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julien.decharentenay 08-29-2013 01:24 AM

CFD expert - first time posting

I have found quite a lot of very interesting information through the form and website - particularly I was looking for Cd and Cl information.

I am based in Australia and do not drive a car - cycling and taking public transport when possible, otherwise borrow my wife's car. I have a lot of experience in Computational Fluid Dynamics (aka CFD) and have recently gone into doing modelling for cars.

I have personally developed two tools (please google for links as I am not allowed to put links) that may be of use to some of you:

1) Khamsin, a SketchUp Plugin for CFD Modelling: in short it is a CFD modelling environment integrated to SketchUp (a free 3D CAD environment). It uses open-source CFD software for the number crunching. While it has a small licensing fee for commercial use, it is free for non-commercial use;

2) Aerodynamic on Demand: this is a simple web portal to submit CFD analysis to estimate aerodynamic performances.

I hope that any of these may be put to some good use - reducing dependency on fuel is a good thing.


Cd 08-29-2013 04:09 AM

A very, very warm welcome !
Glad to have you here sir .

MetroMPG 08-29-2013 08:56 AM

Welcome, Julien.

Feel free to post the links, minus the 'http' bit -- that'll get it past the filter. I'll edit that part back in for you afterwards. Or you're also welcome to post 4 more times to gain permission to post full links.


Grant-53 08-31-2013 12:34 PM

Welcome aboard, mate! I worked at Testori Interiors which designs interiors for railcars and airliners. My fairings for upright bikes take into consideration taking a bike onboard a bus or train. I have commuted with a bike on a bus and it worked well. The tools of CFD software is a great help in refining designs.

mcrews 08-31-2013 12:52 PM

normally my first advise is to pumpup the psi and get a mpg gauge........!!!!

keep doing what your doing!!:thumbup:

julien.decharentenay 08-31-2013 08:41 PM

Thanks for the warm welcome.

And thanks for the pump-up the tyre advice. I stopped by the service station on my way to my Sunday workout (kayak in the local creek) to pump up the bike tyre. It made a lot of difference in cycling effort... I will check my wife car tyre pressure next.

Happy Father's Day - it is today in Oz, but I am not sure if it falls on the same date in other part of the world.

julien.decharentenay 08-31-2013 08:44 PM

I forgot to mention: I am using Gmail. The registration emails (from webmaster email address) arrived on my Spam folder. It took me a couple of days to notice...

NeilBlanchard 08-31-2013 09:06 PM

I would love to be able to do CFD on my CarBEN EV5. I see it is a plugin for the Windows version - is it tolerant of "leaky" models?

Welcome to EM! I am installing Khamsin now - I hope you don't mind questions!

First question; the Install link for EnSight gives an error: Sorry, and unexpected errr occurred. Message: can't convert nil into String

The Install link for curl and for PuTTY both give a 404 errors. And the OpenFoam Installer also has a 404 error.

julien.decharentenay 09-08-2013 08:54 PM

Hi Neil,

Thanks for the message. Khamsin is only available on the Windows version of SketchUp (I do not have the resources to focus on the Mac version)...

There is no "set in stone" requirement for a watertight geometry when using the openFoam based solver. Khamsin (and the underlying tools) considers sets of faces, not solid volumes. Best to check the analysis to confirm that meshing has only occured in the right places (ie the gaps were not too large that the mesh is also generated in geometry that is not relevant). Let me know how it goes.

Thanks for reporting the error message (honestly, the setting up of the third party is a sticky point in the current version). Below is from what I am considering order of priority:
- OpenFoam: Download and install from
- curl: A copy of curl is shipped with the code in {SKETCHUPINSTALL}\Plugins\Khamsin\Third Party\curl.exe
- PuTTY and EnSight: do you need them? The first one is required if you are planning to send the analysis to a Linux machine or to Amazon AWS. The second one is a commercial post-processing tool. The free version is limited in size of cases and I would advise you to use ParaView (free, but not very easy to use initially).


NeilBlanchard 09-08-2013 10:22 PM

I have to admit that I am stumped with getting started in this - I installed everything that I could get to work, and I have no idea on how to use any of the programs. The plugin seems to do nothing. I have both a Windows and a Mac version of SU; as I am running WinXP in Fusion on my Mac.

Does the CFD analysis run on my machine, or on a server? I am not able to get past go, as it were...

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