The difference between buffeting and turbulence - Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums
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post #1 of 16 Old 10-30-2006, 09:59 PM Thread Starter
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The difference between buffeting and turbulence

A while ago we were discussing buffeting and what was expected when we finally found a good windshield. I thought I had my setup pretty well dialed in as good as it will get. Well, I was wrong. On the way home tonight, I was going about 80 km/h and for some reason I decided to stand up on the pegs. When I stood up I found myself in a nearly silent, smooth, slipstream of air like I've never experienced sitting down. It was amazing. So amazing that I sat down and stood right back up again.

Now, when I'm sitting on the seat, I don't feel any buffeting, i.e. tugging/slapping of air on the helmet. But I sure do hear a lot of wind noise from the turbulence. So, much so that I thought I had bought a crappy noisy helmet. Ducking down or raising myself up changes the noise level but the it never approaches the quiet I experienced standing up.

So, now I have to resume my quest for a good windshield.

Rob

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post #2 of 16 Old 10-30-2006, 10:16 PM
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When you are standing up you are in a smooth laminar air layer. The only way to achieve this effect when behind a windscreen is if the screen is so lopw that the disturbed air flow is hitting you at chest level. On the Strom that means either no wind screen, or at least a very low one, and change the position of the mirrors futher out and lower.

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post #3 of 16 Old 10-31-2006, 12:53 AM
 
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The difference between buffeting and turbulence.....


IMHO, the difference is whether you take two Ibuprofen or four!

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post #4 of 16 Old 10-31-2006, 11:27 PM
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Unattributable Quote

When I was going to night school taking a class in Transport Phenomena (Fluid Mechanics and Heat Transfer, not busses and trains), we got a quote one day on the board, but I can't recall who'd said it or exactly how it went:

"One day when I pass and meet the creator I will have two questions. First, Why Relativity? Second, Why Turbulence? I bet I will get an acceptable answer for the former."
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post #5 of 16 Old 11-01-2006, 10:13 AM
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Yep

Same thing happened to me. Which is what prompted me to remove my stock windshield and ride without it. Completely different bike. I then cut the stock screen down to 1/2" above the dash mounts and it's incredible. Clean air, right to my helmet. Helps not only with buffetting, but also keep fresh air in my helmet vents!

Buffetting = Crappy airflow from a windshield that is too far away and no venting to reduce vacuum - fixable with shorter, vented screen

Turbulence = Bad air coming off of trucks, SUV's, etc... Nothing we can do about that!!

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post #6 of 16 Old 11-01-2006, 12:58 PM
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Quote:
Originally Posted by IndianRider View Post
im confused .. this seems to be contradicting the fact that many v-strom riders actually "raise" their shield and/or install a TALLER and sometimes wider shield to minimize the buffeting ..

anybody got some more input or explanation to the opposing theories ?
Sure, they're not really opposing at all. Mostly they're oversimplifications of the same impossibly complex fluid dynamics equasion.

When you put something in an air stream, in this case a windsheild, the air has to flow around it. For illustrative purposes, let's think in one dimension and imagine it as a rock in a stream.

Downstream of our windsheild rock, there's a teardrop or triangular area where the water is calm and makes a very slow swirl. In a stream it's called an eddy, in a windsheild usually a slipsteam.

The difference between the high/big sheild and low/no sheild theorys is in where they're putting your head, relative to that slipstream. Back to our rock, if it's a little bitty rock, there's only a small area of calm water. If you look at the water off to the side of the rock, there's still a strong current, but the current is smooth and steady. That's where your head would be in the low/no scenario.

If the rock is a big honking rock, there's a big honking calm area behind it. That's what the big sheild is trying to create, and where your head tries to be in a high/big scenario. The problem with acheiving that big calm area is that a motorcycle sheild isn't just a rock hovering in midair we can sit behind.

Imagine we've got our rock, be it big or small. Now, imagine we plunk something, say another rock or a knee or a motorcycle mirror, in the water right near our rock. Now there's two slipsteams, but they're interfering with each other. A simpler way to think about it is that every extra thing we put in the stream near our windsheild rock is changing the way the stream around the rock behaves, not always in a desirable or easily predictable way.

The result is that if someone doesn't mind the steady solid stream of air, they'll be pretty happy with the low/no route, as it's much much easer to keep the air clean, since their head's not near anything that can cause weirdness. If they want calm air, rather than steady air, they need to go the big/high route, but because of all the motorcycle and person interfering with the air stream, it takes some work to get the air clean.

There's other partial solutions, but I've already written a book, so there's the basic idea.

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post #7 of 16 Old 11-01-2006, 11:30 PM Thread Starter
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Good explantion RMRR.

I laready have a pretty cut down shield but the noise level is very high. I may try ditching the shield tomorrow and see what that's like. Stay tuned...

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post #8 of 16 Old 11-02-2006, 11:17 AM
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aircav - you'll FREAK at how smooth it is without the shield. If I could get over the looks of it, I'd ride like that all the time.

Noise?

EARPLUGS!! What noise?

I wear foam plugs, or noise-cancelling earbuds with my MP3 player. No noise here!!

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post #9 of 16 Old 11-05-2006, 12:58 PM
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MP cycle designs tall screen with Saeng micro edging, no turbulence or buffeting unlees in real disturbed air (behind large vehicles) and quiet as my ST1300.
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post #10 of 16 Old 11-05-2006, 06:32 PM
 
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For whatever it's worth, I've gone back to my OE wind screen. I do have the Madstad unit installed, but I'm enjoying the bike more with a smaller screen. I'd say it even looks better, but V-Strom owners don't care about appearance
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