World Solar Challenge

[Paul93]

Hello all, I'm a third year mechanical student working as part of a team who are attempting to compete in the World Solar challenge in 2014. We have been working on it for around 6 months now but a lot of that time has been spent recruiting people, theory reading and sorting some admin issues. I have been put in charge of the aerodynamics team and we have recently stated to get down to work. Unfortunately the way our university course works we get exposed to very little aerodynamics and those we do come under the general topic of fluid mechanics. This has meant we have spent time on theory reading to get our knowledge at a suitable level. We have a basic shape and dimensions to work from now but we are a bit of a loss as to where to start in the process of making the shape aerodynamic. I am wary of being over reliant on CFD software and taking the results from it as read. My idea was to look at the 2d profile of the car and calculate the required underside camber for ground effect, and use flat plate assumptions to check if we have laminar flow along along the profile. I wondered if anyone who had any experience of knowledge on aerodynamic development would be able to suggest a more suitable route to follow?

Cheers

[marcush.]

isn´t your Primary Goal to create sufficient solar Panel surface and reduce drag? what would you expect from spending time to create downforce?

looking at 2d profiles does not apply here ,the vehicle will have a very narrow span width compared to ist chord length and along that span several Major obstacles (tyres -human Body packaging constraints )I don´t think a 2d optimisation will give results of any worth -this is entirely 3d .Move to CD-adapco or similar -they released a new package the other day allowing you to directly evaluate your CAD work and Morph it inside the CFD package. As i understand their Software is available for studends for free you only Need some sponsorship to buy calculating resource...
with the Speeds and power available Detail design and manufacture (gaps and Profile correlation to your CAD data) will decide if your drag is good or bad .
WSC is running for some time already and Teams are already in their 4th or 5th Iteration of machine.I think as always it´s a good idea to study all competitors first and Analyse their work and how it evolved over years.

[Greg Locock]

Hi Paul, I was a member of Aurora for a long time. Go and buy "Speed of Light" WSC 1996 technical report in which Clive Humphris describes how we designed our fairly successful cars over the years. Clive is an aero guy first and foremost.

In my experience you do not have enough time to put a good debugged entry together, unless you have all the major components on order now.

As you both suggest, biasing the camber line of the airfoil to account for ground effect and hence generate zero downforce is the name of the game. If you get it wrong you can adjust the flying height and pitch to trim the thing. That takes time but is worth the effort.

You won't get laminar much past 40% unless you have some amazing bodywork, we got laminar to 60 on a glass fibre plug, but once you add cells, even with a gel coat, no chance.

Incidentally don't worry about Cd as such, it is all about surface friction (ie assume 100% inertia recovery)

[vishalg]

Students from Canada design a solar car to participate in a grueling 3,000-kilometer timed race. Check out now...
http://www.ansys.com/staticassets/ANSYS ... -V8-I1.pdf

[Greg Locock]

They came 8th out of 10 in their class.

Very faint sound of applause

With an average speed (65 kph) slower than was set 27 years ago.

OK, I know they were 'only students' but there is a huge amount of literature out there on how to design and build cars, for heavens sake in 2007 we fitted modern cells and a wheel motor to a 1987 car and averaged better than 70 kph.