Crap I had a really really great reply then closed the tab instead of the one next to it so I have to reconstruct it. I forgot my golden rule: always highlight and copy posts every few seconds. Poop. Okay reconstruction time.
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So 1st observation is on the Mig... which is kind of driving your thought I guess. The change in the surface to affect an airflow change to stop/start stuff going into the engines does not necessarly mean that it had a macro affect on airflow characteristics. I am not claiming it didn't... or did... just that the conclusion cannot be drawn. These same aerodynamic changes elsewhere on the Mig, or on a car for that matter, may or may not have produced any measurable change. Again, not claiming did or didn't, just insufficient data.
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My first reply was stunningly great. Ah, I hate reconstructing documents.
All I know is that Belyakov reported that was the reason for the failures "vortexes caused by the coating of the aircraft dictated removal of certain aerodynamic enhancements as well as physical modifications to the intake system".
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OK, so just a mention of what I have been thinking about... simply add an electric fan or two or more with the appropriate shrouding to positively alter the airflow at the bad portions of the flow "AND" provide some base force thrust as well... like put a couple of the HW750 RC jet fans and get up to about 30 lbs of thrust (think how long your glides would be when 30 lbs is shaved off the overall force drag).... AND, AND (this is the part I am wondering about)... the force thrust is produced from air flow that positively alters the external Cd. as well... but I might be hoping for too much.. appreciate your thoughts here cuz a few people think I am nutz :-)
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The Brabham BT46 was a Formula One racing car in 1978. The cars were powered by a flat-12 Alfa Romeo engine. The original 'A' model had "flat panel" heat dispersing units for getting rid of the heat from the oil and engine coolant. Didn't work. So, for the Swiss Grand Prix the Brabham team rolled out, tada the
fan car. A very powerful fan was mounted in the car that sucked air from under it creating an additional amazing 1,000 pounds or so (that's what the rumor is, anyways) of additional lift. The car raced in exactly one race, whipped everyone and was then withdrawn from the tour.
So, my friend you may take it one step further. Take a large duct, mount the opening to it intersects the entirety of the vehicle and accelerate the air through the duct out the back of the vehicle. You could use a passive venturi effect to do this and cool the air at the same time. Simple. (see my Webernator)
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So friction drag is not because the fluid is sliding across the surface, but because the moving surface is grabbing on to the closest layer and causing the fluid to slide across itself. So any change in surface must "alter" aerodynamic flow to have any effect... ie. big enough to introduce turbulent into streamlined flow, or separated into turbulent flow.... but since both of these are bad with the primary effect, one must ensure the gain is comparable elsewhere. Again, back to vortex generators.
>>Conventional wisdom says that the smoother the surface
>>the better the vehicle slips through the air (closing of gaps, removal of >>wipers, etc.).
Agreed, but I think you really mean "smoother the shape".
>>In the same vein, an introduction of a surface with less surface
>>area would produce less wind resistance.
The former does not lead to this conclusion, however, and I can't figure out how the math does either. Intuitively it does make sense I agree... but I don't see how it maps to any of the equations... but I am not expert here so let me know what I am missing. It certainly does seem to me that less sufrace area leads to less fluid friction and thus to less engergy dissipation, but the fluid force equation on a body doesn't take this into account.... ie a long cylinder experiences the same force effect as a short cylinder.
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The first part of your quote goes to the "waxed or unwaxed" surface argument that was settled (as far as I'm concerned) some time ago. Yes, to some extent the smoother a surface the less boundary layer interference and in return there will be less surface frictional drag coeffecient. But to every rule there is an exception and the aerodynamics field is no exception. You may be interested in
this book.
Okay. I'll see if I can draw a verbal image. Say you have a series of mountains. As the wind blows over the mountains the wind blows into the valleys. Now suppose you could shape these mountains so the wind would only intersect the peaks of the mountains. What you've basically done is reduce the surface area of the mountain. What my experiment envisions is modifying a surface so the apparent area of surface available to the fluidic forces is minimized. The end goal (I guess) is to find a way to reduce the wake turbulence to as close to zero as possible without using a bunch of fancy wings.
Remember the Reynolds number which is:
RN =rVc / Viscosity
RN = Reynolds Number
r = Air Density
V = Velocity
c = distance over which the air flows
What I'm trying to test is whether it's possible to change 'c' without actually changing the physical length of the vehicle. I know, I know the big cone/small cone theory says bullocks to that. But I challenge that thinking. All those numbers make sense with a
smooth surface. Now, I'm not proposing the old "waxed versus sanded" argument in boating but something that may not have been tried before.
Remember the mountain deal? Well, I look at it this way. If I can break the fluid flow of the air over the vehicle so that it impacts the upper area of the irregular surfaces only in most conditions then the total frictional surface exposed would be less and should require less effort to move through the atmosphere. The question is how to do this. Would we accelerate the air as it intersects the vehicle with a mechanical device or use passive means to proceed over this irregular surface.
Some of them have been solved. I suspect this is an old list.
kitcar 
Hybrid Mode
