I remember reading a while ago that warplane designers were doing tests with different "textures" in the skins of the planes to reduce aerodynamic drag, and that they were inspired by the skin of sharks, which apparently has ridges and patterns to help it swim with less resistance.
Has anything like that been tried in an F1 car? I know that the focus in aerodynamics for an F1 car is on generating downforce and that the cars have really high coefficients of drag, but surely, if you could improve the drag coefficient by making air "slip" or flow better past the bodywork while still generating downforce at the wings, it would maybe help fuel consumption figures and top speeds. Or is it simply not worthwhile or wouldn´t make a difference at all?
Aerodynamic improvements in the "skin" of the car?
Started by
TazioN
, Dec 09 2001 07:06
11 replies to this topic
#3
TazioN
-
- 312 posts
- Joined: August 01
Member
Posted 09 December 2001 - 17:21
Lots of info there! Thanks.
#4
Keith Young
-
- 267 posts
- Joined: May 01
Member
Posted 09 December 2001 - 22:06
I work at an airport, and all the planes are smooth except for the rivets. The only other rough surface is by the emergency exits, so i dont see the benefit.
#5
TazioN
-
- 312 posts
- Joined: August 01
Member
Posted 10 December 2001 - 02:01
Originally posted by rough_wood
I work at an airport, and all the planes are smooth except for the rivets. The only other rough surface is by the emergency exits, so i dont see the benefit.
Yeah, but the vast majority of commercial airliners were designed and built years ago. Even newer planes are built in a way that minimizes costs and simplifies manteinance, and arguably, smooth metal body panels help achieve that. If that was not the case, they would be using a lot more carbon fiber and composites in commercial planes. I was talking about fighter jets and other applications where cost is not as important as performance gains.
The article I read was about fighter jets being designed now to enter service in a few years (one of the planes mentioned was the Joint Strike Fighter). If those guys say there's an aerodynamic advantage in texturing the skin of the plane in some way , I believe it.
#6
BRIAN GLOVER
-
- 465 posts
- Joined: November 01
Member
Posted 11 December 2001 - 06:01
Tazio, The golf ball question.
The critical areas or leading surfaces of commercial airliners are very smooth. They are subsonic planes that opporate at no more than .9 MACH. There are compessibility factors but no compression gain at those speeds. The new Locheed-Martin F35, which will replace 8 aircraft, is a MACH 2 airplane with composite construction. It also has stealth properties and therefore first srtike capabilities at sub compression gain. Compessibility is only considered into design approaching 400MPH. There is no such thing as ram air until that velocity. The aerodynamic considerations for a F1 car and its surface texture is vastly different from jet aircraft where temperature is not a factor. Also, If it works on a golf ball at speeds below 150 mph, does not mean it will work on F1 or race cars that spend most of their time at that speed. NASCAR has experimented with paint texture and find smooth is better. Even the thickness of a decal will cause separation.
The drag on F1 cars is awfull and downforce requirements only adds to this problem. To get more lift with less drag is to minimise B/L separation. Various methods of energising boundry are employed. Once again different methods are used on race cars compared to airplanes.The votex generators on upper surfaces of aircraft wings are for sub sonic airfoils at high angle of attacks. IE, early Lears(25 and 35) had so little thrust that it was impossible to hand fly the airplane at its service ceiling. The A of A indicator showed the wing almost critical and with 10% of its generators missing, the wing would stall. Little holes in surfaces subject to separation on some military aircraft at slow speeds, created low pressure from turbine bleed off. Holes on leading edges were high pressure bleeds for deicing. The generators found on Lears are not effective at F1 speeds in such dense air.
The splitters on F1 cars are for very different reasons than splitters on supersonic aircraft. Because of so many unaerodynamic things sticking into the wind causing much turbulence on surrounding surfaces, their use is for simply sparating turbulent air far from the boundery layer and tidying up vortices before entering other important areas. (Sidepods etc.)
Some discoveries with smart paint ( changes color with pressure) in wind tunnel analysis, showed that in some areas aft of leading edges, orange peel paint surfaces reduced temperatures and extended the boundery layer. This was not the intended use of the paint as it was meant to analyse shapes. It seems air shearing in pockets narrowed the B/Layer. Sorry about the length.
The critical areas or leading surfaces of commercial airliners are very smooth. They are subsonic planes that opporate at no more than .9 MACH. There are compessibility factors but no compression gain at those speeds. The new Locheed-Martin F35, which will replace 8 aircraft, is a MACH 2 airplane with composite construction. It also has stealth properties and therefore first srtike capabilities at sub compression gain. Compessibility is only considered into design approaching 400MPH. There is no such thing as ram air until that velocity. The aerodynamic considerations for a F1 car and its surface texture is vastly different from jet aircraft where temperature is not a factor. Also, If it works on a golf ball at speeds below 150 mph, does not mean it will work on F1 or race cars that spend most of their time at that speed. NASCAR has experimented with paint texture and find smooth is better. Even the thickness of a decal will cause separation.
The drag on F1 cars is awfull and downforce requirements only adds to this problem. To get more lift with less drag is to minimise B/L separation. Various methods of energising boundry are employed. Once again different methods are used on race cars compared to airplanes.The votex generators on upper surfaces of aircraft wings are for sub sonic airfoils at high angle of attacks. IE, early Lears(25 and 35) had so little thrust that it was impossible to hand fly the airplane at its service ceiling. The A of A indicator showed the wing almost critical and with 10% of its generators missing, the wing would stall. Little holes in surfaces subject to separation on some military aircraft at slow speeds, created low pressure from turbine bleed off. Holes on leading edges were high pressure bleeds for deicing. The generators found on Lears are not effective at F1 speeds in such dense air.
The splitters on F1 cars are for very different reasons than splitters on supersonic aircraft. Because of so many unaerodynamic things sticking into the wind causing much turbulence on surrounding surfaces, their use is for simply sparating turbulent air far from the boundery layer and tidying up vortices before entering other important areas. (Sidepods etc.)
Some discoveries with smart paint ( changes color with pressure) in wind tunnel analysis, showed that in some areas aft of leading edges, orange peel paint surfaces reduced temperatures and extended the boundery layer. This was not the intended use of the paint as it was meant to analyse shapes. It seems air shearing in pockets narrowed the B/Layer. Sorry about the length.
Originally posted by TazioN
Yeah, but the vast majority of commercial airliners were designed and built years ago. Even newer planes are built in a way that minimizes costs and simplifies manteinance, and arguably, smooth metal body panels help achieve that. If that was not the case, they would be using a lot more carbon fiber and composites in commercial planes. I was talking about fighter jets and other applications where cost is not as important as performance gains.
The article I read was about fighter jets being designed now to enter service in a few years (one of the planes mentioned was the Joint Strike Fighter). If those guys say there's an aerodynamic advantage in texturing the skin of the plane in some way , I believe it.
#7
TazioN
-
- 312 posts
- Joined: August 01
Member
Posted 12 December 2001 - 04:22
Brian, that was really interesting. Thanks. I'd love to see a video of the windtunnel testing with that paint.
#8
KenC
-
- 2,254 posts
- Joined: August 01
Member
Posted 12 December 2001 - 04:52
Originally posted by TazioN
Brian, that was really interesting. Thanks. I'd love to see a video of the windtunnel testing with that paint.
I believe the Super Speedway IMAX DVD has a section showing the Reynard windtunnel with a CART model using this paint.
#9
Yelnats
-
- 2,026 posts
- Joined: May 99
Member
Posted 14 December 2001 - 15:04
Pressure Sensitive Paint has a future in F1 now that it has been optimised for low speed results by Ford. Until recently it was only effective at high sub-mach speeds but in the spring of 2000 Ford USA developed a low speed application of this technology that can respond to pressures generated at automotive speeds and is using it in their investigations for commercial automobile design. Can F1 be far behind?
Note the excellent co-relation of the bottom half of the CFD generated image with the PSP generated top section.
Note the excellent co-relation of the bottom half of the CFD generated image with the PSP generated top section.
#10
Colin
-
- 153 posts
- Joined: December 01
Member
Posted 22 December 2001 - 06:13
This may have already been posted on the other thread that was linked here, dimples work on a golf ball by causing the flow to transition from laminar (smooth) to turbulent, quickly. Since turbulent flow is more resistant to separation, this causes the air to remain attached to the golf ball longer and the drag to be lower since the ball produces less of a wake. However, since turbulent flow produces more drag than laminar flow, it's not good to just apply dimples to any 'ol shape and expect less drag. For the size and speed of a golf ball (i.e. for a golf ball's Reynold's number), the decreased separation reduces more drag than the trasition to turbulent flow adds, but for a larger, slower moving sphere this wouldn't be the case. (Dimples also create lift on a golf ball if it has backspin, or cause it to hook or slice if it is spinning on an axis not parallel to the ground)
How does this apply to an F1 car? I'm glad you asked. At the Re # of an F1 car, there will be very little laminar flow, likely only on the nose, the leading edge of other bodywork, and on the front half of the upper surface of wings. Therefore, there would be no advantage in adding dimples to trip flow to turbulent, since the flow will be turbulent already. Dimples will only add drag due to the disturbance in surface smoothness.
One thing not mentioned in this thread is a couple methods to reduce drag using surface texture. The first is taken from experiments on sharkskin in water, which in a certain orientation produces less drag than a flat, smooth surface of the same shape. On a microscopic level, sharkskin has tiny V-grooves that, when aligned parallel to the direction of the flow, act to delay the transition to turblent flow by delaying the increase in boundary layer thickness, although I'm not sure how it does this exactly. You can find more in the book The Leading Edge, about low-drag aerodynamics. 3M has used this concept to manufacture plastic sheets with the same type of tiny V-grooves. However, these tiny grooves have evolved on a shark to be parallel to the flow pattern over a shark's body, but in real life, on a complex 3D shape like an F1 car, you would have to be certain of the exact flow direction of the boundary layer to make this useful. If the flow direction is different than the orientation of the grooves, flow would cross laterally over them, adding more drag than a smooth surface.
The second method somewhat related to surface texture: you can use thousands of tiny holes on a surface, with a low pressure beneath it, to suck the boundary layer down and promote laminar flow. However, unless the low pressure beneath the surface were created through the basic aero-shape of the car, it would require a pump, which would be banned as "active aerodynamics". Other ways to achieve the same thing would be with tangential blowing of air across the surface or using a speaker to vibrate air in the same way. Joseph Katz has used speakers to enhance to lower the drag of a wing by 30% at the same downforce level. Too bad it is banned.
How does this apply to an F1 car? I'm glad you asked. At the Re # of an F1 car, there will be very little laminar flow, likely only on the nose, the leading edge of other bodywork, and on the front half of the upper surface of wings. Therefore, there would be no advantage in adding dimples to trip flow to turbulent, since the flow will be turbulent already. Dimples will only add drag due to the disturbance in surface smoothness.
One thing not mentioned in this thread is a couple methods to reduce drag using surface texture. The first is taken from experiments on sharkskin in water, which in a certain orientation produces less drag than a flat, smooth surface of the same shape. On a microscopic level, sharkskin has tiny V-grooves that, when aligned parallel to the direction of the flow, act to delay the transition to turblent flow by delaying the increase in boundary layer thickness, although I'm not sure how it does this exactly. You can find more in the book The Leading Edge, about low-drag aerodynamics. 3M has used this concept to manufacture plastic sheets with the same type of tiny V-grooves. However, these tiny grooves have evolved on a shark to be parallel to the flow pattern over a shark's body, but in real life, on a complex 3D shape like an F1 car, you would have to be certain of the exact flow direction of the boundary layer to make this useful. If the flow direction is different than the orientation of the grooves, flow would cross laterally over them, adding more drag than a smooth surface.
The second method somewhat related to surface texture: you can use thousands of tiny holes on a surface, with a low pressure beneath it, to suck the boundary layer down and promote laminar flow. However, unless the low pressure beneath the surface were created through the basic aero-shape of the car, it would require a pump, which would be banned as "active aerodynamics". Other ways to achieve the same thing would be with tangential blowing of air across the surface or using a speaker to vibrate air in the same way. Joseph Katz has used speakers to enhance to lower the drag of a wing by 30% at the same downforce level. Too bad it is banned.
#11
Yelnats
-
- 2,026 posts
- Joined: May 99
Member
Posted 22 December 2001 - 17:12
Very interesting and informative post, Colin! I would like to clarify one point. We have to be careful when relating hydrodynamics to F1 because of the vastly different properties of the two media involved. Air being 800 time less dense and compressible acts very differently than water so the surface properites of sharkskin are inaplicable to F1 applications due to scaling factors and surface drag characteristics.
One doesn't need to get into the details of Renolds numbers ect. to realise this as we only have to compare the hull of a ship and the topside to understand the magnitude of the differences.
One doesn't need to get into the details of Renolds numbers ect. to realise this as we only have to compare the hull of a ship and the topside to understand the magnitude of the differences.
#12
Colin
-
- 153 posts
- Joined: December 01
Member
Posted 24 December 2001 - 03:37
Good point, Yelnats, I neglected to point out the difference between the two mediums of air and water. The size of the grooves in the 3M product are actually optimized to work in air, but possibly with F1 cars it would not matter; it is very hard to keep flow from becoming turbulent at those high speeds.
