Mesh-Intro 14.0 L-05 Global Mesh Controls
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What you will learn from this presentation
Introduction to Global Mesh Settings Description of various settings/inputs
Global Mesh Controls
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Preprocessing Workflow
Sketches andPlanes
Geometry ImportOptions
3D Operations
Direct CAD/Bi-Directional CAD
GeometryCleanup and
Repair
AutomaticCleanup
Merge, Connect,Projection, Flow
VolumeExtraction, etc
Extrude, Revolve,Sweep, etc
3D Operations
Boolean, BodyOperations, Split,
etc
MeshingMethods
Hybrid Mesh: Tet,Prisms, Pyramids
Hexa Dominant,Sweep meshing
Global Mesh
Settings
Local MeshSettings
Sizing,Body/Sphere ofInfluence, Match
Control, etc
Geometry Creation OR
Geometry Import
Geometry Operations Meshing Solver
AssemblyMeshing
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Meshing Process in ANSYS Meshing
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Global Mesh Controls (1) Global mesh controls are used to make
global adjustment in the meshing strategy, which includes sizing functions, inflation, smoothing, defeaturing, parameter inputs, assembly meshing inputs, etc.
Useful to resolve important features of the model with minimal inputs
Automatically calculates global element sizes based on the smallest geometric entity
Smart defaults are chosen based on physics preference For example: Transition ratio,
Transition, Smoothing etc. Makes global adjustments for required
level of mesh refinement Advanced Size Functions for resolving
regions with curvatures and proximity of surfaces
Smart defaults !
Some of the optionsare not available for
Assembly Meshing
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Global Mesh Controls (2)Physics Based Settings Physics and Solver Preferences
Global Mesh Sizing Controls Relevance and Relevance Center Advanced Size Functions Smoothing and Transition Span Angle Center Curvature Normal Angle Proximity Accuracy and Cells Across Gap
Inflation Inflation Option, Inflation Algorithm Collision Avoidance
Maximum Angle, Fillet Ratio, SmoothingAssembly Meshing Activation of CutCell/Tetrahedrons Meshing
Patch Confirming Options Activation of Advancing Front Method
Advanced Shape Checking Element midside nodes
Defeaturing Pinch based Automatic Mesh Based
Statistics Mesh statistics, Quality criteria
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Global Mesh Controls (3)
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Four options under Physics Preference CFD, Mechanical, Explicit and Electromagnetic
Three options under Solver Preference when CFD is selected: Fluent, CFX and POLYFLOW
Mesh setting defaults are automatically adjusted to suit the Physics Preference and Solver Preference
Assembly Meshing is active only when Physics Preference is CFD and Solver Preference is Fluent
Defaults
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Relevance and Relevance Center Useful for automatic Global Refinement or Coarsening of
the mesh
Defaults : Relevance
Coarse Medium Fine
0
100
-100
0100
-100
0100
-100
Relevance Center
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Advanced Sizing Functions (ASF)
Controls the growth and distribution of mesh in important regions of high curvature or close proximity of surfaces
Five Options:
Off. Unavailable for Assembly Meshing
Proximity and Curvature Curvature Proximity Fixed
When CutCellMeshing is active with Proximity or Proximity and Curvature ASF, Proximity Size Function Sources control is displayed to specify the regions of proximity between edges, faces or both in the computation of proximity SF
Sizing : Advanced Sizing Functions
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Sizing : Advanced Sizing Function Examples
ASF: Curvature Determines the Edge and
Face sizes based onCurvature Normal Angle
Finer Curvature Normal Angle creates finer surfacemesh
Transition of cell size isdefined by Growth Rate
ASF: Off The edges are meshed
with global Element Size Then the edges are
refined for curvature and2D proximity
At the end, correspondingface and volume mesh isgenerated
Transition of cell size isdefined by Transition
ASF: Proximity Controls the mesh resolution
on proximity regions in themodel
Fits in specified number ofelements in the narrow gaps
Higher Number of CellsAcross Gap creates morerefined surface mesh
Transition of cell size isdefined by Growth Rate
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Sizing : Advanced Sizing Function Examples
ASF: Proximity & Curvature Combines the effect of
Proximity and Curvaturesize function
More computational time
ASF: Fixed + Local Sizings Mesh is refined locally due to
sizing (on 2 edges for thatexample)
Elsewhere size is defined byMax (Face) Size
Transition of cell size isdefined by Growth Rate
ASF: Fixed Constant mesh size through
out No refinement due to
curvature or proximity in themodel
Surface mesh is generatedwith specified Max FaceSize
Volume mesh is generatedwith specified Max Size
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Sizing : Element SizeElement Size
Element size used for the entire model
This size will be used for meshing all edges, faces and bodies
Default value based on Relevance and Initial Size Seed User can input required value as per geometry dimensions
Element size optionavailable when AdvancedSize Function is not used
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Sizing : Min and Max SizeMin Size
Minimum element size that the size function will generate Some element sizes may be smaller than this size depending on
the edge length
Max Face Size Maximum face size that the size function will generate Not supported by CutCell meshing
Max Size Maximum element size that can be grown in the interior of
volume mesh
Min Size Max Face Size Max Size Max Size
Mouse Pointer serves to estimatemesh sizes
Max Face Size
Min Size
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Sizing : Growth Rate Define the ratio between sizes of adjacent cells
On surfaces and inside the volumes
Mesh size:GR = 1.1 : 1,263,297 cellsGR = 1.2 : 587,026 cellsGR = 1.3 : 392,061 cells
Growth Rate = 1.1 Growth Rate = 1.2 (Default)
Growth Rate = 1.3
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Sizing : Transition Controls the rate at which elements grow
Two level control for transition Slow (Default for CFD, Explicit), produces smooth transitions Fast (Default for Mechanical and Electromagnetic), produces more
abrupt transitions Not available for Cutcell meshing
Hidden for sheet models, ignored for assemblies containing sheets, when ASF is On
Fast Slow
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Sizing : Smoothing Improves quality by moving locations of nodes with respect to
surrounding nodes
Three level control for smoothing iterations High (Default for Explicit)
Medium (Default for Mechanical, Electromagnetic and CFD) Low
For Cutcell meshing, the Smoothing option controls the quality threshold at which it will start smoothing
Low Medium High
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Sizing : Span Angle Center Controls curvature based refinement for Edges
Three options and corresponding span angle ranges are Coarse: 91 to 60 Medium: 75 to 24 Fine: 36 to 12
Not available for Cutcell meshing
Coarse
MediumFine
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Inflation Inflation extrudes faces normal to a boundary to increase the
mesh resolution to: Resolve viscous boundary layer in CFD Resolve thin air gaps in Electromagnetic analysis Resolve high stress concentration regions in Structures
Inflation layers can be generated from tri and quad surface mesh
Can be combined with other meshing methods. Hexa Dominant meshing method can not be inflated
Variety of options to control the growth and quality of inflation layers
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Inflation : Automatic Inflation Three options
None: Select this for manual inflation settings using local mesh controls
Program Controlled: All the faces are selected for inflation
except: Faces scoped to a Named Selection Faces with manual inflation defined Faces in contact regions Faces in symmetry
Faces that belong to a part or body that has a mesh method defined that does not support 3D inflation, such as sweep or hex dominant
Faces in sheet bodies All Faces in chosen Named Selection: can grow inflation
layers from faces grouped in one named selection
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Inflation : Inflation OptionsFive options:
Smooth Transition
Total ThicknessMaintains constant total height of inflationlayer throughout
First Layer ThicknessMaintains constant first cell heightthroughout First Layer
Thickness
Total Thickness
First Aspect Ratio
Last Aspect
Ratio
Smooth TransitionMaintains smooth volumetric growthbetween each adjacent layer. Totalthickness depends on the variation ofbase surface mesh sizes (Default)
First Aspect RatioControls the heights of the inflation layersby defining the aspect ratio of the
inflations that are extruded from theinflation base
Last Aspect RatioCreates inflation layers using the valuesof the first layer height, maximum layers,and aspect ratio controls
All available for PC tets and Assembly meshing
Smooth
Transition
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Inflation : Inflation Algorithms Two Algorithms
Post
Pre
Not available for cutcell meshing
Preview Inflationis available only
with Pre Algorithm
Post
Pre
Surface mesh is inflated first, then rest of the volume mesh grows Default method for Patch Conforming Tetrahedrons
First Tet grows then Inflation process starts Tet mesh is undisturbed, if the inflation options are altered Default option for Patch Independent Tetrahedrons
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Inflation : Advanced OptionsCollision Avoidance: Control to detect proximity regions and adjust the cells in the inflation layer.
None Does not check for proximity regions
Layer Compression (Default for Fluent) Compresses inflation layers in the proximity regions Maintains the given number of layers in the proximity regions May stair step if needed (will give a warning)
Stair Stepping (Default for CFX) Inflation layers are stair stepped in the proximity regions Removing layers locally in steps to avoid collisions as well as bad quality
at sharp corners
When Cutcell meshing
is
used,
both
Layer
Compression
and
Stair
Steeping algorithms are used depending on the geometry complexity.
Generates combinationof Pyramids and Tetsto fill the stair step
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Assembly Meshing: Introduction
Note that when it is activatedsome global and localcontrols are not available
Cartesian/Tetrahedral meshing method acts as a single mesh process for whole model
Patch independent volume meshing approach with automatic edge defeaturing driven by
advanced size functions This is active only when CFD is selected in
Physics Preference and Fluent is selected in Solver Preference
CutCell CutCell results in a cartesian mesh + tets (+ prisms, if
inflation is specified) which is read as polyhedra in Fluent
Tetrahedrons Tetrahedrons results in a tet mesh and also creates
prisms if inflation is specified
To activate Assembly Meshing Set Method to CutCell or Tetrahedrons under
Assembly Meshing option from global controls
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Assembly Meshing: Controls The Feature Capture control determines
which CAD features are captured for assembly meshing
Program Controlled This is the default where a feature angle of 40 degrees is used to determine which features are captured
Feature Angle Exposes an additional Feature Angle field, where you can set a value from 0 to 90 degrees instead of using the default of 40
The Tessellation
Refinement control
specifies
the value to be used for tessellation (faceting) refinement for
Program Controlled This is the default which sets tessellation refinement to 10% of the value of Min Size/Proximity Min Size (whichever is smaller)
Absolute Tolerance Exposes an additional Absolute Tolerance field, where you can set a numerical value for refinement
None Sets tessellation refinement to the CAD program or DesignModeler application default setting
The recommended range for Absolute Tolerance for TessellationRefinement is between 5 and 10% ofthe value of Min Size/Proximity MinSize (whichever is smaller)
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Assembly Meshing: Inflation For the CutCell algorithm, inflation is neither Pre nor Post but may be
considered a hybrid of the two Technology used is like that of the Pre algorithm, but inflation occurs Post mesh
generation
For the Tetrahedrons algorithm, Pre inflation is used, with inflation behaviors very similar to those of the Patch Conforming Tetrahedron mesh method
A mixture of global (automatic Program Controlled) and local (scoped) inflation is not supported
For Virtual Bodies, only automaticProgram Controlled inflation can beused
Only 3D inflation is supported for Assembly Meshing
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Defeaturing Removes small geometry features meeting the tolerances
using Pinch or/and Automatic Mesh Based Defeaturingcontrols in order to improve the mesh quality. Not all meshing methods can take advantage of these controls
Pinch Tolerance control removes small features at the mesh level depending on the Pinch Tolerance value provided. ANSYS Meshing offers global and manual pinch controls
Automatic Mesh Based Defeaturing (AMBD) when it is On, features smaller than or equal to the value of Defeaturing
Tolerance are removed automatically
AMBD Off AMBD On With Pinch
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Statistics Option to view the mesh quality metric Exhaustive list of quality metrics Orthogonal Quality mesh quality metrics Option to view the Mesh Metric chart
Intuitive controls
available
under
Mesh
Metric
Chart
Various options to explore under the Controls
See lecture 5 for details
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Workshop 3 Global Mesh Controls
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Contents Sizing: ASF Controls Sizing: Initial Size Seed Sizing: ASF Examples Sizing: CutCell Inflation: Advanced Options Advanced Controls
Appendix
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Sizing : ASF Controls (Curvature & Proximity)Curvature Normal Angle Defines the maximum angle between face normals
Smaller angles will produce smaller cells on curved faces capturing geometric curvature more accurately
Num Cells Across Gap Minimum number of cells spanning gaps Required to resolve flow gradients
Proximity Accuracy Range 01 0 faster, less accurate & 1 slower, more accurate
Default value of 0.5 is a good compromise
Geometry
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Sizing : Initial Size Seed Controls how the initial sizes are assigned
Three options: Active Assembly:
Assigned based on the diagonal of the bounding box of unsuppressed parts
Mesh can change with varying bounding box sizes for various suppressed/unsuppressed parts
Full Assembly: Assigned based on the diagonal of the bounding box of
all assembly parts regardless of the number of
suppressed parts Mesh never changes if parts are
suppressed/unsuppressed
Part: This option is not available when ASF is On Assigned based on the diagonal of the bounding box of
each particular individual part as it is meshed The mesh never changes due to part suppression Typically generates finer mesh
Not available for Assembly (CutCell/Tetrahedrons) Meshing
Suppressed body
Unsuppressed body
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Sizing : Advanced Sizing Functions
ASF : Off The edges are meshed
with global element sizecomputed by the mesher
Then the edges arerefined for curvature and
2D proximity At the end, corresponding
face and volume mesh isgenerated
ASF : Curvature Determines the Edge and
Face sizes based onCurvature Normal Angle
Curvature Normal Angleis the max angle b/w
adjacent Face normals Finer Curvature Normal
Angle creates finer surfacemesh
Fluid gap
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Sizing : Advanced Sizing Functions
ASF : Proximity & Curvature Combines the effect of
Proximity and Curvature size function
More computational timedue to combined effect ofCurvature and Proximity
ASF : Fixed Constant mesh size through out No refinement due to
curvature or
proximity
in
the
model
Surface mesh is generated with specified Max Face Size
Volume mesh is generated with specified Max Size
ASF : Proximity Controls the mesh resolution
on proximity regions in the model
Fits in specified number of elements in the narrow gaps
Higher Number of Cells Across Gap creates more refined surface mesh
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Sizing : Advanced Sizing Functions with CutcellFixed
Proximity
Curvature
Proximity and Curvature
Cutcell meshes generated with default settings
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Inflation : Advanced OptionsGap Factor Controls the size of Tet element to be filled in the gap after
inflation layers are generated
For Gap Factor of 1, gap is controlled such that a tetra element with height matching the base element size can fit in the gap
Applicable only when the Collision Avoidance is Layer Compression or Stair stepping
Gap Factor = 0.5 (Default) Gap Factor = 1
Higher Gap Factor meansmore layer compression
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Inflation : Advanced OptionsFix First Layer Control for fixing the first layer height throughout
the model
Growth Rate Type Three types available
Exponential, Geometric, Linear Controls the inflation layer height with selected
growth rate type
No Yes
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Inflation : Advanced OptionsGrowth Rate Type
Exponential
Geometric (Default)
Linear
)1(1
nn r hh
r
r h H
n
n
1
)1(1
pnn ehh )1(1
)]1)(1(1[1 r nhhn
22)1)(1(
1r n
nh H nWhere h1 is the initial layer height,hn is the height of layer n, r is thegrowth rate, p an exponent, andH n is the total height at layer n
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Inflation : Advanced OptionsMaximum Angle Controls the projection/imprinting of the inflation
layers on the adjacent faces
Maximum Angle = 140 Maximum Angle = 180
Adjacent Face Angle = 160
Higher Maximum Angle means more chancesof layer projection on adjacent faces
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Inflation : Advanced OptionsFillet Ratio Generates the inflation layers at corner with fillet
like smoothing, proportional to inflation height Controls smoothing of corner nodes of inflation
layers for better quality
Fillet Ratio = 1Fillet Ratio = 0
Higher Fillet Ratio means moresmoothing for corner nodes
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Inflation : Advanced OptionsMaximum Height over Base Controls the allowable ratio of last inflation layer
height over the base element size Once this allowable value is reached, inflation
layers are grown but the cell height remainsconstant Valid values are from 0.1 to 5. The default is 1.0
Max Height over Base = 0.1Max Height over Base = 1
Higher Max Height overBase means thickerinflation height
The value has been reached,the prism growing continueswith constant height
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Advanced Controls Advanced group is not accessible for Cutcell meshingShape Checking The quality criterion varies with the type of physics
For CFD uses a shape checking criterion based on the element
volume for any Non Cutcell meshing, and on the orthogonal quality for Cutcell meshing
Mesh check fails if the above criteria is not metElement Midsize Nodes Control for creating element with (quadratic element) or
without (linear element) midsize node Higher order solution for Mechanical Analysis
Not required for CFD Default option Dropped
See the Users Guide for more details
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