[KVRC] Khamsin Virtual Racecar Challenge 2016

Post here information about your own engineering projects, including but not limited to building your own car or designing a virtual car through CAD.
User avatar
machin
162
Joined: 25 Nov 2008, 14:45

Re: Khamsin Virtual Racecar Challenge 2016

Post

I just extended the sidepod down from the step until it reached the lowest permissable floor height and then extruded a flat floor over the the area I wanted in front of the sidepod.

I presumed that area at the back of the sidepod was just to enclose the suspension so I've filled it in with the diffuser.

There's nothing innovative about my bodykit so if I get time I'll post some pictures over the weekend. I plan to fully disclose the details of my design throughout the season and pick out the places where it doesn't work, a bit like we did with your car at the end of last season.
COMPETITION CAR ENGINEERING -Home of VIRTUAL STOPWATCH

User avatar
RicME85
52
Joined: 09 Feb 2012, 13:11
Location: Derby

Re: Khamsin Virtual Racecar Challenge 2016

Post

I looked at doing that with the sidepod but it didn't fit right with the curves.

User avatar
CAEdevice
49
Joined: 09 Jan 2014, 15:33
Location: Erba, Italy

Re: Khamsin Virtual Racecar Challenge 2016

Post

Hi, here is the intro class with that volume filled, maybe it could help your modeling.

https://dl.dropboxusercontent.com/u/522 ... filled.zip

User avatar
RicME85
52
Joined: 09 Feb 2012, 13:11
Location: Derby

Re: Khamsin Virtual Racecar Challenge 2016

Post

Matteo Image
Thats excellent, a big help, thanks.

User avatar
CAEdevice
49
Joined: 09 Jan 2014, 15:33
Location: Erba, Italy

Re: Khamsin Virtual Racecar Challenge 2016

Post

RicME85 wrote:Matteo http://www.otf2.com/forums/images/smili ... bR2Dbe.gif
Thats excellent, a big help, thanks.
If you need help with CAD, just let me know :)
My job has to do with CAD half of time... if I'm at office it is not a problem to help.

User avatar
RicME85
52
Joined: 09 Feb 2012, 13:11
Location: Derby

Re: Khamsin Virtual Racecar Challenge 2016

Post

Should be fine now thanks, just couldnt get my head around filling in that section with the curves in Sketchup.

julien.decharentenay
julien.decharentenay
10
Joined: 02 Jun 2012, 12:31

Re: Khamsin Virtual Racecar Challenge 2016

Post

machin wrote:3m^3/sec is the total, so if you split it equally left and right that is 1.5 each side.
Sorry I was off trying to sort out OCCFD parallel issues. I confirm that the 3m3/s is total.

julien.decharentenay
julien.decharentenay
10
Joined: 02 Jun 2012, 12:31

Re: Khamsin Virtual Racecar Challenge 2016

Post

CAEdevice wrote:I was wondering if the bc applied to the inlet/outlet cooling surfaces are a flow (larger surface means lower air speed) or a velocity.
The bc applied to the inlet/outlet cooling surface is a velocity condition. OCCFD calculates the STL area and normal and uses this to specify the velocity.
@AlonsoFan: I can't read the text in your image, but I would try with Paraview 3.9.8(.1).
In all likelyhood this has to do with OCCFD issues with running openfoam from cfdsupport in parallel. ParaView will only be used after the second simulation is complete.

julien.decharentenay
julien.decharentenay
10
Joined: 02 Jun 2012, 12:31

Re: Khamsin Virtual Racecar Challenge 2016

Post

Hi, Sorry for the late responses. I have (am still) trying my best to get through the issues. I have updated OCCFD to have a better recognition of the openFoam distribution being used. There are teething issues with the cfd support distribution - sorry to have them so close to the first race.

The main issue at this stage seems to be:
1) Parallel running: The new patch (007) http://www.khamsinvirtualracecarchallen ... .1-007.zip has been updated to identify the openFoam distribution based on path location and using a logic based on the identified openFoam distribution.

If using openFoam from cfdsupport: Please install HPC MS-MPI from https://www.microsoft.com/en-us/downloa ... x?id=36045 with the default installation directory (ie C:\Program Files\Microsoft HPC Pack 2012 ). Ideally you might want to remove openMPI prior to installing MS-MPI.

As an alternative, there is now an option for forcing OCCFD to run on single processor... So at least there is a way around that does not involve cygwin, etc.

2) Meshing: The mesh is generated using snappyHexMesh. In some cases (usually non watertight geometry), the inside of the car may be meshed. When this happens, it is likely to have the following symptoms: divergences (usually the inside mesh will have a worst mesh quality than the outside and more prone to corners doing strange things) and wrong results (the inside mesh will have some level of pressure that will act on the shell to affect drag and downforce). There are two markers: the mesh size that should be around 4,5 millions cells normally and goes up to around 6 millions cells with the inside mesh and the force distributions that look strange. When this happens, the easier solution is to use a tool to close the holes (I personally use netfabb, but other tools can be used - see mesh cleaning steps in this blog post http://blog.othermachine.co/convert-stl-to-step)

Last but not least, please note that the Very Stable option has been moved to be the default option.

User avatar
CAEdevice
49
Joined: 09 Jan 2014, 15:33
Location: Erba, Italy

Re: Khamsin Virtual Racecar Challenge 2016

Post

Thank you Julien. Using the very stable solution as default is a good idea.

User avatar
RicME85
52
Joined: 09 Feb 2012, 13:11
Location: Derby

Re: Khamsin Virtual Racecar Challenge 2016

Post

I now have a completed car! Not the prettiest nor my best work but it is a starting point.
Need to reinstall my PC OS and get OCCFD set up and see if I can get some data yo compare to last years final iteration.
Thanks again Matteo for doing that mod to the sidepod, helped a lot. If anyone else is going to use that file, it is worth noting there is a slight issue with the rear wheel well, it needs tidying up slightly as it encroaches on the wheel.

User avatar
variante
138
Joined: 09 Apr 2012, 11:36
Location: Monza

Re: Khamsin Virtual Racecar Challenge 2016

Post

Well done, Ric. Hopefully we're going to have a good number of competitors from the first to the last race.

On my side, I'd say that my car is decently developed, but not necessarily competitive enough to win...i'm struggling with time more than ever :(
One thing I can anticipate about my car is that it is an evolution of last year's, despite my efforts to produce a whole new body layout. Luckily, i managed to develope it with OCCFD (last year version, for the moment), so i shouldn't have the balance problems that i experienced during the first three races of 2015.

User avatar
Alonso Fan
10
Joined: 06 Apr 2013, 18:21

Re: Khamsin Virtual Racecar Challenge 2016

Post

julien.decharentenay wrote:Hi, Sorry for the late responses. I have (am still) trying my best to get through the issues. I have updated OCCFD to have a better recognition of the openFoam distribution being used. There are teething issues with the cfd support distribution - sorry to have them so close to the first race.

The main issue at this stage seems to be:
1) Parallel running: The new patch (007) http://www.khamsinvirtualracecarchallen ... .1-007.zip has been updated to identify the openFoam distribution based on path location and using a logic based on the identified openFoam distribution.

If using openFoam from cfdsupport: Please install HPC MS-MPI from https://www.microsoft.com/en-us/downloa ... x?id=36045 with the default installation directory (ie C:\Program Files\Microsoft HPC Pack 2012 ). Ideally you might want to remove openMPI prior to installing MS-MPI.

As an alternative, there is now an option for forcing OCCFD to run on single processor... So at least there is a way around that does not involve cygwin, etc.

2) Meshing: The mesh is generated using snappyHexMesh. In some cases (usually non watertight geometry), the inside of the car may be meshed. When this happens, it is likely to have the following symptoms: divergences (usually the inside mesh will have a worst mesh quality than the outside and more prone to corners doing strange things) and wrong results (the inside mesh will have some level of pressure that will act on the shell to affect drag and downforce). There are two markers: the mesh size that should be around 4,5 millions cells normally and goes up to around 6 millions cells with the inside mesh and the force distributions that look strange. When this happens, the easier solution is to use a tool to close the holes (I personally use netfabb, but other tools can be used - see mesh cleaning steps in this blog post http://blog.othermachine.co/convert-stl-to-step)

Last but not least, please note that the Very Stable option has been moved to be the default option.


That's great news! Thanks for your effort. I will be attempting another analysis as soon as I complete my university coursework :)
SHR Modding
Youtube
Twitter
Discord

Sound Developer for Reiza Studios
Sound Modder for Assetto Corsa

etsmc
etsmc
7
Joined: 04 Apr 2012, 13:20

Re: Khamsin Virtual Racecar Challenge 2016

Post

a little update on my testing with OCCFD
what I have installed is OpenFOAM for windows version 16.02 which is OpenFOAM 2.3 and was using OCCFD 1.1-006, I had an issue with divergence on the local test but I think that may have been a hole in the mesh as Julien pointed out. on the very stable test, i was running fine for 48hrs until my machine decided to reboot.

I am now trying it on the 007 build with a newly exported STL file (didn't know about netfabb so will look into that) and hopefully, my machine doesn't reboot.

specs wise it an old machine which is why it is slow. old dual core processor and only 4gb of memory.

julien.decharentenay
julien.decharentenay
10
Joined: 02 Jun 2012, 12:31

Re: Khamsin Virtual Racecar Challenge 2016

Post

@etsmc You may want to use the light version of OCCFD for part of the development. Expect to see some differences (in particular in regards to downforce), but you should be able to have a faster turn-around (and get confirmation that OCCFD is working from start to finish),