[KVRC] Khamsin Virtual Racecar Challenge 2016

[Alonso Fan]

Since I'm currently having trouble getting occfd to work, I have installed a student version of Autodesk Simulation cfd, and intend to use this until I can sort out occfd. However I have encountered a slight problem. I cannot import .stl files into the program but I can import SolidWorks part files. (I also have the SolidWorks student version installed). So what I did is saved an stl file from sketchup, then opened it in SolidWorks and then saved it as a SolidWorks part file. Then I tried to import it into simulation cfd. It gives me an error saying that it couldn't import. However when I design something in SolidWorks myself and then import that geometry, it imports fine. Does anyone know why this is the case?

[RicME85]

Try this - http://forum.freecadweb.org/viewtopic.php?t=4783
Convert STL to STEP, apparently STEP is compatible with Autodesk Sim CFD

[Alonso Fan]

Try this - http://forum.freecadweb.org/viewtopic.php?t=4783
Convert STL to STEP, apparently STEP is compatible with Autodesk Sim CFD

Thanks! I'll give it a go later

[RicME85]

@RicME85 I made a mistake and the Amazon AWS instance do not start properly - regardless of the option. I will correct the issue and send you an update. I am sincerely sorry.

I updated occfd to fix the Amazon AWS issue (no other change). Patch 009 can be downloaded from http://www.khamsinvirtualracecarchallen ... .1-009.zip. The Test option should turn around in the usual ten minutes or so.

Test ran normally, finishing within a timely manner.
Ran a full test at the same time and it has just finished so thanks for the fix.
Has cost me £10 so far this month because of the issues

[RicME85]

Something odd with the results.
Total Downforce: -4779.42 N
Front wing(s) downforce: -2817.28 N
Rear wing(s) downforce: -2095.54 N
The wing figures give -4912.82

Also, the 3d view looks like this:

[CAEdevice]

I have already submitted twice... I noticed an important issue with flow detachment in my car, maybe I will submit another update tomorrow.

[julien.decharentenay]

I left my pc on for an 2 hours or so and when I came back, I had a windows firewall prompt asking me if I could allow simplefoam.exe and one of the meshing tools to run. this only happened after simulation 0 and simulation 1 had been completed, and the previous solution had been mapped on to the new mesh. it's weird because occfd had no problem using simplefoam or the meshing tool before in sim0 and sim1.

The windows firewall prompt is because simplefoam is trying to communicate to the other simplefoam process(es). It is important to accept the communication to take place. Normally the firewall remembers this and only prompt once. This happens during simulation 1.

If you are referring to simplefoam from the previous version (from sourceforge), it probably prompted at some point or the openmpi library was somehow already authorised.

Use this happened in simulation 1. I understand and have accepted the exception in firewall. Is this the cause of the error? Because I'm not sure for how long the firewall prompt was on screen before I saw it. My thinking is that it tried to run simplefoam.exe without firewall authorisation and therefore threw out an error?

Thanks for your help btw

If the simpleFoam is not allowed to talk to the other process (ie the exception is not accepted), then it will report an error that it is not able to talk to the other process. I added an option to use the Testing setup in parallel - this should allow you to test the parallel processing without having to seat around for 20 to 30 minutes.

[julien.decharentenay]

Something odd with the results.
Also, the 3d view looks like this:
http://s12.postimg.org/w6jdk4pq4/3dview12.jpg

I am sorry for the lost costs... My mistake... Not sure how I can make up for it...

The 3D view shows that the meshing has meshed both internal and external - which is probably associated with watertightness issues. This cause the pressure on the bodywork to be not very right.

CAEdevice reported the same problem occurring frequently for him. In his case it looked to be associated with small gaps at the joining between the intake and exhaust surfaces and the remaining of the body.

I have some of the entries that I run that show the same issues. When this happens I use netfabb to clean the mesh, and then manually separate the inlet and exhaust surfaces using MeshMixer (from memory). It usually fixes the issue.

[Alonso Fan]

The windows firewall prompt is because simplefoam is trying to communicate to the other simplefoam process(es). It is important to accept the communication to take place. Normally the firewall remembers this and only prompt once. This happens during simulation 1.

If you are referring to simplefoam from the previous version (from sourceforge), it probably prompted at some point or the openmpi library was somehow already authorised.

Use this happened in simulation 1. I understand and have accepted the exception in firewall. Is this the cause of the error? Because I'm not sure for how long the firewall prompt was on screen before I saw it. My thinking is that it tried to run simplefoam.exe without firewall authorisation and therefore threw out an error?

Thanks for your help btw

If the simpleFoam is not allowed to talk to the other process (ie the exception is not accepted), then it will report an error that it is not able to talk to the other process. I added an option to use the Testing setup in parallel - this should allow you to test the parallel processing without having to seat around for 20 to 30 minutes.

Thanks Julien. The error seems similar to last time so I will try the parallel test and I will also try the analysis on single core

[RicME85]

Something odd with the results.
Also, the 3d view looks like this:
http://s12.postimg.org/w6jdk4pq4/3dview12.jpg

I am sorry for the lost costs... My mistake... Not sure how I can make up for it...

The 3D view shows that the meshing has meshed both internal and external - which is probably associated with watertightness issues. This cause the pressure on the bodywork to be not very right.

CAEdevice reported the same problem occurring frequently for him. In his case it looked to be associated with small gaps at the joining between the intake and exhaust surfaces and the remaining of the body.

I have some of the entries that I run that show the same issues. When this happens I use netfabb to clean the mesh, and then manually separate the inlet and exhaust surfaces using MeshMixer (from memory). It usually fixes the issue.

Don't worry about it.

There are a few join issues with the supplied bodywork so not surprised.
Will give Netfabb a go and see what occurs

[CAEdevice]

Hi Julien, sorry to update you so late about my tests related to the "internal mesh" issue. The "merge tolerance" parameter solves the problem if I use a value at least ten times bigger than the one in OCCFD, but if I use a value higher than two or three times some surfaces (es. small rounds, thin regions) are represented badly. So this is not a possible solution.

I obtained good results limiting the refinement (5 5 instead of 6 6). This also produces a lighter mesh (10^6 elements) so I have the suspect that, to obtain the same level of accuracy we have now, we should tweak other parameters (the layer setup for example) too.

I'm quite a beginner with openFoam meshing: I think that other partecipants (Mantium and JJR for sure) could help more than I can do. Anyway: I'm still working on it.

[Alonso Fan]

Try this - http://forum.freecadweb.org/viewtopic.php?t=4783
Convert STL to STEP, apparently STEP is compatible with Autodesk Sim CFD

ok, I've tried this but freecad always goes to a 'not responding' state. I have to force close it through task manager. is there another way?

[RicME85]

how long are you leaving it for as I have the same issue with Sketchup

[Alonso Fan]

Try this - http://forum.freecadweb.org/viewtopic.php?t=4783
Convert STL to STEP, apparently STEP is compatible with Autodesk Sim CFD

ok, I've tried this but freecad always goes to a 'not responding' state. I have to force close it through task manager. is there another way?

I've tried this process with simpler geometry and it works a treat. it seems that the geometry I originally wanted to convert from stl to step, is too complex for freecad to handle in a reasonable amount of time

[RicME85]

It will get there in the end, just have to be patient. I have had to wait 13 hours for Sketchup to import an STL file back when Perrin had their LMP car free to download. Wish I still had the file, would be hand right now, unfortunately lost it with a PC crash