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Originally Posted by Pooft Lee
Here's where I get a little confused. Does turbulent attached flow produce more drag than laminar or vice versa? I understand the reduced wake is the end game, but is that the only plus to the dimpling?
If so, it makes sense a plane with a no-compromises shape wouldn't have the same separation issues and wouldn't want to run around chopping up air
I'm also curious what you mean by a car is mostly profile drag vs the plane
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*Automotive streamlining is about reducing,or eliminating flow separation,almost exclusively in the afterbody.
*If you have separation,the kinetic energy of the turbulence of the separated flow can never be reclaimed.
*If you don't have separation,the afterbody flow will decelerate,lose it's velocity,gain pressure,and when it leaves the rear of the car,will be at it's highest possible pressure,which reduces pressure drag,the primary component of profile drag.
*A turbulent boundary layer will allow fully attached laminar flow "IF" the body is shaped in the back like the 'template.'
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*Dimpling was a way to increase the Reynolds number of little golf balls to a supercritical value,to force the transition from a high-drag laminar boundary layer,to a low-drag turbulent boundary layer.
*Without the dimpling,even at 110-mph off the club head,the wake would be enormous and they wouldn't make it far down the fairway.
*Vortex generators(real ones !)would improve the range of all golf balls,compared to dimpled balls,but as soon as you struck the ball with the club they'd be destroyed.
*The dimple is a practical compromise,providing artificial roughness to force the LBL-toTBL transition.
*No matter what direction the ball is placed on the tee,the air effectively 'see's' the same 'face' of the ball as it flies toward the green.
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*Aircraft are very long in relation to their width.
*These large fineness ratios make pressure drag virtually impossible.
*Their enormous exposed surface area is responsible for the lion's share of their drag.
*TBL surface friction is higher than LBL surface friction.
*The lowest drag "laminar" aircraft hold the widest portion of their wing and fuselage very far back to postpone the inevitable 1st-minmum-pressure which forces the LBL-to TBL transition.
*"Laminar" aircraft is kind of an oxymoron.All aircraft have turbulent boundary layers.It's just that they're minimized as much as possible.
*Aircraft are also designed for 'flight conditions',at a given altitude and velocity,trimmed for lowest drag,in the thinnest air that they can operate in.
*Aircraft and automobiles serve completely different masters and their design paths diverged a long time ago.