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tutunint [2012/02/17 09:25]
ramcdona
tutunint [2018/04/01 14:41] (current)
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 ====== Unintersected Component Wireframes ====== ====== Unintersected Component Wireframes ======
  
-This component ​of the Cart3D tutorial will walk through the process of generating an unintersected component wireframe in VSP and then using Cart3D'​s intersect utility to process the geometry into a single watertight body.  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 [[OneraM6|geometry generation]] phase of the tutorial or you can download a ready-to-go [[http://www.openvsp.org/​files/OneraM6.vsp|Onera M6 geometry]].+This installment ​of the Cart3D tutorial will walk through the process of generating an unintersected component wireframe in VSP and then using Cart3D'​s intersect utility to process the geometry into a single watertight body.  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 [[OneraM6|geometry generation]] phase of the tutorial or you can download a ready-to-go [[http://hangar.openvsp.org/​vspfiles/108|Onera M6 geometry]] ​from the VSP Hangar.
  
-Although Cart3D'​s intersect tool is very robust, there are some cases it does not handle. ​ One of these cases is when surfaces of two components ​are perfectly coincident. ​ This situation occurs at the wing root of the Onera M6 model created in the tutorial; the root surface of the left and right wing halves are perfectly coincident.+Although Cart3D'​s intersect tool is very robust, there are some cases it does not handle. ​ One of these cases is when surfaces of two parts are perfectly coincident. ​ This situation occurs at the wing root of the Onera M6 model created in the tutorial; the root surface of the left and right wing halves are perfectly coincident.
  
-One common fix for this situation would be to move the components ​slightly (say 10^-6) in the spanwise direction so the root surfaces are no longer coincident. ​ Since the wing roots are normally buried inside a fuselage component, the gap between the wing halves would be insignificant. ​ However, the Onera M6 geometry has no fuselage and any positive offset would result in a gap between the wings and any negative offset would result in intersection artifacts at the wing root.  Furthermore,​ demonstrating the intersect tool with two components ​that don't really intersect is not very useful.+One common fix for this situation would be to move the parts slightly (say 10^-6) in the spanwise direction so the root surfaces are no longer coincident. ​ Since the wing roots are normally buried inside a fuselage component, the gap between the wing halves would be insignificant. ​ However, the Onera M6 geometry has no fuselage and any positive offset would result in a gap between the wings and any negative offset would result in intersection artifacts at the wing root.  Furthermore,​ demonstrating the intersect tool with two parts that don't really intersect is not very useful.
  
-Consequently,​ for this part of the tutorial, a pod component will be added to the geometry to play the role of a fuselage in the model. ​ This obviously would not be appropriate for matching the Onera M6 wind tunnel results, but it should do well for the purposes of this tutorial.+Consequently,​ for this installment ​of the tutorial, a pod component will be added to the geometry to play the role of a fuselage in the model. ​ This obviously would not be appropriate for matching the Onera M6 wind tunnel results, but it should do well for the purposes of this tutorial.
  
 ==== Generating an Unintersected Component Wireframe ==== ==== Generating an Unintersected 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.
  
   - Onera M6 start   - Onera M6 start
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   - Refine airfoil points   - 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.      * 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 [[MeshOverview|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.
      - In the 'Multi Sect Wing Geom' window, under the '​Gen'​ tab, enter 101 in the box to the right of 'Num Points:'​ \\ {{:​1_airfoil_points.png?​direct&​200|}}      - In the 'Multi Sect Wing Geom' window, under the '​Gen'​ tab, enter 101 in the box to the right of 'Num Points:'​ \\ {{:​1_airfoil_points.png?​direct&​200|}}
   - Refine spanwise wireframe   - Refine spanwise wireframe
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      - From the displayed list of export options, choose '​CART3d File (.tri)'​. ​ Unintersected triangulated meshes must be written in TRI format.\\ {{:​4.5_export_options.png?​direct&​200|}}      - From the displayed list of export options, choose '​CART3d File (.tri)'​. ​ Unintersected triangulated meshes must be written in TRI format.\\ {{:​4.5_export_options.png?​direct&​200|}}
      - In the '​Select File' dialog, navigate to the save location and choose a file name.  When you are satisfied, click '​Accept'​. \\ {{:​5_pick_file.png?​direct&​200|}}      - In the '​Select File' dialog, navigate to the save location and choose a file name.  When you are satisfied, click '​Accept'​. \\ {{:​5_pick_file.png?​direct&​200|}}
-     * After the export has completed, VSP will display the unintersected mesh that was created on-the-fly. \\ {{:​6_after_export.png?​direct&​200|}}+     * After the export has completed, VSP will display the unintersected mesh that was created on-the-fly.  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. \\ {{:​6_after_export.png?​direct&​200|}}
      * Zooming in on the nose-region of the model demonstrates that no intersection or trimming operation has been performed. \\ {{:​7_unintersected_proof.png?​direct&​200|}}      * Zooming in on the nose-region of the model demonstrates that no intersection or trimming operation has been performed. \\ {{:​7_unintersected_proof.png?​direct&​200|}}
   ​   ​
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 Once you have successfully intersected the model, continue to the [[TutSetup|Cart3D Setup Tutorial]]. Once you have successfully intersected the model, continue to the [[TutSetup|Cart3D Setup Tutorial]].
  
 +Or, feel free to jump to your topic of choice.
  
 +  - [[OneraM6|Geometry Generation]]
 +  - [[MeshOverview|Mesh Generation]]
 +    * [[TutGenMesh|Isotropic Generated Mesh]]
 +    * Unintersected Component Wireframe (This Page)
 +    * [[TutCompGeom|Intersected Component Wireframe]]
 +  - [[TutSTLtoTRI|STL to TRI Conversion]]
 +  - [[TutSetup|Cart3D Setup]]
 +  - [[TutRunCart3D|Cart3D Execution]]
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