Table of Contents

Intersected Component Wireframes

This installment of the Cart3D tutorial will walk through the process of generating an intersected component wireframe in VSP. If you haven't built the Onera M6 wing, or you don't have your own geometry to analyze, you should go back to the geometry generation phase of the tutorial or you can download a ready-to-go Onera M6 geometry from the VSP Hangar.

Generating an Intersected Component Wireframe

As you proceed through the tutorial to mesh the Onera M6, remember that images have been included as thumbnails, so any place you see a picture, click on it for a larger version.

  1. Onera M6 start
    • Start with the Onera M6 model from the end of the model building tutorial.
  2. Refine airfoil points
    • The triangulated wireframe is created by connecting the diagonals of the quadrilateral wireframe shown on screen. Consequently, the resolution of the triangulated wireframe is determined by the resolution of the quadrilateral wireframe shown on screen.
    • As discussed in the Mesh Generation discussion of the tutorial, Cart3D has unique mesh resolution and quality requirements which make it particularly well suited to VSP and this approach.
    1. In the 'Multi Sect Wing Geom' window, under the 'Gen' tab, enter 101 in the box to the right of 'Num Points:'
  3. Refine spanwise wireframe
    1. Select the 'Sect' tab and then click one of the right-facing arrows under 'Num Interpolated XSecs' until there are 40 interpolated cross sections.
  4. Intersect components
    • VSP has the ability to intersect the triangulated wireframe components resulting in a single watertight body for a model. In addition to providing input for high-fidelity analysis, this capability is commonly used to quickly calculated the wetted areas and volumes of a model.
    1. From the 'Geom' menu, click 'CompGeom (Union)…'
    2. When the 'Comp Geom' window opens, click 'Execute' at the bottom of the window.
    • When complete, a wetted area and volume report will be displayed in the 'Comp Geom' window; this window can now be closed. Notice in the 'Geom Browser' that VSP also added an intersected component mesh to the model. The mesh shown on screen exactly corresponds to the information written to the file. Note that the original geometry components are still present, but they have automatically been hidden.
  5. Export intersected file
    • An intersected triangulated surface can be exported from VSP after CompGeom has been executed.
    1. From the 'File' menu, select 'Export…'.
    2. From the displayed list of export options, choose either 'CART3d File (.tri)' or 'Sterolith File (.stl)'.
    3. In the 'Select File' dialog, navigate to the save location and choose a file name. When you are satisfied, click 'Accept'.

Generating an Intersected Wireframe from the Command Line

The VSP interface is the best way to set up and adjust the wireframe resolution, but once that is established, you may want to generate the wireframe from the command prompt.

To generate an intersected triangulated wireframe from the command line, enter the following command:

vsp -batch infile.vsp -compgeom -tri

or

vsp -batch infile.vsp -compgeom -stl

These commands will generate the unintersected wireframe and write 'infile.tri' or 'infile.stl', respectively.

Next Steps

Once the intersected wireframe is complete, the next step is to prepare the file for analysis in Cart3D. If you are using a STL file, it will need to be converted to a Cart3D TRI file; that process is detailed in the STL to TRI Tutorial. Otherwise, continue to the Cart3D Setup Tutorial.

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