Mesh_Intro_FEA_2021R1_EN_LE03.pdf

©2021 Ansys, Inc. Unauthorized use, distribution, or duplication is prohibited.
Introduction to Ansys Meshing for FEA
Release 2021 R1
Module 03: Global Mesh Controls

Learning Outcomes
After completing this module, you will be able to:
• Get a good idea about the different global mesh controls
• Know what are the default settings in the details of Mesh
• Set the General Sizing Controls & Advanced Size Functions
• Understand what global defeaturing is used for
2

Agenda
• Global Mesh Controls
• Defaults
• General Sizing Controls & Advanced Size Functions
• Global Defeaturing
3

Geometry
Import /
Creation
Geometry
Cleanup /
Modifications
Meshing
Preprocessing
and Solution
Preprocessing Workflow
4

Core
Skills
Global
Controls
Local
Controls
Mesh
Quality
Meshing
Methods
Module 1
Module 2
Module 3
Module 4
Module 5
Mesh Process & Course Plan
5

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…
• Minimal inputs
‐ Automatically calculates global element sizes
based on the smallest geometric entity
‐ Smart defaults are chosen based on physics
preference
• Makes global adjustments for required
level of mesh refinement
• Advanced Size Functions for resolving
regions with curvatures and proximity
of surfaces
6

Global Mesh Controls (2) • Display
‐ Change Mesh color by quality metrics
• Defaults
‐ Physics and Solver Preferences
‐ Element midside nodes
‐ Element size
• Global Mesh Sizing Controls
• Adaptive Sizing
• Span angle center
• Transition
• Curvature Normal Angle
• Mesh Defeaturing
• Quality
• Check Mesh Quality
• Smoothing
• Quality Metrics
• Inflation (mostly used for CFD)
‐ Inflation Option, Inflation Algorithm
‐ Collision Avoidance
‐ Maximum Angle, Fillet Ratio, Smoothing
• Advanced
‐ Numer of CPUs for Parallel Part Meshing
‐ Shape Checking
‐ Mesh strategy for patch conforming mesher
‐ Validation of the patch independent topology
‐ Pinch based Defeaturing
• Statistics
‐ Mesh statistics
7

Quick Workshop 03.1
Open the archive ‘Quick_Workshop_03.1’
• Check the geometry and the mesh default Physics Preference
• Generate the mesh without changing anything
• Change the Physics Preference to Nonlinear Mechanical and generate the mesh again
• Compare the two meshes and note how this only global control has changed the mesh
8

Defaults • Six options under “Physics Preference”
– Mechanical, Nonlinear Mechanical, Electromagnetics, CFD, Explicit and Hydrodynamics
• Mesh setting defaults are automatically adjusted to suit the
“Physics Preference” and “Solver Preference”
• The Nonlinear Mechanical
Physics Preference may result
in higher mesh quality for FEA
users.
• Hydrodynamics has been
added to improve meshing
capability for Hydrodynamics
Diffraction (AQWA)
9

Sizing: Size Function
• Controls the growth and distribution of
mesh in important regions of high
curvature or close proximity of surfaces
• Adaptive size function is not
recommended because it requires
transition and Span Angle Center
• Best practice is to use Nonlinear
Mechanical in physics preference
10

SF: Curvature
• Determines the Edge and Face sizes
based on Curvature Normal Angle
• Finer Curvature Normal Angle creates
finer surface mesh
• Transition of cell size is defined by
Growth Rate
SF: 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
• Transition of cell size is defined by Growth
Rate
Sizing: Sizing Function Examples
11

Sizing: Min and Max Size
(only available when the size function is not set to Adaptive)
• Min Size
– Minimum element size that the size function will generate
– Some element sizes may be smaller than this size depending on the edge
length
• Element Size
– Maximum face size that the size function will generate
• 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 estimate
mesh sizes
Max Face Size
Min Size
12

Sizing: Growth Rate
(only available when the size function is not set to Adaptive)
• Define the ratio between sizes of adjacent cells
- On surfaces and inside the volumes
Mesh size:
GR = 1.1 : 1,263,297 cells
GR = 1.2 : 587,026 cells
GR = 1.3 : 392,061 cells
Growth Rate = 1.1 Growth Rate = 1.2 (Default)
Growth Rate = 1.3
13

Sizing: Transition
(only available when Use Adaptive Sizing is set to Yes)
• Controls the rate at which elements
grow
• Two level control for transition
• Slow: produces smooth transitions
• Fast: produces more abrupt transitions
• Hidden for sheet models, ignored for
assemblies containing sheets, when SF is
not set to adaptive
Fast Slow
14

Defeaturing • Removes small geometry features meeting the tolerances using
Pinch or/and Automatic Mesh Based Defeaturing controls in order
to improve the mesh quality.
• Automatic Mesh Based Defeaturing (AMBD) when it is ‘On’,
features smaller than or equal to the value of Defeaturing
Tolerance are removed automatically.
Note: Defeaturing Tolerance can be set maximum up to Global Min Size/2. Use a high value
for Global Min Size and use Local Sizing controls for defining Local Min Sizes smaller than
this value. Defeaturing will respect local min sizes and will clean only those faces/bodies
with no local control. This approach is recommended over Virtual Topology
AMBD Off AMBD On
15

Summary
• The main global controls are: Physics Preference, sizing functions, inflation, smoothing,
and defeaturing. Those controls affect the mesh on the entire model
• By default, the physics preference is set to Mechanical, one should change it to CFD to
get a mesh suited for CFD applications with ‘Capture Curvature’ set to on
• Defeaturing will remove features smaller than or equal to the value of Defeaturing
Tolerance in order to improve the mesh quality
16

Workshop 3.1 FEA – Global Mesh Controls
17

Inflation
• Used to generate thin cells adjacent to
boundaries
• Required for capture of wall adjacent
boundary layers
‐ Resolve thin air gaps in Electromagnetic
analysis
‐ Resolve high stress concentration regions in
Structures
• Cells are created by ‘inflating’ from the
surface mesh into the volume (3d) or
inflating from the boundary edge onto
the face (2d)
• Options to control growth
19

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 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
• Faces scoped to a Named Selection if the ‘Program
Controlled Inflation’ is kept to the default option
‘Exclude’ in the details of the named selection. If you
change this option to Include, the named selection
will not be excluded
‐ All Faces in chosen Named Selection:
• can grow inflation layers from faces grouped in one
named selection
20

Mesh_Intro_FEA_2021R1_EN_LE03.pdf

Recommended

Recommended

More Related Content

Similar to Mesh_Intro_FEA_2021R1_EN_LE03.pdf

Similar to Mesh_Intro_FEA_2021R1_EN_LE03.pdf (20)

Recently uploaded

Recently uploaded (20)

Mesh_Intro_FEA_2021R1_EN_LE03.pdf