Panel flow over an aircraft
Hi. I'm pretty new to Caedium, and I've been having some issues trying to model the coefficient of pressure over an aircraft body, which I imported as an STL file. I based the conditions in use off the tutorials available on this website, ie. only specifying fairly limited variables air/ linear velocity/ accuracy. However, when I attempt to map the pressure coefficient I get this error:
Warning:
stl_0_18 [www.1901.4] Triangulator: Failed: Edge already in front
stl_0_15 [www.1892.4] Triangulator: Failed: Front progress failed: 15 edges remain
Warning:
stl_0_14 [www.1888.4] Triangulator: Failed: Edge already in front
I was wondering whether there was a baseline set of conditions I could use to gain a basic map, or whether there's something wrong with the model itself. I've tried using a number of models online to see whether the issue does stem from my modelling abilities but I get similar problems, implying I'm probably doing something wrong on the Caedium side. Any advice would be massively appreciated. Thanks.
Feedback
Questions? Ideas? Problems?
STL is a poor format
The error indicates that the meshing failed.
STL is a poor format for geometry transfer. If you have the option I recommend using STEP (.stp). For more details see "CFD Prefers NURBS Over STL".
When you are forced to use STL you need to ensure that each geometry edge is connected to exactly two geometry faces. Use the Edges->Connect on the Geometry Tool Palette.
The groups (faces) of facets need to be separated at sharp features in your modelling software.
Connected Geometry
Thanks for the quick response. I'm transferring via Blender, so I'm sort of stuck with STL, but I have tried .obj with little success. I followed the Edges->Connect suggestion to create a connected geometry, but I'm still receiving a similar error:
face_189 [www.70711.4] Triangulator:
Failed: Front progress failed: 5 edges remain
face_109 [www.63316.4] Triangulator: Failed: Zero length edge (+ similar)
Do you think my model is too complex to be resolved by the connect tool, or do you reckon I missing something glaringly obvious.. Thanks again.
Start simple
I would suggest starting with a simple model and adding complexity in stages. Blender is a faceted modeler, so for aerodynamic shapes (curves) you would be better served using a CAD tool and STEP (.stp) export.
Question
Without trying to sound too blunt, does this mean that the model I've created in Blender will simply not work with Caedium, meaning I'll have to try and recreate it from scratch (quite a long process)? Something that seems a little odd is that similar attempts with the model found here http://www.symscape.com/node/526 seem to have similar issues: I presume that this model would not hold and geometry related issues my model may incur, so is there a possibility my setting/something else may be the issue. Thanks again.
Faceted models
Without seeing your model I can't determine if it's suitable for Caedium.
Blender is a great graphics and animation package for making realistic models that look good. For simulation to work the model has to be coherent and manifold, which means you can't have a wing go straight through a fuselage. The wings have to join the fuselage at well defined junctions, i.e., all the faces have to align along edges and be watertight. Ideally you want curves to maintain their curvature and not be faceted.
Having said all that, often faceted models (produced by Blender, SketchUp, etc.) can be used in simulations, but they take more effort to configure (e.g., clean up and de-feature) than those produced by genuine CAD tools.
For any simulation software (e.g., CFD) there is a learning process that isn't always easy, especially if you decide to take on a complex model without first achieving success on simpler models and figuring out a process that works for you. I doubt you jumped straight into Blender with a complex model as your first project, simulation software is no different.
You do have the option to purchase a Caedium Professional subscription for one-on-one help. The intent of the free trial is to learn some basic skills following the Caedium tutorials and then decide whether to proceed to production work with a paid, supported subscription.