Aerodynamics on racecars
12-01-2013, 10:56 PM
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Aerodynamics on racecars any good books on the subject? the stickies are focused on engines.
ETA for discussion purposes:
Essentially, we can look at airflow around, over, and under the car like we do in an engine. It wants to act the same ways and almost all aspects apply.
Under the car:
Here is basically the biggest problem are for every lower tier car. Its muddied up with suspension pieces, exhaust, differentials, etc. This creates turbulence, traps air, and in some cases.. causes lift. On the 4th generation FBody, the car is designed to have air come up through the a/c and radiator then down through the underside of the car. Odd, but it works. Thing is.. thats about the extent of the good.
If one had double diamond type sfc's, one could clean up (flatten) a large part of the underside of the car. The D/S tunnel and rear section would still be an issue. Getting air around the axle and to a diffuser..that worked.. is a major sticking point with how everything is arranged.
A major part of the downforce available to the 6th generation Sprint Cup car is the fact that the underside is sealed to the race track. The front splitter is on the ground in the turns and for good reason. It keeps air from getting underneath. On the FBodies, one would have to lower the car and come up with a splitter that, while not as extreme a the NASCAR version, would still have to help keep air from getting under the car. 6lietereaters splitter could work but, it needs to be extremely stiff and unable to deform. Sideskirts(ground effects.. banned in F1 btw) seal the sides to keep the air from spilling out the sides or working its way underneath as it goes down the doors.
From here, you treat the underside like the intake runner in an internal combustion engine. You want the highest velocity and highest flow possible under there until it rejoins after the rear bumper (hence.. diffuser). Familiar eh? Air doesnt like turning. The radius of the turn at the exit has to be a such that air doesnt detach until when we need it to. Strange, thats a lot like the short side radius in a cylinder head..>.>.
Done right, spoilers and wings can add downforce with minimal or no drag penalties. Its all about working with teh airflow and gently getting it to where one wants it to go.
Mind you, this is a basic understanding and isnt anything close to a 'hey, I know how to shape an F1 car'. And.. GO!
ETA for discussion purposes:
Essentially, we can look at airflow around, over, and under the car like we do in an engine. It wants to act the same ways and almost all aspects apply.
Under the car:
Here is basically the biggest problem are for every lower tier car. Its muddied up with suspension pieces, exhaust, differentials, etc. This creates turbulence, traps air, and in some cases.. causes lift. On the 4th generation FBody, the car is designed to have air come up through the a/c and radiator then down through the underside of the car. Odd, but it works. Thing is.. thats about the extent of the good.
If one had double diamond type sfc's, one could clean up (flatten) a large part of the underside of the car. The D/S tunnel and rear section would still be an issue. Getting air around the axle and to a diffuser..that worked.. is a major sticking point with how everything is arranged.
A major part of the downforce available to the 6th generation Sprint Cup car is the fact that the underside is sealed to the race track. The front splitter is on the ground in the turns and for good reason. It keeps air from getting underneath. On the FBodies, one would have to lower the car and come up with a splitter that, while not as extreme a the NASCAR version, would still have to help keep air from getting under the car. 6lietereaters splitter could work but, it needs to be extremely stiff and unable to deform. Sideskirts(ground effects.. banned in F1 btw) seal the sides to keep the air from spilling out the sides or working its way underneath as it goes down the doors.
From here, you treat the underside like the intake runner in an internal combustion engine. You want the highest velocity and highest flow possible under there until it rejoins after the rear bumper (hence.. diffuser). Familiar eh? Air doesnt like turning. The radius of the turn at the exit has to be a such that air doesnt detach until when we need it to. Strange, thats a lot like the short side radius in a cylinder head..>.>.
Done right, spoilers and wings can add downforce with minimal or no drag penalties. Its all about working with teh airflow and gently getting it to where one wants it to go.
Mind you, this is a basic understanding and isnt anything close to a 'hey, I know how to shape an F1 car'. And.. GO!
Last edited by Wnts2Go10O; 12-13-2013 at 06:22 PM.
12-02-2013, 11:22 PM
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Check out Carroll Smith's book: Tune to Win.
There is a decent amount of information in there about aero. It is pretty well laid out with some practical applications.
Plus the rest of the info in the book is good.
There is a decent amount of information in there about aero. It is pretty well laid out with some practical applications.
Plus the rest of the info in the book is good.
01-01-2014, 07:34 PM
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F1 is the most advanced but also the most restricted I guess due to other limitations however, with so much aero the cars would be travelling at very high speeds through the turns, which increases risks for the drivers and puts a lot of pressure on tire manufacturing which still cannot make tires live at such high G's. Sideskirts and a tunnel connected to the rear diffuser is designed to increase air velocity under the car which then creates a low pressure zone sucking the vehicle to the ground. Its downforce without the compromise of added drag which does nothing but slows you down.
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01-02-2014, 12:25 AM
#8
F1 is the most advanced but also the most restricted I guess due to other limitations however, with so much aero the cars would be travelling at very high speeds through the turns, which increases risks for the drivers and puts a lot of pressure on tire manufacturing which still cannot make tires live at such high G's. Sideskirts and a tunnel connected to the rear diffuser is designed to increase air velocity under the car which then creates a low pressure zone sucking the vehicle to the ground. Its downforce without the compromise of added drag which does nothing but slows you down.
Chris
01-03-2014, 06:41 PM
#10
Chris
01-05-2014, 01:26 AM
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Aerodynamics modeling typically doesn't transfer all that well, but there are some things that can matriculate. Front wing profile studies are something that can be helpful. Rear wings are far too dependent on what's ahead of them and the diffuser below, as they help evacuate the exits. The underwing is usually specific to each type of car due to its complexity in the way of various geometric and rules constraints. All the add-ons (barge boards, vortex generators, turning vanes, strakes, etc.) are highly specific. I've seen ideas work beautifully on one car and ruin another.
Chris
Chris
i understand that every car is different. some parts and pieces may not need to or could be used. however, im trying to 'think like air.' im not speaking of just throwing things at it. i wouldnt use the same profile or style of wing on an F1 car on a Camaro
. i also wouldnt use their DDD/bottom rear wing element setup. on the other hand, i could see someone crazy enough making use of the double deck diffuser in some way without the wing.lets use just a 4th generation FBody as the example. we wouldnt get it perfect but, what do you see that you could do? how do you see air flowing around the car and what points do you see that need help?
01-05-2014, 11:47 PM
#12
i understand that every car is different. some parts and pieces may not need to or could be used. however, im trying to 'think like air.' im not speaking of just throwing things at it. i wouldnt use the same profile or style of wing on an F1 car on a Camaro . i also wouldnt use their DDD/bottom rear wing element setup. on the other hand, i could see someone crazy enough making use of the double deck diffuser in some way without the wing.
lets use just a 4th generation FBody as the example. we wouldnt get it perfect but, what do you see that you could do? how do you see air flowing around the car and what points do you see that need help?
. i also wouldnt use their DDD/bottom rear wing element setup. on the other hand, i could see someone crazy enough making use of the double deck diffuser in some way without the wing.lets use just a 4th generation FBody as the example. we wouldnt get it perfect but, what do you see that you could do? how do you see air flowing around the car and what points do you see that need help?
With what I've seen for most road vehicles, the biggest drag reductions will be underneath the car. Done effectively, downforce (or, actually, lift reduction) can be improved there as well. The rear wing question only comes up if there is not enough load on the rear axle. Cars I've played with lose too much front grip when a wing is added. Typically, a lot of work needs to be done up front before a rear wing starts to look attractive. Road cars are generally set up for understeer, both mechanically and aerodynamically as dead customers don't buy more cars.
Chris
01-10-2014, 11:58 PM
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First step would be to look at on-body flow, using yarn tufts or oil drops to see exactly what the air is doing on the surface. Once that is at least somewhat understood, then work on the off-body flow 6-12 inches off the surface. This will tell you about where to start looking for gains.
With what I've seen for most road vehicles, the biggest drag reductions will be underneath the car. Done effectively, downforce (or, actually, lift reduction) can be improved there as well. The rear wing question only comes up if there is not enough load on the rear axle. Cars I've played with lose too much front grip when a wing is added. Typically, a lot of work needs to be done up front before a rear wing starts to look attractive. Road cars are generally set up for understeer, both mechanically and aerodynamically as dead customers don't buy more cars.
Chris
With what I've seen for most road vehicles, the biggest drag reductions will be underneath the car. Done effectively, downforce (or, actually, lift reduction) can be improved there as well. The rear wing question only comes up if there is not enough load on the rear axle. Cars I've played with lose too much front grip when a wing is added. Typically, a lot of work needs to be done up front before a rear wing starts to look attractive. Road cars are generally set up for understeer, both mechanically and aerodynamically as dead customers don't buy more cars.
Chris
have you seen any numbers on how much lift the front end of the 4th gen fbody produces? the 1st gen, i think, can top 200lbs.
seems like the 4th gen would benefit with simple things like an engine bay belly pan of sorts, of vents up near the front of the hood, and some sort of air dam/splitter combo.
i may actually have a use for the manometer i have: measure air pressure at similar points above the hood and below,
03-26-2014, 11:54 PM
#15
"Aerodynamics is for people who don't know how to build engines."
- Enzo Ferrari
Sorry, this was just the first quote that came to mind, lol. But in all seriousness, I'd have to agree with what was stated above, the belly pan / under car close-out panels I believe would be the biggest gains in making a 4th gen a little more slippery. Also, extractors in the hood would aid in preventing lift by evacuating any high pressure air building underneath it (and help cool the car by increasing flow through the radiator). But I believe to have the extractors be effective, you'd have to have a vent in the hood match up to the radiator completely (kind of like the C7 hood), or put the vents high up on the hood, almost at the base of the windshield, too have complete evacuation.
- Enzo Ferrari
Sorry, this was just the first quote that came to mind, lol. But in all seriousness, I'd have to agree with what was stated above, the belly pan / under car close-out panels I believe would be the biggest gains in making a 4th gen a little more slippery. Also, extractors in the hood would aid in preventing lift by evacuating any high pressure air building underneath it (and help cool the car by increasing flow through the radiator). But I believe to have the extractors be effective, you'd have to have a vent in the hood match up to the radiator completely (kind of like the C7 hood), or put the vents high up on the hood, almost at the base of the windshield, too have complete evacuation.
Last edited by 93Z2871805; 03-27-2014 at 12:02 AM.
04-02-2014, 09:52 PM
#16
On The Tree
Cool book, teaches the fundamentals. You can also look at Race Car Engineering, it's a magazine that covers serious tech sometimes.
A flat bottom, like the many of the exotics use, will cut drag. You need to vent the radiator and use ducting to get air to the differential or diff cooler. To extract air from at hood(assuming you have relatively smooth air over the hood), you could either use the cowl or vents after the rad. A small lip in front of the vent will create a low pressure area.
To get downforce underneath you need channels that either get taller at the rear or get wider at the rear, this will give you the low pressure needed to generate downforce. A properly designed diffuser maximizes the underside aero.
One place on a full bodied car that is usually overlooked is the wheelhouses. There are good gains to be made by venting pressure and controlling the airflow.
One of the biggest hurdles to getting meaningful underbody downforce would be getting the car low enough to make the tunnels work and keeping the car flat in the turns while still generating mechanical grip. Big underbody downforce would be really tough on public roads with a street driven car. The crown on most roads would screw things up along with how bumpy most roads are.
I would really like to figure out how to stall a splitter and a rear wing. You could get decent downforce and very little drag when you want it.
A flat bottom, like the many of the exotics use, will cut drag. You need to vent the radiator and use ducting to get air to the differential or diff cooler. To extract air from at hood(assuming you have relatively smooth air over the hood), you could either use the cowl or vents after the rad. A small lip in front of the vent will create a low pressure area.
To get downforce underneath you need channels that either get taller at the rear or get wider at the rear, this will give you the low pressure needed to generate downforce. A properly designed diffuser maximizes the underside aero.
One place on a full bodied car that is usually overlooked is the wheelhouses. There are good gains to be made by venting pressure and controlling the airflow.
One of the biggest hurdles to getting meaningful underbody downforce would be getting the car low enough to make the tunnels work and keeping the car flat in the turns while still generating mechanical grip. Big underbody downforce would be really tough on public roads with a street driven car. The crown on most roads would screw things up along with how bumpy most roads are.
I would really like to figure out how to stall a splitter and a rear wing. You could get decent downforce and very little drag when you want it.
04-02-2014, 10:09 PM
#18
On The Tree
I worked on formula(not F1) cars for a while. You get some pretty good ideas on how to "cheat" playing with spec class cars. Usually, my good ideas were deemed too expensive or got flagged for being outside the rules. I always looked at it from the "if the rulebook doesn't say its illegal it's legal" and my motto: there are 2 kinds of racers, cheaters and losers.
