I tried to figure out how to make a real small drag into a 4 seater car, thus going 55 mph at 0,5 gallons / 100 km ( MPH 124 ).

I had roughly drag coefficient 0.17 here. This mean very low and clean body...not very practical for inner city driving.

Dimples would certainly lower the drag.

topspeed,

It's possible that dimples would help reduce drag for that shape, but it depends on several things. If the flow tends to separate early, say around the top edge of the backlight, then forcing the flow to transition to turbulence before that point could delay the separation, thus reducing drag. However, if the flow is already turbulent by that point, then adding dimples probably wouldn't have any effect. It's also worth noting that there's nothing special about dimples; other kinds of surface features can be used to generate turbulence. For example, a fairly small ridge at the top of the windshield, which might exist anyway, could be an effective turbulator.

If the boundary layer naturally stays laminar and attached all the way back to the sharp rear edge (unlikely, I would guess), then no kind of turbulator would help. There's no way that the boundary layer would stay attached past that point, turbulent or not, so inducing turbulence in that case wouldn't reduce drag at all.

banktoturn

Exactly as banktoturn says. There's nothing at all magical about dimples. They are just ONE form of turbulator that happesn to work on golf balls. Raised pimples would work just as well but the clubs would beat them inward so dimples are used to avoid being damaged by the impact with the clubs.

In airplanes a wide number of variations on turbulators or invigorators are used. They all work just fine.

Topspeed, instead of the shape you show what you should be doing is running the upper surface shape through something like Xfoil and design it to avoid any sudden pressure transitions that would lead to the need for turbulators. Some fudging on the car would be needed due to the extremely small aspect ratio. Also it's been shown in a number of other efficiency cars that cowling in the wheel wells is highly benificial to better mileage. Or if that isn't practical as on the front then smooth wheel hubs and a curled in rear edge to the wheel well to aid the trapped air to get back out onto the outer side skin could be benificial. Also by far the more aerodynamic design is the long tail that extends well back and tapers off to nothing. This was proven very ably by the old Porsche long tail LeMans racers. They swept the field and within a year or two an overall length or maximum overhang length rule was introduced. But since those sort of tails are not practical the Kamm cut off tail is the best compromise. And best of all it helps pull up air from below the car and thus aids traction at higher speeds.

Your wheel wells will also need blisters above them. As shown you do not have a realistic clearance for suspension travel.

Otherwise it's a highly interesting doodle though. Nicely done.

Right I was able to reduce the drad further when I tried to see how a flying car version of that low D car could look like.

The suspension could be like in Gumpert Apollo. It also seems to have almost no room to work for the suspension albeit it has 700 hp engine on it.

dimples break up laminar flow. without laminar flow planes wont fly. No thats not right. Da^%it now I gotta get a text book out.

I am afraid that this car would produce a significant amount of lift. Lift equals drag and worse, it make it very unsafe at speed.
To design a car, you need to look at as a three dimensional object. Also, I don't know where you are getting your drag "number" but I don't believe it.

In an ideal world the laminar flow offers the least drag. But laminar flow is not a requirement for producing lift at all. The wings can do just fine with tubulent flow over them. And remember that the goal of using dimples, trip strips, sawtooth strips, raised tabs or any other form of turbulation is to generate a very thin layer of tubulent flow next to the airfoil's skin. It's not like we're talking about forcing the airflow away from the wing.


Why we resort to generating this turbulence on purpose is because due to other choices or factors our wing may not be able to support a good laminar flow over the entire chord over the whole range of lift coefficients we want to achieve. Especially at the higher angles the laminar flow can separate. When it does this from a laminar state it forms much bigger, and therefore more draggy, bubbles or an earlier stall than the same airfoil would if it had some way of inducing a thin turbulent flow. A thin layer of turbulences acts like a stickly layer to hold the laminar flow close to the airfoil's skin under harsher conditions.

And conditions do not get any more harsh than with a sphere. Whether lesser drag due to a smaller wake or to enhance the Magnus effect to generate lift to fly further is a moot point. Regardless of which reason was primary the dimples do act to reduce the size of the wake. And a smaller wake means less drag. And while it's sort of a happy "Two For One" solution the primary point for this discussion on aerodynamics is the drag issue..

A drag race does not necessarily have a drag queen at the event. Also the sticklers for "kerect" aerodynamic terninology don't all agree on what is parasitic or induced or transitory.
I remain steadfastly attached, thu a semantic layer, to the belief that drag n lift are the same thing - If it helps do a job that needs to be done - I christen it lift -If it gets in the way - it becomes drag.
Keeps life simple and easy to negotiate.

If that makes it easier for you, stick with it. I do the same with batteries, Nicad and Nimh, are all "Nicads" to me when I am including Lipo's in the discussion. But I wouldn't argue with someone who is a stickler for the correct terms because they may have their reasons. Same with the Lift/Drag issue. To me they are not the same and do not act in the same direction on an object. As far as wings are concerned lift and drag occur at the same time in directions perpendicular to each other. But if you can keep that straight in your head while interchanging the terms then its fine with me as long as your're not trying to argue your point against mine!

You may have a group of sticklers in mind who don't agree on the definitions of different components of drag, but they are unambiguously defined. That some people get it wrong doesn't change that.

I seem to recall that you have, in the past, cited some useful functions of drag. This would seem to be inconsistent with your statement here. How about this: you need your plane to either slow down or lose altitude without speeding up excessively, in order to land. Do you now claim that the force that I would call "drag" has just become "lift", simply because it is doing something that you want?

Drag and lift are unambiguously defined, and they are not the same. You can remain steadfastly attached to a different view, and you will simply be contrarian and incorrect. This is fine until someone earnestly asks a question about aerodynamics and you give them a faulty answer. I find that to be unhelpful at best, and just plain silly.

banktoturn

Exactly what I meant but worded much better than I did.

Well- consider the "WALL" We fly along at a good clip then -chopping power and at the same time -we pitch the model and return power as needed to make a transition from say 40mph to a 25 mph forward speed recovery -OR simply balance power (vecotored flight)and AOA till the model is stationary in a vertical hover . altidude remains constant
How would you describe the event?

Not realistic?
How about the notorious OSPREY?

In that case you have changed the pattern of air flow over the wing. As this happens lift is lost and the underside of the wing is actually now a very large leading edge, and yes, drag may be created behind it, but is still oposing the direction of the plane's travel until the point foward travel stops and the "hover" beggins.

Since we're in the mood to haggle, let me try another explaination. If you could magically remove drag and gravity from a plane in motion, lift would constantly pull the plane in a loop, but would do little or nothing to slow it down. However, if you could remove lift and gravity, drag would still slow the plane down by directly opposing its foward motion.

So the lifting surface becomes a drag surface -
OK
Ot lets say the low pressure which was on th top surface simlply becomes VERY low pressure as the wing rotates.
T/F?
The lift is then drag.
It's all the same thing - just depends on what you want to call it

Is there a question in there somewhere? Perhaps you could find some subjects and predicates, and arrange them into some coherent sentences. For goodness sake, if you're here to communicate with people, take it seriously enough to be understandable.

Then why is it that I can understand him ????

Concerning the "low pressure" or "wake" area, you are partially correct. When the wing is at low AOA and in forward motion, lift is created along the top surface due to "Bernoulli's" law, but this is not the same as what is happening at the back edge of the wing or "wake". When the wing is rotated in your scenario, the low pressure area behind the wing does become "very low" pressure, which is "drag". Even if you take this away, you still have another type of drag along all surfaces of the wing in which air is moving past due to "friction".

Yup - all kinds of drag- depending on what the source or what the result etc., we give it a "speshial" name -but still - we are simply working with low pressure.
good low pressure n bad low pressure -
if you attach a large plate to strings and then attach that plate to a harness and then stuff a parachutist into the harness - he may "fly" that plate sideways or even do a loop d loop.
sometimes th plate is actually lifting -sometimes just retarding the journey to earth
so is the air above the plate shifting from lift to drag?
Or is the pressure distribution above and below simply changing .
For years Iwas told "you need a proper airfoil to create lift
Never could figure THAT one out - turns out the fact was simply horse pucky.

<div style="margin: 0in 0in 0pt"><span style="font-size: 9pt">This reminds me of an aircraft that has circumnavigated the earth using drag exclusively as a means of horizontal acceleration. The faster it goes the less drag it generates until it reaches top speed, which can be as much as 250mph where drag is zero. This aircraft generates no aerodynamic lift and its weight is opposed by aerostatic lift.One of the last great accomplishments it aviation was the round the world flight of a balloon, the first aircraft to fly. </span></div><div style="margin: 0in 0in 0pt"></div><div style="margin: 0in 0in 0pt"><span style="font-size: 9pt">Propeller driven airplane use propeller lift as a means of thrust so if you remove lift you will remove thrust so it will pretty much have the same flight dynamic as a balloon. </span></div>

Good example, but again I must point out that this "drag" that propels the balloon is caused by wind moving past the balloon at a speed faster than the balloon itself is moving. Thus the relationship is still the same, the "drag" on the balloon is still oposing the "relative" direction of the balloon and the air.

Who ever told you that didn't complete the sentence. You can create lift with almost any object if you have enough velocity of air moving over it. However, you must have "THE PROPER AIR FOIL" to create "ENOUGH LIFT" to overcome the effects of gravity on any given object at a given velocity!

Hypothethical case in point, try to put the wing from an F-14 on a Cessna Citation and see if generates enough lift to fly.

I just fly 'em, I don't know how they work! Not being a very tech-no kind of guy, it is interesting to see the level of knowledge that a lot of the people in this hobby have. Keep going, I am learning.

Its possible that its mostly oh what was the vernacular? horse pucky