Mesh Preparation and Output to Solver

Edit Mesh

Usage of Edit Mesh tools

-To diagnose and fix any problems and improve mesh quality

-To convert element types

-Refine and/or coarsen mesh

-Manual and automatic tools

-For imported as well as internally created mesh

Mesh Checks

To diagnose mesh associativity problems

-Errors–most likely to cause problems in:

Solver translation

Solver input

Solution convergence/run

-Possible Problems – “Unclean surface mesh”

Unwanted elements

Unwanted holes/gaps

May result in incorrect solution

-Can check any combination of errors/possible problems at any one time

Individually select

Click on Error or Possible Problems tabs will select all options in column – selecting again will de-select all

Set Defaults will select most commonly seen/detrimental diagnostics

-Check Mode

Create Subsets–creates a subset of elements that fit each criteria

Check/Fix Each–offers automatic fixing of indicated problem

Mesh Checks: Mesh Errors

-Duplicate Elements

Elements that share all nodes with other elements of the same type

-Uncovered Faces

Volumetric element faces that are neither attached to the face of another volumetric element nor to a surface element (boundary face)

-Missing Internal Faces

Volumetric elements that are adjacent to another of a different part with no surface element between them

-Periodic Problems

Inconsistency in the number of nodes/faces between periodic sides

Special check for rotating (sector) or translational periodic grids

-Volume Orientation

Left handed elements due to incorrect connectivity (node numbering of cell)

-Surface Orientations

Volume elements that share the same surface element (overlap)

-Hanging Elements

Line (bar) elements with a free node (node not shared by another bar)

-Penetrating Elements

Surface element(s) that intersect or penetrate through other surface elements

-Disconnected Bar Elements

Bar elements where both nodes are unattached to other bars

Mesh Checks: Possible Problems

-Multiple Edges

Surface elements with an edge that shares three or more elements

Can include legitimate T-junctions

-Triangle Boxes

Groups of 4 triangles that form a tetrahedron with no actual volume element inside

-2 -Single Edges

Surface element with 2 free edges (not shared by another surface element)

-Single-Multiple Edges

Surface element with both free and multiple edges

-Stand-Alone Surface Mesh

Surface elements that don't share a face with a volumetric element

-Single Edges

Surface elements with a free edge

Can include legitimate hanging baffles

-Delaunay Violation

Tri elements with nodes that are within the circumsphere of adjacent elements

legacy quality criteria

-Overlapping Elements

Continuous set of surface elements that occupy the same surface area (surface mesh that folds on to itself)

-Non-manifold vertices

Vertices whose adjacent elements’ outer edges don't form a closed loop

Typically found in tent-like structures where surface elements jump from one surface to another across a narrow gap or sharp angle

-Unconnected Vertices

Vertices that are not connected to any elements

Usually eliminated automatically upon saving the mesh

Mesh Checks

If Create Subsets was selected

-Will go through all checked criteria at once

-Elements that have a particular error/problem are put into a subset with that diagnostic type name

-Subsets activated in Model Tree

.Turn off all parts or shells to view subsets

If Check/Fix Each was selected

-Will be prompted with options one criteria at a time

Fix: Automatically fix the error/problem

-Recommended only for Duplicate Elements, Volume Orientations, Periodic Problems, Overlapping Elements

Create Subset

Ignore

-For example, multiple edges may be legitimate t-junctions; single edges – legitimate free edges

Mesh Smoothing

Automatically improve element quality

-All element types

-Necessary to have geometry loaded

-Nodes are moved to improve the element quality

Automatic node movement constrained by node projection type to geometry type – e.g. curve nodes will be constrained to move only on curves

-Histogram is automatically displayed/updated after smoothing

User chooses:

-Criterion

-Smooth Mesh Type

Smooth: Element types actively smoothed; quality of type appears as part of histogram.

Freeze: Nodes are held in place during the smoothing process; elements not in histogram

Float: Nodes can be moved along with adjacent smoothed elements, but quality ignored; not shown in histogram

Example: Freeze Prisms and Pyramids while smoothing Tetra. Float surface elements

Advanced Options

-Smooth Parts/Subsets

Smooth all parts, visible parts (activated in model tree), or visible subsets

Quick, local smoothing

-Laplace smoothing

Gives more uniform mesh size relative to neighboring elements

Recommended for TRI only – smooth Tetra after with Laplace turned off

Recommended prior to prism generation

-Not just worst 1%

Factors in all elements instead of only the worst 1% of those beneath quality value and their neighbors

-Violate geometry

Unconstrain nodes slightly from geometry within user defined tolerance – absolute or relative to minimum edge length of mesh elements

Output

ANSYS ICEMCFD Allows you to write input files for many CFD and FEA solvers. The output tab can be used to,

-Select solvers

-Define boundary conditions

-Edit parameters

-Write input file

Wing Edit Workshop

Compute Mesh

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