Ground roll and take off dynamics

[maxkang]

What type of drag(among form,skin friction, and induced drag) contributes the most towards the total drag on ground roll before takeoff and after takeoff? My initial guess was that induced drag would be quite small for ground roll due to the ground effect(in absolute terms) but after doing simple math to find the induced drag coefficient, it seems that there will relatively be a lot more induced drag than other types of drag. What I am not sure about is the relative amounts of each at zero AOA. If the percentage of each can be also given, that would be really awesome!

Thank you,

[redneck]

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Curious...

Why all the airplane talk on a automotive forum ?

Are you planning on building a sky car ?




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[maxkang]

oops sorry.. I just saw "aerodynamics" section and thought it was for any kind of field that involves aerodynamics

[skyking]

Here is the short answer.
During the ground roll, Tire friction is a significant portion of the total force to overcome in the first portion. Then as speed increases parasite drag, and parasite drag only that is added.
There is no induced drag until the aircraft has an angle of attack. It all comes back to that.
On the ground most planes have a negative angle of attack until it is pitched up and nosewheel lifted. This is called rotation.
At that moment you start to generate lift. The wings bend as they are loaded.

[ChazInMT]

Hey Max, the more we look into automotive aerodynamics, the more we learn we have a lot to learn.

While I appreciate the vote of confidence you have given this humble forum to pose such a question thus expecting one of our learned followers to give you a good answer, sad truth is, no body here probably knows the answer you seek for certain.

You may also want to know that some members here feel that while cars and airplanes do indeed each move through the air, each operates under such different circumstances that they are seen as 2 differing worlds.

I hope this helps you understand why some here may not give you a proper response.

(except SkyKing....he might know)

[skyking]

It's no problem Chas, I think that in terms of how lift or downforce adds to drag on our cars, it all adds to the discussion.

[jcp123]

Some of the best innovations have probably come from discussions or overhearing discussions at the water cooler or Xerox machine, where people of different disciplines come together.

I really wish I remembered the title of the book, there was one whose subject was where creativity came from. The interview was fascinating and the author pointed to a lot of chance meetings between various people and having an AHA! moment which moved something forward.

So I'm actually fascinated to see these aero discussions, even if it's a little over my head and I myself can't quite grasp a connection to the subject.

[ChazInMT]

It's funny I was writing my response based on the #2 answer here and wanted the OP to brace themselves, and maybe start gain insight that planes and cars have less in common than one might think. The I hit enter and it's like....OH. Ha ha ha. All good fun.

[gone-ot]

CARS = aero devices NOT designed to FLY.

[skyking]

To take that a step further tele man, to not generate lift in ANY direction...
at least at speeds that are conducive to economy and not racing.