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GridEx Tutorials
Geometric Primitives & Solid Operations
Generic Wing/Body - FELISA Sourcing
Generic Wing/Body - VGRID Sourcing
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Parameter Modification & Regeneration
Transformations & Displacement

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Tutorial I - Geometric Primitives and Solid Operations

  This tutorial demonstrates the creation of geometric primitives and their manipulation using the solid operations described within the CAD/Geometry panel. The objective is to construct an appropriate far-field boundary featuring a spherically blunted cylinder and corresponding solid model for the generic wing/body configuration shown below.
 

  Given the "Generic Wing/Body" sample model for the desired modeling kernel, GridEx is executed.  The model file may be opened as a "CAPrI" type from the file dialog box which is accessed via the File->Open menu.  It may also be simply imported at startup via the -capri command line argument.  For example, assuming the Parasolid modeler is to be used:

    GridEx Parasolid -capri generic
(Note the model file extension is not required here)

We then turn our attention to the construction of the far-field boundary.

  We first create a Box specifying (0,-10,-10) as the corner reference point and (7,10,10) as the box dimensions.  We've deactivated the display of the rotation axes and have also activated the display of the global coordinate axes, the latter of which are rendered in yellow. Note the spherical cap of the configuration has its center at the origin of the global coordinate system.

We now create a Cylinder which extends through the Box by entering coordinates of (-10,0,0) for the first axis reference point, and (15,0,0) as coordinates for he second reference point.  The radius is entered as 5.0 with the resulting cylinder shown above.

It is desired that the portion of the Cylinder which falls within the Box serve as the main section of the far-field boundary downstream of the nose.  To isolate this section, we invoke the Intersect facility where we select the Cylinder as the target volume and the Box as the tool volume.  The resulting solid is shown above. Actually, we could have reversed the order of the selections and achieved the same result.

Note that the rendering of the two initial primitives has been suppressed though they are still accessible from the Structure Tree shown above. Here Volume_1 corresponds to our imported model, Volume_2 corresponds to the initial Box, Volume_3 the Cylinder, and Volume_4 their intersection. We will at this point reinstate the display for the original Box by expanding the Volume_ 2 folder within the Structure Tree and selecting each of the six Faces bounding this solid as shown above. These faces are then rendered by selecting Wireframe under the Style pull-down menu.

Building upon this we then create a Sphere centered at (0,0,0) with radius of 5.0 with the result shown above.  

We now use the Subtract facility to isolate the upstream portion of the sphere by selecting the Sphere as the target volume and the Box as the tool volume.  The resulting volumes consisting of the upstream portion of the Sphere and the central portion of the Cylinder are shown above.

Now using the Unite facility, we select the Sphere as the target volume and the Cylinder as the tool volume with the sum now represented as a single volume entity shown above.

Our next to last step is to introduce a plane of symmetry at the z=0 plane, and to achieve this we define a second Box specifying (-10,-10,-10) as the corner reference point and (10,10,0) as the box dimensions.  The Subtract facility is then used to extract that portion of the solid model external to the Box;  we select the Sphere/Cylinder as the target volume and the Box as the tool volume.    

We then use the Subtract operation once more to remove the volume bounded by the configuration from that bounded by the Sphere/Cylinder volume.  The latter is selected as the target volume and the former selected as the tool volume.  The resulting solid model shown above is ready for meshing operations.


Responsible NASA Official: William T. Jones
Site Curator: William T. Jones
Comments and Questions
Last Updated: Dec 18, 2001