Quote:
Originally Posted by aerohead
*Same for Mythbusters.They must be an embarrassment to whoever authorized an engineering diploma.
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Not sure why everyone keeps bringing up Mythbusters, at no point have I referenced them
I don't even have cable television
Quote:
Originally Posted by aerohead
*There is only an inch or so of laminar boundary layer on a car.The rest is turbulent boundary layer.
*This TBL allows for attached flow as long as the body cross-section does not vary by much (area rule/sectional density).
*Once you have TBL there is no need of dimples,as they'd be superfluous and only increase drag.
*If you have contours on the car which are too 'fast',then a dimple might behave as a crude VG,but they are in no way as efficient as a true VG,as far as feeding momentum into a compromised TBL which is otherwise separating.
*It is the vortices created by VGs which feed momentum into the weak TBL,forestalling separation.
*Dimples cannot produce the quality of vortices as with VGs.They are very inefficient in this regard.
*The only reason golf balls have dimples instead of VGs is because the ball spins,and regardless of the balls orientation in the air,the dimples always present the same 'face' to the boundary layer,allowing predictable flight.
*If the ball could be oriented and struck with the driver or iron without imparting spin,then we could put VGs on them and extend a drive or chip shot.
*In water,the dimples would help the board or hull 'plane',as in a stepped hull.The curvature is too gentle to produce separation.
*I feel like Bez has not read Hucho or anyone else,and is clueless about boundary layer theory,otherwise he wouldn't have done what he's done.
*Same for Mythbusters.They must be an embarrassment to whoever authorized an engineering diploma.
*If any notchback car is going to be modified for boundary layer control,it should be done with VGs.It's just better science.
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I understand that the TBL shouldn't need to be energized on streamlined surfaces to stay attached, but why are there studies and wind tunnel experiments that show a decrease in surface friction and an improvement of .cd values on already streamlined surfaces (passenger train cars for example, they have no curves or bluff characteristics along their sides). According to your statements, there shouldn't be any improvement upon an already perfect TBL/BL scenario via the use of dimples or any other such "fake vortex generator"?? I guess I'm just confused by the fact that everyone says it won't work, yet I'm the only one providing data/links to anything. So while vortex generators might be "better science", is that true because people simply won't look at new data that didn't exist when Hucho did all of his stuff? Or is it because these new studies are incorrect, or maybe they aren't actually as efficient as they would be if they used "real" vortex generators?
"As the layers of air move over a rough surface, the air particles in the layer closest to the surface collide with the surface. This makes the air particles slow right down (and right at the surface, they completely stop!). These particles then collide with air in layers a bit further out and make them slow down as well. As you move further away from the surface, the speed of the air particles is not affected.
This boundary layer is laminar at the beginning of the flow, but it gets thicker as the air moves along the surface and becomes turbulent after a point."
So even on a super slippery, super streamlined surface, eventually friction/drag increases and separation occurs right? Vortex generators are used to mix things up and change the dynamic of this occurrence correct? And more often than not, they focus entirely on a point where separation will naturally occur right? Or on the leading edge of something at an attack angle. You wouldn't just put them down the length of the car, or all over the top of the car for no reason. The research I have been linking to, says it decreases surface friction and thus prevents the friction from increasing and the occurrence of separation (to some extent)... Which is similar but different from what Vortex generators do. I don't claim to know how, which is why I'm providing quotes, links, and statements from other places.
If I would have known it was such a hot button topic, and that I would need to look so much stuff up just to not seem like an idiot who watched some TV episode, I wouldn't have bothered posting in the first place
Anywho, I guess it's not a big deal, I sure don't have the means to test any of it... So I guess I'll move on to something else
~C