01-20-2013, 02:31 AM | #29 | |
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What we want is the ability to transfer high pressure under the car to above. What a diffuser does is speed up the air going under the car in the front, then slows the air down as it tapers up in the back, but in the back is a big low pressure section. So the pressure difference also 'pulls' the higher pressure under-car air to 'fill' the low pressure behind it. The reduction of high pressure under the car reduces lift, and the reduction of low pressure behind reduces drag.
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01-20-2013, 02:41 AM | #30 | |
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Were there any changes through S2k models that could account for the differences?
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01-20-2013, 04:08 AM | #31 | |
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01-20-2013, 04:10 AM | #32 |
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01-20-2013, 05:19 AM | #33 |
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nice
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01-20-2013, 05:26 AM | #34 |
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I'm just gonna put this out there...that rear diffuser wing thing is actually just for looks. The leading edge is almost flat, it breaks up any of the potential of the rest of the "diffuser" by blocking airflow rather than guiding it. I have it on my car and love the look but it's function is purely cosmetic.
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01-20-2013, 02:47 PM | #36 |
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Diffusers and under body panels are cool because they're one of the few mods/designs that can simultaneously reduce lift (or create down force) and reduce drag. By giving the air under the car a clean path and smooth exit, the pressure differential caused by the shape of the car can be reduced. Depending on the car, it could be negative. Not likely with the bubbly roof line of our cars.
Overall these cars are pretty solid aerodynamically compared to many others, but the traditional coupe shape isn't as inherently down force friendly as something like a McLaren 12C or other wedge like supercar. |
01-20-2013, 09:42 PM | #37 |
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So in the spirit of DIY, has anyone done seen the guys at Ecomodder and their "tuft testing"?
LINK to AutoSpeed Similar to the wind tunnel tests summarized above, it's a really simple way to visualize flow directions and turbulent spots. Painter's tape + yarn/string + video camera = data. From there, I'm sure we could pinpoint the easiest gains. Alternatively, I know that we could develop a solid model and run a CFD analysis to get those beautiful clown puke pictures... but at this point, tuft testing is much more accessible to the DIY community. If someone wants to volunteer for CFD duty, I'd be glad to help, but it's beyond my experience. |
01-20-2013, 10:07 PM | #38 | |
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Another is paint streaks, where a series of dots are painted on the car which then makes a few runs, they then look at the trails left on the car. Analysts still use a similar technique when they can get pictures of race cars that run in wet conditions. They have very distinct streamlines left on them. They are particularly useful for analyzing inlet effectiveness.
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01-20-2013, 10:19 PM | #39 |
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Does anyone have more pictures of the TRD Griffon underbody work? I'd like to try and replicate their work since it's probably the most extensively tested stuff for our cars so far.
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01-20-2013, 10:29 PM | #40 |
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@serialk11r Don't know if you've seen this thread. Thought you might be interested.
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01-20-2013, 11:31 PM | #41 | |
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I still prefer string since you can see flow separation more easily. For a given frontal cross-section (assuming it's unavoidable and constant), we can lower the drag force on the car by keeping the flow laminar and connected. Good opportunities for drag reduction:
Wheels will generate turbulence around them, for alot of reasons (too many to name). It's usually best to guide the airflow away from them to avoid unnecessary drag. Obviously race cars will have dedicated ducts to sent air to the brakes, and that's a different ballgame. The rest of them are about maintaining laminar flow as much as possible. The body panels will never resemble an airfoil/teardrop, but similar concepts are still relevant. Flow should stay connected with the body panels, and body panels should never create pockets. Side note: I realize the golf-balling a car is somewhat legit science, but good aero can generally trump bad aero+dimples. Use turbulence only when necessary. |
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01-20-2013, 11:50 PM | #42 | |
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Higher air speed = lower pressure = less lift/more downforce What are the effects of lowering the car in terms of lift/downforce? |
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