Mech_Intro2_14.0_L05_VirtTopo

8/12/2019 Mech_Intro2_14.0_L05_VirtTopo

1/13

2011 ANSYS, Inc. March 28, 20121 Release 14.0

14. 0 Release

Introduction to ANSYS

Mechanical Part 2

Lecture 5

Virtual Topology


2/13


Chapter Overview

Virtual topology was introduced in the Mechanical Introduction Part 1 course.

In this chapter we extend the coverage of that topic:A. Virtual Topology

B. Defining Virtual Topology

C. Virtual Split Entities

D. Virtual Hard Vertices

E. Editing Virtual Topology

F. Meshing Implications


3/13


A. Virtual Topology

Virtual topology is a feature that can aid you in reducing the number of elements

in the model, simplifying small features out of the model, and simplifying load

abstraction.

For meshing certain CAD models you may want to group faces and/or edges togetherallowing you to form virtual cells in order to reduce or improve the elements.

You can split a face to create two virtual faces, or split an edge to create two virtual

edges for improved meshing. A virtual cell in Mechanical modifies the topology of the local copy in Mechanical.

Your original CAD model remains unchanged.

Several examples follow to illustrate virtual topology . . .


4/13


. . . Virtual Topology

This example shows 3 surfaces

selected and combined into avirtual cell.

Here 3 edges are selected to

form a virtual edge.


5/13



In this example one edge of this multibody

part has a size control assigned whichcauses irregularities in the overall mesh.

Shown in the upper right, 3 edges are

virtually split to accommodate improved

elements shapes.

Initial Mesh

Final Mesh

Virtual Split Edges

Size Control


6/13



Consider the example below:

Virtual

Cell


7/13 2011 ANSYS, Inc. March 28, 20127 Release 14.0

B. Defining Virtual Topology

Virtual Topology branch is added below the Model

branch:

Individual virtual entities do not appear in the tree.

Instead, a statistics section in the details lists virtual

entities.

An automatic virtual topology function will attempt tocreate virtual cells based on the details settings.

Automatic Virtual Topology: Low, Medium, High: Indicates how aggressively

virtual topology will be searched for.

Edges Only: Searches for adjacent edges to be

combined.



. . . Defining Virtual Topology

Virtual Cells can be created manually:

Select the entities (faces shown here) to be included in the virtual cell. Choose Merge Cells in the context menu (or RMB > Insert > Virtual Cell).



C. Virtual Split EntitiesIn some instances it may be desirable to split a face to allow a specific meshing

operation.

With the Virtual Topology branch

highlighted, select 2 vertices as the desired

split point.

Choose Split Face at Vertices to complete

the operation. Vertex selection may be comprised of

existing vertices or virtual hard vertices

can be created (see following slides).

Note, selected vertices must both beassociated with the face to be split.



. . . Virtual Split EntitiesVirtual split faces can be accomplished by creating virtual split edges (note the split

faces utilize the vertices generated when the edges are split).

Virtual Split Edge at +: splits at

the selection point along the

edge.

Virtual Split Edge: requires a

fractional entry indicating the

position along the edge where

the split will be located (e.g. 0.5results in the line split in half).


11/13


D. Virtual Hard VerticesA Virtual Hard Vertex feature allows the creation of hard points which can be

used to split faces where no natural vertex exists.

With the Virtual Topology branch highlighted

select the face where the hard vertex is to be

located.

Note, a +sign will appear at the cursorlocation.

Choose Hard Vertex at + (or RMB > Insert

> Virtual Hard Vertex at +).


12/13


E. Editing Virtual Topology

Virtual entities can be reviewed, edited or deleted

from the context toolbar (highlight Virtual Topology

branch):

Use the arrow keys to cycle through next/previous

virtual entities.

The virtual entity is highlighted graphically and the

status bar (bottom of graphics window) indicates thecurrent selection.

The Edit icon allows access to an editor window

where modifications to the virtual entity definitioncan be made.

Use Delete to remove unwanted virtual entities.


13/13


F. Meshing ImplicationsKeep in mind that the topology can change!

Example: a chamfer is added to the top surface in this virtual cell. The interior lines are

not recognized anymore.

Mesh using virtual

topology

Original mesh

Elements edge is shown as a solid

line and the original chamfer and top

surface is shown as a dotted blue line.

The chamfer representation is no

longer present.

Mech_Intro2_14.0_L05_VirtTopo

Documents

Transcript of Mech_Intro2_14.0_L05_VirtTopo