SimScale CAE Forum

'A-Class Mk6' simulation project by lmuehrke


I created a new simulation project called 'A-Class Mk6':

It is my final attempt to test this hier

More of my public projects can be found here.


Hello @lmuehrke, could you explain a little what you are trying to analyize? I would be happy to assist if i can. It seems that there is something odd with your geometry. The bounding box has a size of 2e100m. What would the actual dimensions be? Which CAD tool did you use to create/export the geometry?


I want to analyize an hull model.
I build it in Sketchup but convert it in Rhino3d.
The mesurments are ca. 5490 ; 2300 ; 600 (millimeter).

In Rhino i had the problem, that the hull seams not to be closed (Hope that santence make sense)

Did you have an Idea? (how to fix it?)


Building a model in Sketchup which is later to be used in a simulation is not something that I would personally recommend. Going from an STL to a BREP model should be avoided, whereas the other way around is fine.
I just cleaned the model from some additional “edges” which were causing this huge scale and also one solid was double.
You can have a look at the cleaned model here.

Concerning the meshing and simulation setup, I would ask @dheiny or @gholami for some suggestions as I am rather a solid mechanics guy and have only limited experience with CFD.


Thank you!

But sadly this was the wrong model… (it was my fault)

all the files are in Step… as I mentioned before I build them in Sketchup, but convert with Rhino before I start to test them. Had a few problems with STL Files.
Rhino could open .skp (SketchUp nativ) and translate it in Step or is this also bad?


@dheiny Hallo,
Ich habe Probleme mit der Erstellung eines funktionierenden Meshs.

Ich erstelle die Modelle mit SketchUp und konvertiere es zu einer .step Datei mit Rhino3D. Gibt es eine Möglichkeit das zu ermöglichen?

Das gesamte Projekt geht um einen A-Class Katermaran, Ich möchte vorerst Fluid Dynamic Test durchführen um die Hydrofoils und den Rumpf auf ihr Verhalten im Wasser und in der Luft zu testen.
Auch möchte ich eine FEA durchführen um mein Laminat plan erstellen zu können.


@lmuehrke, interesting simulation project you’re working on there! I think the problem with your geometry creation workflow is that somewhere in the process, only the faceted model is kept and the NURBS are lost. I had a similar situation in this thread: Collaborative simulation project? Multiphase flow around a boat hull. You can see this by the many, many small individually selectable faces of your model, which is probably only a couple of faces in SketchUp. So you basically seem to have here a STEP file that does not contain more information than a STL file.

Depending on what kind of CFD analysis you want to run there are different options now how to solve this. What kind of analysis do you want to run with the catamaran? A single phase flow of water around the bottom hull? A single phase flow of air around the top of the boat or a fully-fledged two-phase flow simulation including the air-water surface around the full boat? BTW there are also different public project of interest here:

I would recommend starting with a simple analysis, say a single phase flow if you agree. For this, a simple STL file of the part that you want to analyze is enough. So just export the model directly from Sketchup to STL and upload it to SimScale. Then you can use the “Automatic SnappyHexMesh for external flow” mesh operation to generate a mesh for the water domain around it. This analysis has the inaccuracy that it does not model the correct behavior of the fluid-water interface since this interface is artificially kept “straight”. But generally, I think starting with a simple analysis, getting that one right and then moving on to more complex is oftentimes a good choice in the very beginning.

Hope this helps as a first step!


@rszoeke how did you repair the “Test” file, it is the only one that is able to build a mesh of… :confused:

also @dheiny I try to export just the NUMBRS Data, witch seem to be lost (mention in your Post) But it does not work eigther… :confused:

And the first steps are a Singel flow Analysis around the Hulls, (Partly with water and Full with Air).

An STL Dose not work, (In non of the methodes I tried)

Or did you know wich one I could ask to translate it into a working file?!


@lmuehrke, I only imported it to a CAD tool (Salome) removed the duplicate solid, and exported only the solids as a compound. As I wrote above, the main problem was that there were some free “edges” that totally distorted the length scale of your model to 1e100m.
You can try Salome yourself, since its open source, but I guess any other CAD software would also be OK.