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Module 01: Core Skills Introduction to ANSYS Meshing Dr. Ahmed Nagib Elmekawy

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Page 1: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Module 01: Core Skills

Introduction to ANSYS Meshing

Dr. Ahmed Nagib Elmekawy

Page 2: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

In this lecture we will learn:

• Meshing Fundamentals

• ANSYS Meshing interface

• Geometry concepts

• Meshing methods

• Diagnostics & Usability

• Display Option

• Mesh Statistics & Mesh Metrics

2

Overview

Page 3: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Preprocessing Workflow

Geometry Import / Creation

Geometry Cleanup / Modifications

MeshingPreprocessingand Solution

3

Page 4: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Mesh Process & Course Plan

4

CoreSkills

Module 1

MeshingMethods

Module 2

GlobalControls

Module 3

LocalControls

Module 4

Mesh Quality

Module 5

Page 5: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

ANSYS Meshing is a component of ANSYS Workbench

• Meshing platform

• Combines and builds on strengths of preprocessing offerings from ANSYS:

– ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh, Gambit

Able to adapt and create Meshes for different Physics and Solvers

• CFD: Fluent, CFX and POLYFLOW

• Mechanical: Explicit dynamics, Implicit

• Electromagnetic

Integrates directly with other WB systems

5

What is ANSYS Meshing

Page 6: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Purpose of the Mesh

• Equations are solved at cell/nodal locations–Domain is required to be divided into

discrete cells (meshed)

Mesh Requirements

• Efficiency & Accuracy

– Refine (smaller cells) for high solution gradients and fine geometric detail.

– Coarse mesh (larger cells) elsewhere.

• Quality

– Solution accuracy & stability deteriorates as mesh cells deviate from ideal shape

Meshing Fundamentals

6

Page 7: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Fluid Flow (Fluent), Static Structural,…

ANSYS Meshing is launched within Workbench

– 2 ways:

From Analysis SystemsMesh

From Component Systems

Double click Mesh in the

System

or right click and select Edit

Launching ANSYS Meshing

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Page 8: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Mesh Metrics

Graphics window

Section Planes

Manage views

Details view

Outline

Toolbars

Units BarEntity Details Bar

Message window

Worksheet

Graphical User Interface

8

Page 9: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Three default sections

• Geometry

– Bodies

• Coordinate Systems– Default global & user defined systems

• Mesh

– Meshing operations (controls & methods)

▪ displayed in the order in which they are inserted

In the tree

• Right clicking on any object– launches a context sensitive menu

– Example: contains commands to generate, preview, clear mesh etc.

Outline

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Page 10: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Accessing Object Details

• Select an object (in the Outline)

– Related information to that object are displayed in the Details View below

– Ex: Select a body (“Fluid”) in the Outline

• Details of “Fluid” : contains graphical and geometric details

– To access meshing details

• Click the Mesh object or any of the inserted objects

• The Details View provides options to– review,

– edit, or

– input

values for every object in the Tree

Details View

10

Page 11: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

• Geometry composed of Multiple parts

– No connection between parts (no face sharing)

‘Contact Region’ is automaticallycreated between2 faces

Each part meshed independently

Results in Non-conformal interface.Meshes do not match.

No nodes connection.

Independent faces

Grid interface- Fluent

GGI - CFX

Geometry Configuration – Multiple Parts

Contact -Mechanical

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Page 12: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

• Hexa: Concentration in one direction– Angles unchanged

• Tetra: Concentration in one direction– Angles change

• Prism: Concentration in one direction– Angles unchanged

Hexa vs. Tetra

Hexa

Tetra

Prism

Tetra (in volume)

Prisms (near wall)

12

Page 13: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

• Geometry composed of multiple bodies in a part

– Depend on ‘Shared Topology method’ (in DM)

• None

– Results in a no connection between the bodies (similar tomultiple parts)

• Automatic

Common face acts as ‘Interior’

Note: The CFX users will still get duplicate nodes at interface in CFX, which is fine for its solver

Geometry Configuration – Multi-bodyParts

Faces in contact imprinted & fused toform a single face shared between 2 bodies

Results inConformal mesh

13

Page 14: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

• Geometry composed of multiple bodies in a part

• Imprints

Faces are imprinted on each other ➔ ‘like’ faces

Contact Regionis automaticallycreated

non conformal interface

For identical mesh on these faces, use ‘Match Control’ Results in unconnected mesh

Grid interface- Fluent

GGI - CFX

Geometry Configuration – Multiple – body Parts

14

Page 15: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Part/Body based• Meshing occurs at part or

body level.• Meshing Methods are scoped

to individual bodies.

• Method assignment can be automatic or manual.

• Bodies contained in one partare conformally meshed.

• 3D cell Types

• First Meshing Approach

Part/Body Methods

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• Tetrahedrons.− Tetras only

• Sweep.− Prisms & hexahedrons

• MultiZone.− Mainly hexahedron

• Hex Dominant− Not for CFD

• Automatic.− Sweep + PC Tet (Depends

on bodies) or PC Tet

Meshing – 3D Geometry (1)

Page 16: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

• Second Meshing Approach (mainly for CFD users)

Cut Cell MeshingAssembly Meshing• Meshes an entire model in one

process.− Assembly of parts

• Performs boolean operations.− Volume filling, intersection &

combination

− Does not require prior fluid bodydefinition or shared topology.

• Conformal mesh created across parts.

Assembly MeshingMethods• Generate mainly

− Hexahedrons− Tetrahedrons

Part/Body Meshing & Assembly Meshing

not interoperable

16

Meshing – 3D Geometry (2)

Page 17: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Default meshdisplay

Turning wireframe mode on

Turning on Mesh display bybodyconnection.

Diagnostics: Mesh display By Body Connection (New in R17.0)

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Page 18: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Named Selections are groups of geometric or finite element entities:

• Named selections can be created either by selecting the desired items and clicking the “NamedSelection” icon in the context toolbar or RMB > Named Selection OR using the named selectionworksheet (shown later).

• Named selections must be composed of “like” entities (all surfaces or all edges, all nodes, etc.).

RMB

Named Selections (1)

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Page 19: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

A new criteria selection can be based on an initial selection:

• Make an initial selection followed by a RMB > “Create Named Selection”.

• Note, initial selection must be a single entity.

RMB >

Selection here will create the first row of the worksheet.

Convert to nodal named selection immediately.

Named Selections (2)

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Page 20: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

In many detail window fields Named Selections can be referenced directly:− In the Details view, change “Scoping Method” from “Geometry Selection” to “Named

Selection”− Select the “Named Selection” from the pull-down menu

− A named selection toolbar provides quick access to basic controls “View > Toolbars > Named Selections”:

Named Selections (3)

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Page 21: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Usability: Option to save mesh out to separate file (New in R17.0)

● When “Save Mesh Data in Separate File” is on the mesh is saved as a separate file (*.acmo).

● Duplication, Resume, Replace, and Save will handle the separate database and acmo files.

● Clear generated data will not remove the acmo file. Reset will remove the acmo file.

● Design Points (also w/RSM) support the separate database and acmo files.

This functionality is particularly helpful on Linuxto keep file sizes smaller.

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Page 22: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Usability: Better Meshing Status in R17.0

● Progress is reported as parts are meshed in parallel● As a part is meshed the topology (edges, faces, bodies) are highlighted to show what is

being worked on– This can be turned off by unchecking “Highlight”– If user stops meshing, entity will stay highlighted, allowing user to find problematic geometry easier

If user stops meshing, parts that have been meshed are done. Restarting meshing resumes only with unmeshed parts

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Page 23: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

● Mesh controls can now be grouped for easierorganization

● Option: Group All Similar Children, will group all objects based on type

● Options to suppress, rename, nest groups, ungroup, delete objects in group

● Drag and drop capabilities to modify the grouping

Usability: Folders for Meshing Controls in R17.0

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Page 24: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

• Displays mesh color by quality metrics

• Options to probe quality or show min/max

• Contour band can be adjusted

Display meshcontours

Find Min orMax value

Probe ElementValues

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Display Option: Color by quality

Page 25: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Displays internal elements of the mesh

• Elements on either side of plane can be displayed

• Toggle between cut or whole elements display

• Elements on the plane

Edit Section Plane button can be used to drag section plane to new location• Clicking on “Edit Section Plane” button will make section plane’s anchor to appear

Multiple section planes are allowed

For large meshes, it is advisable to switch to

geometry mode (click on geometry in the Tree

Outline), create the section plane and then go

back to mesh model

Section Planes (1)

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Page 26: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Section Planes (2)

● Shaded section planes (New in R17.0)

– Shaded or hollow section plane

– Plot by body color or same color for section plane

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Page 27: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

• Displays mesh information for Nodes and Elements

• List of quality criteria for the Mesh Metric

– Different physics and different solvers have different requirements for mesh quality

Mesh metrics available in Workbench Meshing include:

– Element Quality– Aspect Ratio– Jacobean Ration– Warping Factor– Parallel Deviation– Maximum Corner Angle– Skewness– Orthogonal Quality

For Multi-Body Parts, go to corresponding body in TreeOutline

to get its separate mesh statistics per part/body

Mesh Statistics & Mesh Metrics

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Page 28: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

• Displays Mesh Metrics graph for the element quality distribution

• Different element types are plotted withdifferent color bars

• Can be accessed through menu bar using Metric Graph button

• Axis range can be adjusted using controls button (details next slide)

• Click on bars to view corresponding elements in the graphics window– Use to help locate poor quality elements

Mesh Metric Graph

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Page 29: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Mesh Metric Graph Controls

• Elements on Y-Axis can be plotted with two methods;– Number of Elements

– Percentage of Volume/Area

• Options to change the range on either axis

• Specify which element types to include in graph

– Tet4 = 4 Node Linear Tetrahedron

– Hex8 = 8 Node Linear Hexahedron

– Wed6 = 6 Node Linear Wedge (Prism)

– Pyr5 = 5 Node Linear Pyramid

– Quad4 = 4 Node Linear Quadrilateral

– Tri3 = 3 Node Linear Triangle

• Te10, Hex20, Wed15, Pyr13, Quad8 & Tri6 non-linear elements

For more information about the different mesh metrics please consult module 05: MeshQuality

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Page 30: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

What have we learnt in this session:

• The global process to run ANSYS Meshing

• On overview of the interface and

• The various Geometry configurations

– Multipleparts

– Multi-body parts

– Multiple body parts

• Meshing methods– Part/body based

– Assembly meshing

• Section Planes

• Diagnostics & Usability

• Mesh Statistics & Mesh Metrics

• Display option

And the associated

shared topology option

Summary

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Page 31: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Workshop 1.1 CFD – ANSYS WB Meshing Basics

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Page 32: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Workshop 1.1 FEA – ANSYS WB Meshing Basics

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Page 33: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Module 2: Meshing Methods

Introduction to ANSYS Meshing

Page 34: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Meshing Methods

34

What you will learn from this presentation

• Meshing Methods for Part/Body Meshing

– Assembly Meshing covered separately

• Methods & Algorithms for;

– Tetrahedral Meshing

– Hex Meshing

– 2D Meshing

• Meshing Multiple Bodies

– Selective Meshing

– Recording Meshing Order

Page 35: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Preprocessing Workflow

Sketches and

Planes

Geometry Import

Options

3D Operations

Direct CAD/Bi-

DirectionalCAD

Geometry

Cleanup and

Repair

Automatic

Cleanup

Merge, Connect,

Projection, Flow

Volume

Extraction, etc

Extrude, Revolve,

Sweep, etc

3D Operations

Boolean, Body

Operations,Split,

etc

Meshing

Methods

Hybrid Mesh: Tet,

Prisms, Pyramids

Hexa Dominant,

Sweep meshing

Global Mesh

Settings

Local Mesh

Settings

Sizing,

Body/Sphere of

Influence,Match

Control,etc

Geometry Creation OR

Geometry Import

Geometry Operations

Meshing Solver

Assembly

Meshing

35

Page 36: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Why Multiple Methods?

• Choice can depend on;

– Physics

– Geometry

– Resources

• Mesh could require just one or a combination of methods.

• Example – Typical mesh design based on geometric, physicsand resource considerations.

Methods

High aspect ratio cells (Inflation) near wall to capture boundary layer

gradients

Tet (3d) or Tri (2d) cells used here to mesh complex region

Hex (3d) or Quad (2d) cells used to

mesh simple regions

Cells refined around small geometric

details and complex flow

36

Page 37: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

• In the Outline, right click Mesh, Insert > Method

– Select body in Details View

• Or, in the Graphics Window, Select body(s) , right click, Insert > Method

– Body automatically selected in Details View

• Method is selectable using the drop downbox

– Select, Automatic, Tetrahedrons, Hex Dominant,Sweep or Multizone

Inserting Methods

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Page 38: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Method Behavior

• Generates tetrahedral elements - two algorithms are available:

• Patch Conforming

• Patch Independent

38

Tetrahedrons Method

Page 39: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Method & Algorithm Behavior

• Bottom up approach: Meshing processstarts from edges, faces and then volume

• All faces and their boundaries are respected (conformed to) and meshed

• Good for high quality (clean) CAD geometries

– CAD cleanup required for dirty geometry

• Sizing is defined by global and/or local controls

• Compatible with inflation

Access

• Insert Method and set to Tetrahedrons

– Additional drop down box for algorithm choiceappears - Set to Patch Conforming

Tetrahedrons Method: Patch Conforming

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Page 40: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Method & Algorithm Behavior

• Top down approach: Volume mesh generated first and projected on to faces and edges

• Faces, edges and vertices not necessarily conformed to

– Controlled by tolerance and scoping of Named Selection, load or other object

• Good for gross de-featuring of poor quality (dirty) CAD geometries

• Method Details contain sizingcontrols

• Compatible with inflation

Access

• Insert Method and set to Tetrahedrons

– Additional drop down box for algorithm choice appears - Set Patch Independent

Tetrahedrons Method: Patch Independent

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Page 41: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Tetrahedrons Method: AlgorithmComparison (Surface Mesh)

Geometry containing

small details

Patch Conforming:All

geometric detail is

captured

Patch Independent: Can

ignore and defeature

geometry

Page 42: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Tetrahedrons Method: AlgorithmComparison (Volume Mesh)

Geometry containing

small details

Patch Conforming:

Delaunay mesh –

smooth growth rate

42

Patch Independent: Default

Octree Mesh – approximate

growth rate

Smooth Transitionoption

creates Delaunay mesh

Page 43: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Patch Conforming

• Sizing

– Mesh sizing for the Patch Conforming algorithm is defined by Global & Local Controls

– Automatic refinement based on curvature and/or proximity accessible in Global Controls

• Details of Global & Local Controls covered in separate lectures

– Choice of surface mesher algorithm in global controls

Tetrahedrons Method: Control

Proximity

Curvature

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Page 44: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Patch Independent

• Sizing

– Sizing for the Patch Independent algorithm defined in Patch Independent Details

– Automatic curvature & proximity refinement option

Tetrahedrons Method: Control

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Page 45: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Patch Independent

• Defeaturing Control

– Set Mesh Based Defeaturing On

– Set Defeaturing Tolerance

– Assign Named Selections to selectively preserve geometry

Tetrahedrons Method: Control

Defeaturing Tolerance Off

Named Selection assigned and Defeaturing Tolerance= 0.03m. Features > 0.03m respected.

45

Page 46: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Patch Conforming

• Clean CAD, accurate surface mesh

Patch Independent

• Dirty CAD, defeatured surface mesh

Tetrahedrons Method: ApplicationExamples

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Page 47: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Hex Meshing

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Page 48: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Hex Meshing

• Reduced element count

– Reduced run time

• Elements aligned in direction of flow

– Reduced numerical error

Methods Available

• Sweep

• MultiZone

• Hex Dominant (not recommended for CFD)

Initial Requirements

• Clean geometry

• May require geometric decomposition

Introduction

Tet Mesh

Elements: 48K

Sweep Mesh

Elements: 19K

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Page 49: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Method Behavior

• Meshes source surface, sweeps through to the target

– Body must have topologically identical faceson two ends, (which act as source and targetfaces)

• Generates hex/wedge elements

• Side faces must be mappable

• Only one source and one target face is allowed

– Alternative ‘Thin’ sweep algorithm can have multiple source and target faces

Access

• Insert Method and set to Sweep

Sweep Meshing

Source FaceTarget Face

Side Face(s)

Sweep Path

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Page 50: Introduction to ANSYS Meshing Module 01: Core Skillsdrahmednagib.com/CAD_2018/Lecture_2_Meshing_1.pdf · –ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh,Gambit Able to adapt and create

Source/Target (Src/Trg Selection)

• Automatic

– Source & target faces identified automatically

– Not compatible with inflation

• Manual Source & Manual Source and Target

– User selection (required for inflation)

– Compatible with inflation

• Automatic Thin & Manual Thin

– Multiple source and target faces

– Not compatible

with inflation

Sweep Meshing

Sweep Direction Source Face Target Face

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• Inflation

– Must specify at least Source manually when using Inflation & Sweep Method

– 2D inflation defined on source face from boundary edges then swept through volume, source must therefore be specified first

Sweep Meshing

Src/Trg Selection Behaviour

• Automatic selection requires that the application find the Source and Target. Specifying both Source & Target will accelerate meshing

Sweep Mesh No inflation

Automatic Selection

Sweep Mesh with inflation

Manual Selection

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Rotational Sweeping

• Sweep meshes can also be created by sweeping a Source around an axis

• Example: Src/Trg Selection -Rotational sweep for sectorgeometry

– Rotational sweeping requires both Source & Target to be selected

• For both rotational and axial sweeping Source & Target faces are color coded when selected

Sweep Meshing

Manual Source &

Target Selection

Target

Face

Source

Face

Sweep Path

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Target

Src/Trg Selection: Automatic Thin & Manual Thin

• Selects an alternate sweep algorithm

• Advantages

– Capable of sweeping multiple Source & Targets

– Can perform some automatic defeaturing

• Disadvantages

– For Multibody Parts only one division across the sweep is allowed

– Inflation & Sweep Bias notallowed

Sweep Meshing

Source

Faces

Source Faces

Imprinted on Target

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Sweep Meshing

How to Identify Sweepable bodies

• ANSYS Meshing can identify sweepable bodies automatically

– Rotational Sweep bodies are not identified

• Right click Mesh object in Outline and select Show > Sweepable Bodies

RMB on Mesh to find

sweepable bodiesGeometry Sweepable bodies in

green color

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Sweep Meshing

How to Ensure Bodies are Sweepable

• Bodies which will not allow sweeping can be decomposed into anumber of topologically simpler sweepable bodies

• Decomposition can be performed in CAD/DM

• Example 1

Unsweepable body

55

Decomposed in

CAD/DM

Sweepable!

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Example 2

Sweep Meshing

T Junction Geometry

Unsweepable

Decomposed in

CAD/DM

Sweepable!

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Method Behavior

• Based on blocking approach used in ANSYS ICEM CFD Hexa

• Automatically decomposes geometry into blocks

• Generates structured hex mesh where block topology permits

– Remaining region (Free Mesh) filled withunstructured Hexa Core or Tetra or HexaDominant mesh.

• Can select source & target faces automatically or manually

– Can have multiple source faces

• Compatible with 3D inflation

MultiZone Meshing

MultiZone

Mesh

Access

• Insert Method and set to Multizone

Target faces should also be selected as “Source” for Multizone Method as mesh is swept from both directions

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Release 14.5

• Mapped Mesh Type - determines the shape of the elements used to fill structured regions (the default is Hexa).

• Hexa - All hexahedral elements are generated

• Hexa/Prism - For swept regions, the surface mesh canallow triangles for quality and transitioning

• Prism - All prism elements are generated

– This option is sometimes useful if the source facemesh is being shared with a tet mesh, as pyramids are not required to transition to the tet mesh

• Surface Mesh Method – specifies method to create thesurface mesh.

• Program Controlled - automatically uses a combination of Uniform and Pave mesh methods depending on the mesh sizes set and face properties

• Uniform - uses a recursive loop-splitting method which creates a highly uniform mesh

• Pave - creates a good quality mesh on faces with high curvature, and also when neighboring edges have a high aspect ratio

MultiZone Meshing

Surface mesh method = Uniform

Surface mesh method = Pave

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Example 1

• Single body automatically decomposed into three blocks

• Src/Trg Selection – Automatic

• Results in all hex mesh

• Equivalent to manually decomposing by slicing off upper and lower cylinders to produce three bodies and applying sweep methods

MultiZone Meshing

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Example 2

• Blend on central body, Multizone no longer ableto create structured block

– Filled according to Free Mesh setting

• Tetra, Hexa Core, Hexa Dominant

• Can specify type of surface mesh using Mapped Mesh Type (Hexa, Hexa/Prism, Prism)

MultiZone Meshing

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Automatic Method

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Method Behavior

• Combination of Tetrahedron Patch Conforming and Sweep Method

– Automatically identifies sweepable bodies and creates sweep mesh

– All non-sweepable bodies meshed using tetrahedron Patch Conformal method

• Compatible with inflation

Access

• Default Method where not specified

• Can specify by inserting Method andsetting to Automatic

Automatic Method

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2D Meshing

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• Patch Conforming Methods

– Automatic Method (Quadrilateral Dominant) & Triangles

• Patch Independent Methods

– Multizone Quad/Tri

– Full Quad will be generated if "All Quad" is selected as Free Face Mesh Type

• Advanced size functions and local size controls are supported

Methods for 2D Meshing

Automatic Triangles

Multizone

Quad

Multizone

Quad/Tri

Multizone Quad/Tri & Multizone Quad Methodswere previously called Uniform Quad/Tri and Uniform Quad till R14.0

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Mapped Surface Meshes

• Fully mapped surface meshes and specified edge sizing/intervals can be obtained by applying local controls

– Covered in the Local Mesh Controls lecture

2D mesh with Inflation

• Boundary edges are inflated

• Support for global and local inflationcontrols

2D Meshing Control & Inflation

2D

Mapped

Mesh

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ANSYS FLUENT

• For a 2D analysis in FLUENT generate the mesh in the XY plane (z=0).

• For axisymmetric applications y 0 and make sure that the domain is axisymmetric about x axis

• In ANSYS Meshing, by default, a thickness is defined for a surface body and is visible when the viewis not normal to the XY Plane. This is purely graphical – no thickness will be present when the mesh is exported into the FLUENT 2D solver

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ANSYS CFX

• For 2D analysis in CFX, create a volume mesh (using Sweep) that is 1element thick in the symmetry direction, i.e.,

• Thin Block for Planar 2D

• Thin Wedge (< 5°) for 2D Axis-symmetric

2D Mesh Solver Guidelines

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Meshing Multiple Bodies

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Selective Meshing

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What is Selective Meshing?

• Selectively picking bodies and meshing them incrementally

Why use Selective Meshing?

• Bodies can be meshed individually

• Mesh seeding from meshed bodies influences neighboring bodies (user has control)

• Automated meshing can be used at any time to mesh all remaining bodies

• When controls are added, only affected body meshes require remeshing

• Selective body updating

• Extensive mesh method interoperability

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Local meshing

• Mesh or clear meshes on individualbodies

• Subsequent bodies will use the attachedface mesh

• The meshing results (cell types) will depend on the meshing order

• Adjust/add controls – able to remesh only affected body

• Select body(s) right click for context menu

Selective Meshing

Meshing first the block then thepipeMeshing first the pipe then theblock

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Recording Mesh Operations

• When using selective meshing the order of meshing can be recorded for automated future use

• Right click Mesh in the Outline for Context Menu

• Worksheet is generated recording mesh operations as ordered steps

• Named Selections are automatically created for each meshed body for reference in the Worksheet

– Example; Meshing cylinder then block

Selective Meshing

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Selective Body Updating

• Remeshing only bodies that have changed

• Access option through Tools > Options

– No: All geometry updated, all bodies remeshed.

– Associatively: Accommodates for body topology change (add/delete) (slower)

– Non-Associatively: Assumes no topologychange (faster)

• Example; Geometric change to block.

Selective Meshing

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Workshop 2 – Introducing Meshing Methods

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Appendix

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Contents

• Hex Dominant Meshing

• Sweep Meshing Biasing & Complex Geometry

• Surface Meshing with Inflation

• Mesh Connections

• Shell Meshing

• Patch Independent Tetrahedrons - Transition

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Hex Dominant Meshing

• The mesh contains a combination of tet and pyramid cells with majority of cell being of hex type

• Useful for bodies which cannot be swept

• Useful for CFD applications not requiringinflation

• Useful for CFD in the range of acceptable Skewness or Orthogonal Quality mesh quality metrics

Access

• RMB on Mesh

• Insert →Method

• Definition →Method

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Hex Dominant Meshing

• Example:

Geometry with

valve inside

Hex Dominant

Mesh generated

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Hex Dominant Meshing

Free (unstructured) Face Mesh Types

• Determines the element shape in the free zone (wherestructured meshing is not possible)

Options

• Quad/Tri

• All Quad

– May insert triangular elements depending on complexity of geometry

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Hex Dominant Meshing

Example:

Geometry with

valve inside

Free Face Mesh Type:

Quad/Tri

Free Face Mesh Type:

All Quad

Higher no. of

elements

Lower no. of

elements

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Sweep Meshing

• Control:

• Free (unstructured) Mesh Type

Sweepable Geometry

Source face

elements: Only

Quad

Source face

elements: Quad

plus Tri

Source face

elements: OnlyTri

Type: All Quad

Type: Quad/Tri

Type: AllTri

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Sweep Meshing

Control: Type

Element size in

swept direction

2mm

No. of elements in

swept direction: 10

Sweep Element Size

Sweep Num Divisions

Sweepable Geometry

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Sweep Meshing

• Control: Sweep Bias Type

Uniform mesh

Cells are

concentrated on

one side

No Bias

With Bias

Sweepable Geometry

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Sweep Meshing : Complex geometry

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Transition

• Effect of Smooth Transition

• Smooth transition uses advanced front meshing technique

Tetrahedrons Method: Patch Independent

Smooth Transition Off (default) Smooth TransitionOn

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