Interactive Meshing of Stereolithography (STL) Complements in FlowVu
STL files have become a sort of de facto standard for importing solids models into FLOW-3D. STL files describe a solid object as a collection of triangles that make up surface of the solid. The convention of STL files is that the vertices of the triangles are output in a clockwise direction around the triangle’s unit normal, which points away from the solid surface.
Frequently, designers will generate solids models of components which modelers are then required to model the flow inside of. For example, a designer may generate a solid model of the flow path through a nozzle rather than the nozzle body. To model the flow through the nozzle, the STL file would be imported as a complement rather than a solid, i.e. flip the surface normals. However, a complement of an STL file appears as a solid block in FlowVu so interactively meshing is not straightforward since the internals of the part are hidden.
One possible solution is to select the object, (double-click on it), right click on it and select Properties, and then make it partially transparent. Now the internals of the part should become visible. However, it’s often difficult to achieve a good balance between transparency and the ability to see regions well enough to mesh them.
A better option is to import the STL as a Solid initially, mesh it interactively, and then switch it to Complement. Switching a part between solid and complement is straightforward using the data tree. Figure 1 shows the STL file NOZZLE.STL imported into the project as a Complement. To the right, the part appears as a opaque box. To change the part to a solid (i.e., flip the normals), click on the word Complement in the tree and select Solid. The display now shows the flow path which will be modeled and is shown in Figure 2.