Insight the FRIENDSHIP-Framework

STL

CAD interfaces towards mesh generators quite often create problems if one has to rely on exchange formats like IGES, Parasolid or similar, especially if the number of individual surface patches is high, like a typical IGES export from NAPA. Within the research project FORM-PRO and a number of in-house activities new triangulation methods have been implemented and made available to our users in release 2.3. These new functions allow configuring rules for grouping many surface patches to one region and export these regions either in a colored STL-file or in several ASCII STL-files. Further processing options have been implemented to extrude the surfaces representations to solids and enable Boolean operations for a CFD-ready preparation of the fluid domain.

Tesselation of twin screw vessel

Since most surface compounds are not fully watertight, snapping and control algorithms can be configured within the FRIENDSHIP-Framework and executed automatically for each design variant. The accuracy of the tessellation and the tolerance to overcome gaps can be user defined and even parameterized so as to prepare the STL export as accurate as needed to meet the demands of the subsequent simulation.

Healing gaps and removing hanging nodes

The entity introduced for merging several surfaces into one group of triangles is called Trimesh and can be found in the Menu Create | Meshes and Solids. The user simply selects one or several surfaces in a logical sequence and creates a Trimesh. Adding further surfaces to the set can be realized by drag and drop: holding the left mouse button pressed down on an object in the 3D view or in the object tree and drop those on the Trimesh entity will merge the full set. Please give it a try.

Adjusting accuracy

Once the Trimesh is complete additional processing options can be activated e.g. to make a solid body from the hull surface. The postprocessing options can be configured in the ObjectEditor once the Trimesh is selected. For various applications the extrusion is one of the most often applied functions. For a hull form an extrusion to the centerplane comes natural if symmetry of flow is assumed. The picture below shows a fully processed hullform that has been imported from Maxsurf via an IGES file. The trimming of the deck and the hole for the bow thruster have been realized in the Framework after configuring the STL options for a watertight CFD model. In the same way as the hole is cut into the hull, appendages can be easily added to the model. Parametric studies on the properties of rudders, shaft brackets or energy saving devices can now be easily conducted, since the pre-processing of the CAD model is tailored to your mesh generator’s needs. If you are interested in streamlining your CFD design process, please let us know. We would be happy to support you in realizing a fully automated process chain.

Thruster hole and trimmed deck

Read more about the capabilities of the FRIENDSHIP-Framework here.

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