dm-intro 16.0 l06a geometry modeling for cfd

7/24/2019 DM-Intro 16.0 L06A Geometry Modeling for CFD

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Lecture 6A:

Geometry Modeling For CFD

Introduction to ANSYS Design


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In this lecture we will learn about:

Fluid Body Extraction

Internal

External

Symmetry Modeling

Watertight Body Preparation & Conformal Meshing

Surface Extensions

Connect

Use of Lines and Sketches for CFD Modeling

Zero Thickness Surface Modeling

Geometry Modeling for CFD


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Preprocessing Workflow

Import/Geometry

Creation

GeometryModifications

Meshing

Sketches and Planes

Geometry Import

Options

3D Operations

Bi-Directional

CAD/ Neutral

Geometry Cleanupand Repair

Automatic

Cleanup

Simplification,

Mid-surface,

Fluid Extraction

Extrude, Revolve,

Sweep, etc

3D Operations

Booleans,Decompose, etc.

Meshing Methods

Hybrid Mesh: Tet,

Prisms, Pyramids

Hexa Dominant,

Sweep meshing

Global Mesh

Settings

Local Mesh Settings

Sizing, Controls,

etc.

Assembly

Meshing


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Fill

Creates internal fluid volume

Two options By Cavity : user must select all wetted surfaces

By Caps : user must create closing surfaces at

inlets and outlets, and select bodies

Details View of Fill

Internal fluid volumeextracted using Fill

Cap surface bodies
http://localhost/var/www/apps/conversion/tmp/scratch_5/movies/fill_by_cavity.swf


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Enclosure

Creates enclosure around the bodies

Useful for external aerodynamic analysis

Can be used for extracting internal flow domain

Input

All or selected bodies

Shape of enclosure

Extent of enclosure

Output

A frozen body around the selected parts with specified extents

Internal flow volume as a result of automatic Boolean subtract

Supports symmetry models

Full or partial models can be included in enclosureEnclosure cre


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Enclosure: External Flow Example

Model

Using Symmetry

User Defined Shape

Enclosure


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Symmetry

Defines symmetry for the model

Input

All or selected bodies

Up to three symmetry planes

Operation

Symmetry planes slice the model

Output

Sliced model (part lying on the positive side of the axis is retained)

Details View of

Note: Faces that a

the symmetry pla

Symmetry namUsing Symmetry

Tip:

as vis

disco

(aftesupp


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Surface Extension

Allows extension of surface bodies to the desired extent

Extension type

Natural: Based on gradients of selected edges

User Defined: User specifies the direction

Model with gap Model with ga

Details View of Surface

Extension
http://localhost/var/www/apps/conversion/tmp/scratch_5/movies/surface_extension_natural.swf


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Connect

Aligns and possibly joins a set of

Vertices

edges

faces

Properties

Location property

T-junction property

Details

Vertex Connect


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Connect: Edge Connect Example

Model with a gap

Location:

Interpolated

Location:

Preserve First

Both edges moved to interp

Second edge moved to first


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Connect: Edge Connect Example T-junc

Model with a gap


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Connect After Shared Topology

Connect featurecan be used afterthe Shared Topology feature

to selectively share faces between two bodies of a multibody

part. This can be used to:

Fix face sharing failures after Shared Topology

Can be used for selective sharing of faces in conjunction with

Selective Shared Topology

The advantageof Connect feature is that

It takes user defined tolerances to Connect faces which

failed due to smaller Shared Topology tolerance

This ensures conformal meshing

Please be careful in choosing tolerance value, as high

values may result in deformation of model at some places


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Concept Modeling Tools

Why is Concept Modeling(Lines and Faces) relevant for CFD users?

Sometimes the imported files contain issues like: Missing Faces

Corrupt Faces

Details which require cleanup by selective geometry recreation

For cleaning, patching, recreating surfaces & stitching a water tight body, s

surface creation options of concept modeling are used

CFD models also require some solids/thin bodies to be modeled as ze

surfaces

Examples are baffles, fins, zero thickness pipe walls, fan shrouds, etc.

For above mentioned cases mid-surfacing tools need to be used

Sometimes 2D modeling operations also require use of concept mod


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Lines from Points

[Main Menu] Concept Lines From Points

Points can be any

2D sketch point

3D model vertex

Point Feature (PF)

A point segment is a straight line connecting

two selected points.

The feature can produce multiple Line Bodies,depending on the connectivity of the chosen

point segments.

Point 1

Line Body


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Lines from Edges

[Main Menu] Concept Lines From Edge

Creates line bodies based on existing 2D and 3D model edges

Can produce multiple line bodies depending on the connectivity

of the selected edges and faces

Can select edges and/or faces through two fields in the detail

window then Apply

Line Bodies


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Split Edges

[Main Menu] Concept Split Edges

Splits edges (including line body edges) into two or more pieces Fractional: Value of 0.5 splits the edge into two edges of equal length

Split by Delta: Distance between each split is given by Delta along the

edge.

Split by N: Number of Divisions of the Edge

By Split Location: By Fraction or By Coordinates

Selected line Fraction = 0.5 Fraction = 0.25

Fractional:


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Surfaces From Edges

[Main Menu] Concept Surfaces from Edges

Creates surface body using existing body edges,including line body edges as the boundary

Can be solid or line body edges

Edges must form non-intersecting closed loops

Each closed loop creates a frozen Surface Body

The loops should form a shape such that a simplesurface can be inserted into the model as

planes, cylinders, tori, cones, spheres and

simple twisted surfaces

Twisted surface


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Surfaces From Sketches

[Main Menu] Concept Surfaces from Sketches

Creates surface bodies using sketches as boundaries(single or multiple sketches are OK)

Base sketches must be closed profiles which are not

self-intersecting

May choose to Add or Add Frozen operations

Can reverse normal direction No in Orient WithPlane Normal field

Can enter thickness which will be used in creating

the FE model


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Mid-Surface

Extracts surface body that is midway between existing

solid body faces

Two Options:

Manual: Operates only on user specified face pairs

Automatic: Provides option to search for other

matching face pairs

Details View of Mid-SurfaceMid-Su

p


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Summary

What have we learnt in this session?

Fluid Body Extraction

Symmetry Modeling

Watertight Body Preparation & Duplicate Face Removal

Modeling of Lines and Surfaces for Simplification/Repair


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Workshop 6.1AGeometry Cleanup &Extraction


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Micro-Workshop: 2

Objective:

Create an Enclosure for extracting external fluid region

dm-intro 16.0 l06a geometry modeling for cfd

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