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GridTool Documentation
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GridTool: A Tool for Structured and Unstructured Grid Generation

Patches

A patch is a closed three-dimensional polygon which is defined by a set of curves. Nonplanar patches should be 3- or 4-sided, and planar patches could be n-sided. Each side of a patch could consist of several curves. Each patch is stored as a link-list of curves. To create a patch, the "Next Patch" button should be pressed. Then, the first curve for the patch must be activated by the user, and then it can be accepted as the first curve by pressing "Accept Edge" button. The subsequent curves can be added by letting GridTool find them. This can be done by pressing "Find Edge" button until the correct curve is found. GridTool will find the next curve within the tolerance define in the " tol" input-field box. Once the correct curve is found, it should be accepted by pressing the "Accept Edge" button. Once a patch is created, its direction can be reversed by pressing the "Reverse Patch" button.

Image of the Patches Panel

Box

This panel is designed to allow the user to create/delete a box. To create a box, press "Create Box" button which will create a box bounded by minmax in x, y, z coordinates defined in the six input-fields in the panel. The resulting curves and patches are grouped together as the "Box" family. To delete the box, press the "Delete Box" button which will delete all patches and curves in the "Box" family.

Image of the Box Creation Panel

FAQ

How do I create a patch?
  1. Select a family name
  2. Select a boundary condition
  3. Push the Next Patch button
How do I make an existing patch active?
Either enter the patch number in the Patch # input-field, or place the cursor over the patch and hit the f key
How do I select the patch boundary condition?
  1. Put the cursor over the BC input-field
  2. Use the right mouse to display and select the boundary condition
  3. Every time a new patch is created, it will (by default) be associated with the values of the BC and family that were in the buffers at the time. In order to change the BC and/or family association of an existing patch, make the patch active and press the "Apply BC/Family" button after having entered the desired family and BC values.
How do I create patches automatically?
  1. Turn the surfaces on
  2. Select a family name (e.g. front-fuse)
  3. Select a BC, use the right mouse
  4. Select numbers of patches in each directions
  5. Press the Auto Patch button
How do I reverse/delete an existing patch?
Make the patch active and press the reverse / delete button
How do I delete a family of patches?
Select the family name from Family input-field, the press Delete Family button
How do I associate a patch and a set of surfaces?
Make the patch active, turn the surfaces on, push the Accept Surfaces button
How do I split a patch?
  1. Make the patch active
  2. Create a curve that splits the patch
  3. ake the curve at which to split the patch active
  4. Press the Split Patch button
How do I add an edge to an existing patch?
Either make the curve active or use the Find Edge to find the next curve, then press Accept Edge button
How do I make an existing edge active?
Use the input-field Edge #
How do I find the next edge?
Push the Find Edge button
How do I reverse/delete/connect an edge?
Make the edge active, then press the button
How do I split an edge?
Make the splitting point active, the press the Split Edge button
How do I convert a 3 or 4 sided patch to a NURBS surface?
Make the patch active, and then push Patch to Surface button
How do I automatically create a box which covers the geometry?
Push the Box button which opens a panel, enter the minmax of the Box, press the Create Box button
How do I fix directions of all patches automatically?
Select one patch with the correct direction, then press Fix Patches button
How do I change a patch type?
Enter the type into the Patch Type input-field
How do I get more information for a patch?
Activate the help from main panel, press the Bad Patches button, then move the cursor over the Bad Patches button, the information for the active bad patch will be displayed
How do I turn on/off patches?
Use the All Patches button
How do I check to see if there are any bad patches?
Press the Bad Patches button, then the bad patches will be displayed
What are bad patches and how can I fix them?
A patch is bad if
  1. a curve is used more than twice (this may not create a problem), or a curve is used twice in the same direction (to fix you can reverse the edge direction of the bad patch)
  2. patch is not closed (either there is a gap between the edges or the tol is low, use collapse points in Points and Curves Panel to fix it)
  3. the patch is n-sided and it is not a planar patch (the patch may be slightly off the plane, this depends on the tol)
  4. no surface is associated with the patch (FELISA)
  5. not enough points for the patch
What is the shrink panel for?
The patch can be shrunk for the display purposes. This will not effect the data.
How can I create a symmetry patch (two loops)??
  1. make the patch on symmetry active (this is often one side of a box)
  2. make one of the curves on the body/symmetry active (second loop)
  3. accept that curve as a edge
  4. make sure the direction is OPPOSITE to the patch boundary in this case. The final patch will have two loops: (1) outer loop from the box, (2) the inner loop from body/sysmmetry.
  5. continue accepting all the curves on the symmetry until the second loop is closed as well.
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Last Updated: Sep 17, 2002