed as a 3 step process Assign suitable background length scale(global length scale) Override this locally on surfaces and regions close to them This can be done semi-automatically using curvature sensitivity Override the above two(when necessary )using mesh controls CFX5.5V5.5.1H 2001AEA Technology

CFX 5.5 V 5.5.1H © 2001AEA Technology 7-7 AFI Mesher Domain based - surfaces can only be meshed if a fluid domain has been defined Can view only surface mesh in CFX-Build Surface and volume mesh automatically generated when definition file is written The process of setting an element length scale can be viewed as a 3 step process - Assign suitable background length scale (global length scale) - Override this locally on surfaces and regions close to them > This can be done semi-automatically using curvature sensitivity - Override the above two (when necessary) using mesh controls

CFX! Mesh parameters Setting mesh parameters Volume mesh spacing oject: Mesh Para Maximum edge length- background scale Reset defaults used everywhere unless volume mesh spacing overridden Maximun Edge Length 00406356 Surface mesh spacing Use volume spacing -use background Use volume spacing length from volume meshing Adjust meshing spacings Angular resolution- curvature sensitive Tarcet Number of Node Relative error-curvature sensitive 厂 Apply Stretch Constant-constant length scale on all surfaces Proximity Target number of nodes to adjust grid spacing sUrface Stretch factors for stretching grids Apply proximity CFX5.5V5.5.1H 2001AEA Technology

CFX 5.5 V 5.5.1H © 2001AEA Technology 7-9 Mesh Parameters Setting mesh parameters - Volume mesh spacing - Maximum edge length - background scale - used everywhere unless overridden - Surface mesh spacing > Use volume spacing - use background length from volume meshing > Angular resolution - curvature sensitive > Relative error - curvature sensitive > Constant - constant length scale on all surfaces - Target number of nodes to adjust grid spacing - Stretch factors for stretching grids - Apply proximity

CFX制 Curvature sensitive mesh Surface mesh parameters Value(degrees)-code chooses edge Action: Mesh Param length such that the set angle is subtended at the centre of circle with radius equal to set defaults spacing smallest radius of curvature default is 18 「o406356 degrees(recommended 5 to 60 degrees) Surface mesh spacing Value(fraction )-deviation of mesh from Angular resolution T surface as a fraction of local minimum radius of curvature 厂ooo0406356 aximum Edge Length Minimum edge length-lower bound on Expansion Factor length scale(default 1% of volume 「12 background scale) Adjust meshing spacings Maximum edge length-upper limit on length scale(default same as volume 厂 Apply Stretch background scale) Volume expansion factor-rate of Proximity Edge expansion of mesh scale from surface to 厂 Surface Interior 710 CFX5.5V5.5.1H 2001AEA Technology

CFX 5.5 V 5.5.1H © 2001AEA Technology 7-10 Surface mesh parameters - Value (degrees) - code chooses edge length such that the set angle is subtended at the centre of circle with radius equal to smallest radius of curvature. Default is 18 degrees (recommended 5 to 60 degrees) - Value (fraction) - deviation of mesh from surface as a fraction of local minimum radius of curvature - Minimum edge length - lower bound on length scale (default 1% of volume background scale) - Maximum edge length - upper limit on length scale (default same as volume background scale) - Volume expansion factor - rate of expansion of mesh scale from surface to interior Curvature Sensitive Mesh

CFX Curvature Sensitive Mesh Examples CFX CFX With surface curvature sensitive Without surface curvature sensitive meshing meshing CFX5.5V5.5.1H 2001AEA Technology

CFX 5.5 V 5.5.1H © 2001AEA Technology 7-11 Without surface curvature sensitive meshing With surface curvature sensitive meshing. Curvature Sensitive Mesh Examples

CFX! Proximity Sensitivity in Surface Mesh Edge proximity is used to automatically modify mesh elements in regions where curved and flat sur faces are in close proximity Bounding curves of surface sense nearby curves and increase mesh tensity locally CFX CFX Without proximity feature With proximity feature CFX5.5V5.5.1H 2001AEA Technology

CFX 5.5 V 5.5.1H © 2001AEA Technology 7-12 Proximity Sensitivity in Surface Mesh Without proximity feature With proximity feature Edge Proximity is used to automatically modify mesh elements in regions where curved and flat surfaces are in close proximity > Bounding curves of surface “sense” nearby curves and increase mesh density locally