Cambridge's Resolution - Aerodynamic teardrop solar car

[youtube]_uMB2Va635A[/youtube]

Pretty clever design, in my opinion. It uses the teardrop shape, which is the most efficient shape in the world, while using solar tracking inside the teardrop to maximize solar power.

http://www.worldsolarchallenge.org/team_info/overview

Apparently the countdown for the race is 20 days from now. Can't wait!



Look at the effective frontal area on that perfect prone streamliner! That's like almost a 100x improvement over a regular bike! Now only if there was a way to integrate that design into a *relatively* practical vehicle. (Not like 4-person + groceries kind of practical, more like, 1 person and can comfortably travel over 1000+ miles at 60mph on regular highways kind of practical, possibly with a bag of groceries.)



Look at the drag coefficient on the streamlined body! Yowza! Notice that a fish, an animal with the greatest fluid dynamic efficiency demands in the world, is shaped just like a streamlined body.

[Btw, for those who don't understand the importance of aero, aerodynamics is extremely important for range and speed. If you could take your average electric bike with battery panniers hanging off the side and somehow transform it into the most efficient shape in the world, you could possibly increase range by upto a factor of 100x. That is, an ordinary 25 mile range becomes a 2500 mile range. If batteries are limited in range, than aero is a possible solution.]

This seems leaps ahead, yet still I see room for improvement.


edit: Looking at the bottom pic you just added, there looks to be something wrong. Look at the sphere the half sphere and the teardrop shape. Something don't quite gel, as can be seen from the long and short cylinder. The half sphere shouldn't be lower than the full one should it?

friendly1uk said:

This seems leaps ahead, yet still I see room for improvement.

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Yep, definitely could be improved. Incremental design improvements are the steps engineering takes in the pursuit of perfection.

However, the idea this team has thought up is definitely revolutionary over existing paradigms, in a good way. Clever, clever, clever.

Rotating, tracking solar panels inside a translucent teardrop vehicle - man, that seems ingenious. I was thinking about the solar tracking aero problem (How do you track the sun without destroying aero?) and this is definitely a neat solution.

I think everyone else is competing for second place now.

It is all about cell positioning. They have a real advantage there. I hope the canopy holds out for them, as I'm thinking a borosilicate cold glass or something brittle like that

edit: Stop editing, I keep repeating you lol

friendly1uk said:

edit: Looking at the bottom pic you just added, there looks to be something wrong. Look at the sphere the half sphere and the teardrop shape. Something don't quite gel, as can be seen from the long and short cylinder. The half sphere shouldn't be lower than the full one should it?

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Looks like other sources online support it. Could be that aerodynamics isn't all that intuitive, and optimization, after choosing a basic shape, is best left to simulation and experimentation.

Good thing experimentation has already determined the 'teardrop shape' is among the most aerodynamic volume-containing shapes in the world. (The most aerodynamic is actually a line (Like an arrow), but you can't stuff a human inside one of those, lol.)

I'm going to build another wind tunnel one day and check lol

I should really of given that last post more thought.

they mentioned moveable tracking cells have not been used in solar cars, it has been many times.

friendly1uk said:

........Looking at the bottom pic you just added, there looks to be something wrong. Look at the sphere the half sphere and the teardrop shape. Something don't quite gel, as can be seen from the long and short cylinder. The half sphere shouldn't be lower than the full one should it?

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Spheres cause more drag then one might think. (With the exception of Endless-Shpere of course. :lol



It is why golf balls have dimples.

I have to admit, looking at the Cd chart, it seems a bit bizarre how a sphere has a Cd of .47 while what looks to be a sphere except stretched out towards a point on one side has a Cd of .04. It's funny to think the 'stretched out' part could improve the Cd by more than a factor of 10x.

Looking at the above image, it appears that the stretched out part displaces the 'low pressure region' that the sphere creates, and I'm assuming the difference between the high pressure and low pressure region is largely what creates drag? So, get rid of the low pressure regions, get rid of (most) drag.

I wonder if filling the low pressure region with air while traveling would reduce drag? Not exactly sure how you'd do that, but hypothetically speaking.

swbluto said:

I have to admit, looking at the Cd chart, it seems a bit bizarre how a sphere has a Cd of .47 while what looks to be a sphere except stretched out towards a point on one side has a Cd of .04. It's funny to think the 'stretched out' part could improve the Cd by more than a factor of 10x.

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It makes perfect sense if you know where drag acts on a sphere.

Chalo said:

swbluto said:

I have to admit, looking at the Cd chart, it seems a bit bizarre how a sphere has a Cd of .47 while what looks to be a sphere except stretched out towards a point on one side has a Cd of .04. It's funny to think the 'stretched out' part could improve the Cd by more than a factor of 10x.

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It makes perfect sense if you know where drag acts on a sphere.

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I'm getting this kind of force diagram for the aero.



So, it seems that the stretched out part prevents the formation of the low pressure region, thereby minimizing the difference in the horizontal force vectors and, thus, the net force vector called 'drag'.

It doesn't seem intuitive how a 'small change' could make such a big difference, but it's interesting to see how the actual physics works out.

With my thermodynamic education, anytime I imagine "high pressure", I imagine a high-density of air molecules while "low pressure" entails a low density (Assuming the same temperature). So the low pressure region causes a smaller force vector because there's fewer molecules in the area directly behind it to bounce around and hit the back of the sphere.

(Edit: I should've made the vertical arrows bigger. I doubt the difference in the left arrow and vertical arrow is going to be that big at 20-30mph... maybe 1000+ mph...)

It is hard to look at a sphere photo in 2d. Both sphere and semi set up a high and low pressure area side by side that wants to cancel out. The difference between the two is so great that air movements are quite strong. The high pressure areas need fill the low pressure area is enough to try and change some of the airs direction through 180 degree's, and sets up conveyor currants within the low pressure area. It is very turbulent. The drawn out shape never see's such a great pressure differencial at any point as it slowly tapers off. Flow can keep going in the same direction almost. The long shape controlling the speed at which the air can get back to where it started ahead of the object. The air stays laminar rather than swirling. The gradual taper allowing the air back in to place progressively in a controlled manner.

Semi v sphere is not so simple. That trailing portion of the sphere is no use as a vane, but offers some interference to the air that wants to swirl back to the void. Stopping the longer converyor currants from forming. This lack of established routes to follow complicates things, making the air do more work to get back where it wants to be.


Now that is the post I should of made before. Still not actually looked anything up though. I like to make physics up as I go along lol. It had my physics teacher come to see my mum, to say I'm a natural and should actually do something in class. Which I take as quite a compliment. It was just all so obvious though. Unlike this sphere business


You can make a wind tunnel with drinking straws. I crammed them in to a 100mm duct, using a pond fogger to see what went on. It seemed to work, but it was not the goal. We were just messing about. The project was reducing noise in an extract system by straightening up the air after the systems intake fan. It was ok, but acoustic dampeners more like a car silencer have the edge where size is not so important.

swbluto said:

I wonder if filling the low pressure region with air while traveling would reduce drag? Not exactly sure how you'd do that, but hypothetically speaking.

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Dimple it, like a golf ball.......

[youtube]LvVuuaqCC7A[/youtube]

e-beach said:

swbluto said:

I wonder if filling the low pressure region with air while traveling would reduce drag? Not exactly sure how you'd do that, but hypothetically speaking.

Click to expand...

Dimple it, like a golf ball.......

[youtube]LvVuuaqCC7A[/youtube]

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lol.

I read mpg can be improved somewhere in the 10-20% region by putting a dimple pattern on a car.
,
Makes me wonder what kind of Cd might be achievable by dimpling a streamlined body.

Now, that idea is starting to remind me of fish. The surface of a fish isn't perfectly smooth, it has overlapping scales. Does that play a role in improving hydrodynamic efficiency? Curiously, birds also have the same kind of imbricating surface, except implemented with overlapping feathers instead of overlapping scales.

Maybe that's why birds are preening themselves so much? They're improving their flight characteristics.

The size of the average feather compared to the size of the average scale seems like it might be proportional to the ratio between the molecular density of water and the molecular density of air (Molecules/cm^3). I wonder if that's the case, and if so, what the operating mechanism might be?

Something tells me nature figured it out before we did, lol.

swbluto said:

Something tells me nature figured it out before we did, lol.

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http://www.the-scientist.com/?articles.view/articleNo/24272/title/Mercedes-and-the-boxfish/

Mercedes and the Boxfish

In 1996, Dieter Gürtler and his colleagues from the Mercedes Technology Center in Sindelfingen, Germany, were looking for a model for a holistically conceived bionic car, respecting at once physics, design, and aerodynamics. So he turned to Ronald Fricke, head of the ichthyology department at the Rosenstein Museum in Stuttgart, with its huge collection of preserved fish.

They were "thinking about a bionic car and ? fish models for it," Fricke recalls. The team's first instincts were to use streamlined sharks, penguins, dolphins, and tunas. But on a visit to the museum, it became clear that their "ideas of tunas and sharks were not useful to design cars, which contain a cubicle for passengers, while swiftly-swimming fishes are compressed," Fricke says. "It was our idea to choose a slowly but steadily swimming fish, and the boxfish was the first option."

The boxfish, found in coral reefs, has great structural strength but low mass. Despite the ungainly appearance of the fish, it also has extremely low flow resistance, with a drag coefficient of an incredible 0.06. For comparison, a penguin flying through water is considered extremely aerodynamic with a coefficient of 0.19. More streamlined, lower-drag fish do exist, but they are not as rigid or maneuverable as the boxfish, nor do they have a relatively huge cross section.

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http://www.gizmag.com/bumpy-whale-fins-set-to-spark-a-revolution-in-aerodynamics/9020/

Bumpy whale fins set to spark a revolution in aerodynamics

March 21, 2008 It seems despite man's endless ingenuity and the incredible modeling power available to inventors through CAD systems, we keep looking to nature to find ever more effective ways of doing things. Millions of years of evolution's trial and error approach have resulted in some incredibly effective designs that are ready to be incorporated into human constructions if we can only identify, understand and replicate them. The random-looking bumps on the humpback whale's flippers have just inspired a breakthrough in aerodynamic design that seems likely to dramatically increase the efficiency and performance of wind turbines, fans, flippers and even wings and airfoils. WhalePower's tubercle technology seems like nothing less than a revolution in fluid dynamics.

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Interesting reads. Reading something like "The vortices generated help provide propulsion", which presumably helps negate the drag, makes me realize it's a lot more complex than low pressure vs. high pressure, lol.

Features like that for use on car bodies sounds like something that's probably best discovered and optimized by randomness, assuming accurate simulation algorithms exist. Finding the best surface pattern by human design seems... computationally infeasible, though I'm guessing human design could probably get close to the global optimum.

(Jeez, seeing the utility of mimicking the natural process of evolution and randomness to come up with better novel designs via simulation, I'm almost convinced that nature is really a big simulation itself.)

Seems the BMW owners know how to make their cars more aerodynamic. (They kind of botched the job a little at :23 with the broken windows, but at least they are trying)

(Wait, is that a 3-wheeler going by at 2:27 in the background? Wtf? Germany has those but America doesn't?? I want to live in Germany!!!)

[youtube]1c7FzXygCG0[/youtube]

swbluto said:

Seems the BMW owners know how to make their cars more aerodynamic. (They kind of botched the job a little at :23 with the broken windows, but at least they are trying)

(Wait, is that a 3-wheeler going by at 2:27 in the background? Wtf? Germany has those but America doesn't?? I want to live in Germany!!!)

[youtube]1c7FzXygCG0[/youtube]

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The guy in the blue shirt is clearly NOT Paul Bunyan.....and what is that pedal car looking thing going across the cross walk at 2:27?

e-beach said:

and what is that pedal car looking thing going across the cross walk at 2:27?

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That's what I want to know! Seeing how a random video has that kind of vehicle going by and I never see anything of that sort in America, something tells me there's a lot of innovation/diversity in Germany.

Bike taxi, I saw a lot of them in Amsterdam.
[youtube]eWkhosR_UWs[/youtube]

That has electric assist, can you hear it? You can see the throttle at his right hand too.

Great application of EV power.

http://www.worldsolarchallenge.org/files/492_final_results_sunday_challenger_class.pdf

Looks like Team Cambridge withdrew. Wonder what happened?

It appears they are competing in the same category as these things...



...So that might have something to do with it.

e-beach said:

Mercedes and the Boxfish

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Apparently, it wasn't complete waste and MB did use some of these findings:

Appears to be a bit unstable.

http://www.theregister.co.uk/2013/10/05/cambridge_withdraws_from_world_solar_challenge/

This 4-seater finished the race.

http://www.solarracing.org/2013/07/04/solar-team-eindhoven-reveals-their-car-stella/