Do you gain draft while close to wall?

[Tank-Ceo]

Or is that just in real life?

 

[mjake56]

I noticed during my Indy 500 endurance that I gained about 10-15mph at end of straight by drafting the wall with the Toy GT-ONE. I had ALOT of time to experiment! GT5 is as REALISTIC as it gets.

 

[Noren]

How do you gain draft from a wall? Doesnt draft come from another car that breaks the wind? Or have i completely misunderstood the concept of draft?

 

[Blitz24]

Or is that just in real life?

The wall does act as a vacuum cleaner in some instances, especially on the ovals where if your car hits it it becomes stuck to the wall. I haven't noticed any significant effect in speed though if one were to run right next to the wall as opposed to near the bottom line on the straights.

 

[nvmy3g]

How do you gain draft from a wall? Doesnt draft come from another car that breaks the wind? Or have i completely misunderstood the concept of draft?

I'm with you on this. ^
In order to gain draft while next to something, that "something" needs to be motion as well so that it reduces the air resistance on your car.

The wall does act as a vacuum cleaner in some instances, especially on the ovals where if your car hits it it becomes stuck to the wall.

The vacuum effect you speak of comes from the air only pushing on one side of the car, therefore keeping you pinned against the wall until your speed reduces enough to get off the wall.

 

[Troux]

The wall does act as a vacuum cleaner in some instances, especially on the ovals where if your car hits it it becomes stuck to the wall.

Ugh...No.

Look up Bernoulli's law for a warm up. It's the same effect as lowering your car, in terms of aerodynamics. The smaller the gap between the car and the wall, the less air there is physically there, the faster that air moves, and the more laminar its path. Now theoretically if you were driving a car that was lowered to .01" off the ground and driving .01" off the wall, you would only have aerodynamic drag on the front, top, and one side of the car.

I've never heard a specific racing term for this, but I don't think it's "drafting a wall," as it's very different from the concept of drafting a car, in which you get caught in an airstream of already accelerated air that's already taking a path around the outside of your car.

 

[Noren]

I must say i had never heard of wall drafting before. And i guess we must say its busted!

 

[alextehkid]

I can't imagine there beeing any truth in gaining speed from a wall. Draft from the side of the car also seems far fetched. Draft should only matter in the direction you're traveling.

If anything, driving next to a wall should slow you down.The air displaced from the front of the car would have to be channeled above or to the opposite side of the front, creating more draft. Also, its not very realistic that drivers would "hug" the wall at speeds above 300 km/h.

 

[Exorcet]

The wall does act as a vacuum cleaner in some instances

Ugh...No.

Look up Bernoulli's law for a warm up.

What he described was Bernoulli in a very rough form.

 

[jmeGT5]

The video before the Nascar challenges says to also draft/stay close the walls iirc. Ideal if your position no1 trying to get some space between you and the cars following

 

[Smelly Llama]

Ugh...No.

Look up Bernoulli's law for a warm up. It's the same effect as lowering your car, in terms of aerodynamics. The smaller the gap between the car and the wall, the less air there is physically there, the faster that air moves, and the more laminar its path. Now theoretically if you were driving a car that was lowered to .01" off the ground and driving .01" off the wall, you would only have aerodynamic drag on the front, top, and one side of the car.

I've never heard a specific racing term for this, but I don't think it's "drafting a wall," as it's very different from the concept of drafting a car, in which you get caught in an airstream of already accelerated air that's already taking a path around the outside of your car.

This makes logical sense.

 

[MidianGTX]

If you think air behaves exactly the same beside a wall as it does out in the open... you must be unaware that air actually moves. Whether or not it acts in a positive or negative way I'm not sure, and if it does I kinda doubt it's been implemented into GT5, but there's definitely a difference in real life. I'm sure some Nascar pros would be able to say something on the subject.

 

[TenEightyOne]

If you think air behaves exactly the same beside a wall as it does out in the open... you must be unaware that air actually moves. Whether or not it acts in a positive or negative way I'm not sure, and if it does I kinda doubt it's been implemented into GT5, but there's definitely a difference in real life. I'm sure some Nascar pros would be able to say something on the subject.

From the hundreds of laps I've done whilst tuning my Nascar I can assure you that there is definitely speed to be had by riding the wall in GT5.

In real life (I'm avoiding IRL due to the potentially confusing oval-racing connotation ) cars gain an advantage by running close to the wall because they lose 50% of the drag at the sides of the car. Frontal/rear resistance and drag remain (mostly) unchanged of course.

Bernoulli's law is quite complex but will, with study, yield highly detailed answers as to why this is the case... I've merely tried to give the simplest explanation I can.

 

[1Fast335i]

Ugh...No.

Look up Bernoulli's law for a warm up. It's the same effect as lowering your car, in terms of aerodynamics. The smaller the gap between the car and the wall, the less air there is physically there, the faster that air moves, and the more laminar its path. Now theoretically if you were driving a car that was lowered to .01" off the ground and driving .01" off the wall, you would only have aerodynamic drag on the front, top, and one side of the car.

I've never heard a specific racing term for this, but I don't think it's "drafting a wall," as it's very different from the concept of drafting a car, in which you get caught in an airstream of already accelerated air that's already taking a path around the outside of your car.

My expertise is Electrical Engineering but I remember some of my fluid dynamics and this is correct.

 

[Duo64]

On a somewhat related note about drafting, I have noticed that when I am drafting someone and have to brake into a corner, it seems that the brakes do not work as well. I then thought about it and assumed that because there is less air resistance during a draft, brakes wouldn't work as well. Is this actually happening or am I just imagining things? Or is my physics just completely wrong?

 

[dylansan]

Air resistance helps slow the car a lot on its own, but in real life drafting can also cause the brakes to overheat as no air is flowing over them to cool them.

 

[Duo64]

Really interesting fact, never thought about that actually. I wonder if GT5 with its obvious lack of thought put into brakes (no brake upgrades, etc) actually put that into consideration as well?

Air resistance helps slow the car a lot on its own, but in real life drafting can also cause the brakes to overheat as no air is flowing over them to cool them.

 

[Novice]

I must say i had never heard of wall drafting before. And i guess we must say its busted!

unlike you adam, i think the propositions show something.. and i say it's plausible! 💡


@Topic

staying close to the walls reduces air resitance irl. it's not called drafting tho, but i get what you mean.

 

[Exorcet]

The CFD I just ran said there is a drag increase with wall, but I only did a very basic run (and I made the model asymettric without realizing, which throws off the results. I might do a better one later).

200 mph car near wall
Drag: 564 lb
Lift: 1285 lb
Lat: 241 lb (into wall)

200 mph car no wall
Drag: 544 lb
Lift: 1381 lb
Lat: 55 lb

 

[Novice]

The CFD I just ran said there is a drag increase with wall, but I only did a very basic run (and I made the model asymettric without realizing, which throws off the results. I might do a better one later).

[..pics snipped..]

dang..that's incredible. can you teach me CFD? i'll use it for my r/c touring cars..

 

[Tank-Ceo]

Air resistance helps slow the car a lot on its own, but in real life drafting can also cause the brakes to overheat as no air is flowing over them to cool them.

Wheels, especially stock wheels for example of a 300zx are designed to funnel air flow into the brakes to cool them.

 

[Troux]

My expertise is Electrical Engineering but I remember some of my fluid dynamics and this is correct.

ME here, but I'm fascinated with fluid dynamics, specifically automotive-related.

Anyone remember the Top Gear last season (I think it was...) where they had to build the perfect camper? May had a piggyback station wagon basically, Hammond had the panels to build a fort stored in his car, and Clarkson had a ~25 foot tall stacked mobile home. When they were driving down the road, he would get TERRIFIED when a large truck passed him, as the car would sway uncontrollably (I've done this to a lesser degree too often). The same principle is being applied; as the large vehicle passes the other large vehicle, it creates a narrow channel between the two vehicles (smaller vehicles would let the air disperse over them). The air, "squished" between the vehicles, is forced to move faster, which creates a low pressure area, pulling the vehicle to one side, while creating less drag.

 

[Exorcet]

Update, slightly better model

200 mph car near wall
Drag: 614 lb
Lift: 1148 lb
Lat: 261 lb (into wall)

200 mph car no wall
Drag: 533 lb
Lift: 1286 lb
Lat: 23 lb

The air, "squished" between the vehicles, is forced to move faster, which creates a low pressure area, pulling the vehicle to one side, while creating less drag.

The thing to remember is that pressure is a normal force. Low pressure on the side will not reduce drag. What might be happening is that there is a small drop in pressure ahead of the vehicle, but the pressure drop on the side has no effect on drag because drag will change with Reynold's number, not pressure. Drag changes with density, but at the speeds car travel at, air is not compressible.

 

[Lynyrd_Skynyrd]

GT5 is as REALISTIC as it gets.

Sarcasm?

 

[vett'e]

Its called the Venturi effect, basically the air has to travel faster when the volume decreases. So the closer you drive to the wall, the faster the air has to flow between your car and the wall. This creates differential pressure thus forcing the car to 'stick' against the wall.

Its a lot like how a diffuser works, except much more fundamental.

 

[Egghead43]

Well, this is one of the more interesting threads I've read lately. It sure beats all the whining about grinding to get credits, and how the shadow aren't perfect...

It seems that this topic is a bit inconclusive in the real world; what's most relevant here though is how the game was programmed.

After a bit of Googling, I came across this paper: http://www.cfd4aircraft.com/int_conf/IC2/proceedings/papers/r_strachan.pdf

I haven't bothered to read through it all yet, but it didn't seem very conclusive.

 

[PS3LUV3R]

Call Mythbusters.

 

[mjake56]

O.K., I'll own it, I have not been able to recreate my posted results after trying again. Same car, same race, same speed against the wall vs middle of track. Not sure what I was zoning on? Seems the rpm's pick up quicker, but as for top speed, the same. My bad.

 

[Sndr]

Very interesting topic.

Dont know enough abouth aerodynamics or physics in that matter. But i noticed my lap time dropped a lot when i stayed as close as possible against the walls on the long straights in daytona.

This counts for the FGT, Toyota GT-One and for the ZR1, that i know for sure.

 

[Troux]

Update, slightly better model

200 mph car near wall
Drag: 614 lb
Lift: 1148 lb
Lat: 261 lb (into wall)

200 mph car no wall
Drag: 533 lb
Lift: 1286 lb
Lat: 23 lb





The thing to remember is that pressure is a normal force. Low pressure on the side will not reduce drag. What might be happening is that there is a small drop in pressure ahead of the vehicle, but the pressure drop on the side has no effect on drag because drag will change with Reynold's number, not pressure. Drag changes with density, but at the speeds car travel at, air is not compressible.

Sorry, I knew that, but I meant to differentiate the two. The low pressure pulls you to one side, while the less air and less turbulent air are what create less drag.

I did notice this in the game (Did the Indy 500 last night, nothing better to occupy my mind with...), but you have to be REALLY close to the wall. Strange your CFD is saying otherwise...