Well, I did a search and nothing came up, so i thought that I'd make a new thread.

I think it would be a good idea to incorporate drafting into LFS, I dont know if it already has been, but if it has, well im sorry for wasting a new thread

So do you guys think it would be a good idea?

Just my 2 cents

It is already in.

Oh, ok then, i just wasn't smart enough to notice it :doh:

Yup, already in, and a bit strong, especially in the road cars. REALLY noticable.

Well then ill have to get some moneys so i can get s2 and say goodbye to my social life!

I need a job

Don't you mean, say "hello" to your social life?

Quote from geeman1 :

It is already in.

Only partly.

Drafting in LFS reduces drag for the rear car, but unfortunately the front car doesn't get any reduction. This is a significant limitation in terms of using 'realistic' drafting techniques/tactics (at least with the tin-tops).

As I'm a bit fuzzy with this aero stuff. Is it true that the lead car gets a boost too? This has something to do with the way the air flows between the cars. Less turbulence or was it less vacuumbehind the lead car.

Air drag comes (largely) from two things:
1. Compression of the air as your push it apart to travel though it.
2. Expansion of the air to fill the void you are leaving, creating a suction effect.

As you can imagine, the rear car benefits from reductions to point 1, while the lead car benefits from reductions to point 2.

Hi. I noticed that on LFS manual it says: "By staying behind another car in a draft you increase both speeds of each car allowing for you both to pass faster cars and hold them off. "The bigger the pack the faster you go""
http://en.lfsmanual.net/wiki/B ... Drafting_is_for_straights

The front car really gains speed? I dont remember this being implemented in LFS, but ive been some months away from LFS

No, not as far as I'm aware. TBH that whole paragraph is badly worded and there are other inaccuracies present too.

Quote from Bob Smith :

No, not as far as I'm aware. TBH that whole paragraph is badly worded and there are other inaccuracies present too.

Indeed, the LFS Manual contains many spelling, grammar, sentence structure and clarity issues. It has been my intention for a couple weeks now to start fixing some of them, but regrettably I have not yet gotten around to it.

I'm somewhat confused as to why the air expanding behind a car makes it go more slowly - I thought that seeing as the air is expanding to fill a gap made by the car, it is expanding against the rear of the car, and so an increase in this effect would create a greater push behind the car, and thus greater speed?

I thought the reason the car in front experienced a reduction in drag was something to do with lower turbulence around the rear as the air is cleaved apart by the second car before it has a chance to reform.

Maybe I'm missing something, or maybe my ideas of aero physics are flawed? Maybe both

Sam

Would it have anything to do with negative pressure? I'm completely pulling this out of my @$$ but here's my wild guess:

Normally, as your car cuts through the air, a zone of negative pressure forms behind your car as the air tries to close that space behind you. This causes vortices and stuff, but also the simple fact that there IS a zone of negative pressure tends to hold your car back just a tiny bit. If another car comes in behind you, that negative pressure still exists, but now it is acting on two vehicles, meaning that it doesn't have quite as much of an effect on you alone.

The way I imagine it is if you take a box, with a pointed nose and drag it through the water, the square back end will cause enormous drag. Now if you stretch the box to make it longer (e.g. two cars in this capsule of negative pressure), and pull it twice as hard (two cars in this capsule giving you twice the power) it will still be held back with the same force as the water washes around the back end, but now you can go a decent clip faster.

Does that make any sense?

It's low pressure, not negative pressure.

I don't believe the low pressure behind the second car acts on the first car,
and the second car overcomes it due to the reduced drag.

That's what I meant - low pressure.

I think i depends on the chassis, the amount of downforce and the position and shape of the spoilers. In tin tops for example not only the chassis itself reduces the vacuum area behind it but also the amount of downforce, the shape and position of the rear end spoiler has an huge impact on this "area" due to massively distortion.

Take the GTR cars for example: the spoiler at the rear end is placed not directly on the chassis but like 20 cms away from it.
Now with a decent amount of speed the air can devide into two directions, up or above the wing and down or underneath the wing. The air that is going underneath is basically responsible for the distortion, making it harder for another car to catch the draft. Now the closer this car gets the harder it is to keep control since its front is usually beeing lifted by that air where actually the vacuum area should be and so the push pull effect is almost none existent.

But of course, if the second car is getting close enough and i mean really really close then it should be possible again to drag away together. The only problem would be that the second car had to look out for the engine temperature since there is no fresh air reaching it.

Now take a stockcar like NASCAR for example. There the wing is directly attached to the chassis making it basically impossible for the air to have any influence on the vacuum area behind the car. If then another car is reaching this area the push pull effect due to massive pressure is taking effect making both cars faster as long as they are lined up.

This is just my personal understanding of it and so please correct me if im wrong, thank you

Possibly, but that would be detrimental to the rear downforce to have air travel under the spoiler.

It is the same concept as air traveling under the car itself, i believe, and would create lift under the spoiler.

Quote from EvilVendingMachine :

Possibly, but that would be detrimental to the rear downforce to have air travel under the spoiler.

It is the same concept as air traveling under the car itself, i believe, and would create lift under the spoiler.

Yeah but i think that due to the shape of the spoiler the air that is going upwards is actually repsonsible for the downforce. The air that is going underneath is basically just passing through while nevertheless having a huge impact on the area behind the car. (just guessing here)

Quote from 510N3D :

(just guessing here)

Me too lol. The air that is passing through though would
probably create turbulence though as the pressure lowers to fill the void created by the spoiler and rear of the car.

Quote from 510N3D :

Yeah but i think that due to the shape of the spoiler the air that is going upwards is actually repsonsible for the downforce.

Correct. It's a Newton's Third Law type of setup. Air pushed up by the wing pushes the wing and car into the ground.

Quote from Stang :

Normally, as your car cuts through the air, a zone of negative pressure forms behind your car as the air tries to close that space behind you. This causes vortices and stuff, but also the simple fact that there IS a zone of negative pressure tends to hold your car back just a tiny bit. If another car comes in behind you, that negative pressure still exists, but now it is acting on two vehicles, meaning that it doesn't have quite as much of an effect on you alone.

Ahh.. Of course.. The lack of air in the space the car has just vacated causes a much lower pressure, so everything around it tries to move into the space - including the car, hence the backwards pull on it. Thank you very much for that

As for the wing making the drafting effect harder to exploit, I'm not convinced: my reckoning is that the amount of air the wing displaces more than makes up for the splitting of the air currents, which I suppose is why cars with greater downforce are easier to draft - they're interfering with the airflow more to create higher pressure above them, which pushes them down onto to road, and so the air behind them takes longer to reform / is at a lower pressure.

Air travelling under the spoiler isn't necessarily a bad thing - so long as it is slowed down. Air moving slowly underneath the spoiler surface, I believe, results in a lower pressure, and so the spoiler - and the arse-end of the car attached to it - tries to move down to occupy the lower-pressure air. This effect is increased by the faster-moving air above the wing creating higher pressure, as the wing is now under a double effect - high pressure above pushing it down, and low pressure below encouraging it to move down.

Please do correct me if I'm wrong, I'm using reversed aeronautic teaching here

EDIT - Ignore this if you know what's good for you I managed to reverse the physics rather than the way they're employed!

Sam

Quote from Dark Elite :

Air travelling under the spoiler isn't necessarily a bad thing - so long as it is slowed down. Air moving slowly underneath the spoiler surface, I believe, results in a lower pressure, and so the spoiler - and the arse-end of the car attached to it - tries to move down to occupy the lower-pressure air. This effect is increased by the faster-moving air above the wing creating higher pressure, as the wing is now under a double effect - high pressure above pushing it down, and low pressure below encouraging it to move down.

Well, I don't know much about how wings are set up, but assuming that the air under the wing IS moving faster (either due to the shape of the bottom of the wing, or the shape of the car making that air move faster) it WOULD create low pressure pulling the car towards the ground. But at the same time, that's simply going to pull UP on the car's body under the wing, so unless the air under the car's body is moving even FASTER , it kind of cancels out that effect.

Also, I don't think that the the wing is set up to generate faster-moving air on top compared to that underneath. The wing is tilted forwards, which means the air hits it, and get's shoved UPWARDS, which creates the effect of pushing the wing into the ground. If anything, this effect would create turbulence in the air above the wing, slowing it down, which means the faster, less turbulent air underneath the wing would create en extra bit of downforce as well. In other words, the wing does not function on the principle of the Bernoulli Effect, but is simply based on Newton's Third Law.

...or not. I'm only a Freshman Aerospace Engineer - so I have yet to take all those hydrodynamics courses and stuff...

Quote from Stang70Fastback :

Correct. It's a Newton's Third Law type of setup. Air pushed up by the wing pushes the wing and car into the ground.

Right, are your sure you understood the context in which i made this statement correctly?

Quote from Stang :

I think you got a little mixed up when you started talking about the air over the wing. The faster moving air there would actually pull UP on the wing, not down.

I'm now completely stuck between deciding whether air moving more quickly results in a higher pressure or a lower pressure. Air moving more quickly means that air doesn't need to be in the same place for as long, resulting in a lower atmospheric pressure, but also that more air hits the surfaces of the wing, resulting in a higher pressure on that. Which effect is greater?

Better find out before I go any further on this one

Sam