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Unread 28 November 17, 14:35   #1
snookey
 
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Lightbulb Slip streaming away

It is the end of 2017 and there is still a airo problem with cars eliminating slip streaming. As soon as you get inside 3 feet of the car in front the car slides.
This is a problem that has been around the last 20 years.

And Ron Denis and his so called technical working group. Who where supposed to study the car in the wind tunnel and help generate rules to eliminate the problem. It is relay the technical not working group.
My buddy said Ron was getting money under the table by the FIA which could be true.

Put me in a wind tunnel with 2 full scale models 3 feet apart and i will tell you what is wrong. And then Libertey media can work on modifying the model to fix it. And make regulations to force teams to come up with something like it.
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Unread 6 December 17, 02:11   #2
MarioAndretti
 
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You don't need a wind tunnel to know what's wrong.It's called areo push and it's been around a lot longer than 20 years.Any and every car that depends on aerodynamic downforce to increase corner speed will have this issue.Wings don't work without clean air flowing over them.Because of this fact the car in front will always be faster through the turns.

So,how do you fix this problem?The only way to do so is to do away with the wings all together and force them to find speed through suspension tuning.The best setup and driver combination will be the fastest and the car won't care if it's in clean air or not.Just like the good old days.

Sure,the cars won't be as fast and might not look very good but you can't have it both ways.
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Unread 6 December 17, 04:07   #3
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Originally Posted by MarioAndretti View Post
...
Sure,the cars won't be as fast and might not look very good ....
The first is arguable, the second quite subjective.

F1 Monza 1971:
"This race featured the closest finish in Formula One history, as Peter Gethin beat Ronnie Peterson by 0.01 seconds. The top five were covered by just 0.61 seconds.... With an average speed of 242.615 km/h (150.754 mph), this race stood as the fastest-ever Formula One race for 32 years, until the 2003 Italian Grand Prix at Monza."

To these rheumy old eyes, modern F1 cars are almost as ugly as modern "Indycars", removing their wings wouldn't appreciably add or subtract from that. And yet they are more attractive than a few years ago, when they looked like insects. For both series I prefer the appearance of the early seventies - wings were established, though not huge, but sidepods had yet to appear.
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Unread 6 December 17, 06:36   #4
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There must be some way to do it. Look at Formula 4 / Formula Renault, they have wings, but can follow nose to tail with no problem. Perhaps the wings should be scaled back, the ground effects increased, and tires given more grip.
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Unread 6 December 17, 07:32   #5
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Quote:
Originally Posted by jgf View Post
The first is arguable, the second quite subjective.

F1 Monza 1971:
"This race featured the closest finish in Formula One history, as Peter Gethin beat Ronnie Peterson by 0.01 seconds. The top five were covered by just 0.61 seconds.... With an average speed of 242.615 km/h (150.754 mph), this race stood as the fastest-ever Formula One race for 32 years, until the 2003 Italian Grand Prix at Monza."

To these rheumy old eyes, modern F1 cars are almost as ugly as modern "Indycars", removing their wings wouldn't appreciably add or subtract from that. And yet they are more attractive than a few years ago, when they looked like insects. For both series I prefer the appearance of the early seventies - wings were established, though not huge, but sidepods had yet to appear.
Bit of a selective choice to pick a race at the one circuit which mostly consists of long straights (the fact that, out of the 25 races with the highest average speed, 23 of those were at Monza, shows that it is really a reflection of the fact that Monza is a bit of a freak circuit).

Round a circuit which has more than a few corners, you would notice a much larger difference - Willem Toet, the former Technical Director at Sauber, has modelled what the performance of a car with effectively no downforce would be, and the answer is quite slow - he used the Circuit de Catalunya as a base line, and his simulations indicated that the lap times would rise into the 1m40's (and slower than a Formula 3 car as a result).

MickeyMouse, I do not mean to pick on you for this, but the loose use of the term of "ground effects" really does frustrate me at times. The current cars do still utilise ground effects - the front wing assemblies use ground effects, and the floor of the car is also in ground effect as well. I know that Frank Dernie (who, having designed cars such as the FW07, knows a fair bit on this topic) has been rather publicly exasperated that fans seem to treat "ground effects" as if it is a magic wand that would make everything wonderful.

In fact, this thread is showing up some of the common fallacies that occur, as in this instance it's clear that everybody is instantly going on about the wings. However, the research that has been done shows that the wings aren't the problem - although they are effected, because the front and rear wings tend to lose the same amount of performance, the overall handling balance of the car remains similar and the trailing driver can adapt.

If anything, what was causing the problem was that the floor of the car was stalling and losing performance - not only did that result in a larger loss in performance (for all the focus on the upper bodywork, the underfloor area is still one of the most powerful aero surfaces), it also caused erratic shifts in handling that made it harder for the trailing driver to cope.

No doubt, though, that all we will get is the usual moaning of "take the wings off" or "use ground effects" again and again and again...
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Unread 6 December 17, 13:10   #6
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Quote:
Originally Posted by skiffle View Post
MickeyMouse, I do not mean to pick on you for this, but the loose use of the term of "ground effects" really does frustrate me at times. The current cars do still utilise ground effects - the front wing assemblies use ground effects, and the floor of the car is also in ground effect as well. I know that Frank Dernie (who, having designed cars such as the FW07, knows a fair bit on this topic) has been rather publicly exasperated that fans seem to treat "ground effects" as if it is a magic wand that would make everything wonderful.
I'm well aware of ground effects, indeed, a majority of total downforce is from the underbody aerodynamics, not the wings. But, the wings seem to be the main problem when following a car. The common opinion seems to be that the underbody is not nearly as sensitive to turbulence as the wings are (the ground reduces the turbulent kinetic energy and slows the air faster than the freestream flow field). As was pointed out, aero-push gets worse as you get closer. This is externally apparent from cars frequently running wide and locking wheels while following at 0.5s or less. You can largely solve this by just increasing the front downforce, but then you get too much drag and can't get the top speed to try for a pass in the first place, so it's a catch-22 situation.

The two main factors of loss of downforce are turbulence and relative freestream velocity. Basically, the car ahead drags a mass of air along with it, reducing the relative freestream velocity of the car behind. This is analogous to a plane wanting to land into the wind instead of with it to reduce ground speed but still have the same airspeed. As far as I've read, the underbody aerodynamics are not as sensitive to turbulence nor relative velocity as the wings are, so presumably reducing the dependence somewhat on wings, and increasing it proportionately in the underbody could help. If this is true, the question then is if the effect is big enough to significantly improve the racing. Cars start to have issues at 1-1.2 seconds back, so more drastic changes may be needed.

Quote:
Originally Posted by skiffle View Post
In fact, this thread is showing up some of the common fallacies that occur, as in this instance it's clear that everybody is instantly going on about the wings. However, the research that has been done shows that the wings aren't the problem - although they are effected, because the front and rear wings tend to lose the same amount of performance, the overall handling balance of the car remains similar and the trailing driver can adapt.
I've never read that theory before, sounds interesting (and counter to nearly all driver comments), do you have a source we can read?
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Unread 6 December 17, 17:46   #7
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It's not just F1 cars either. GT3 cars are pretty aero dependent and can have issues.

The Pirelli World Challenge broadcast team brought this up at Road America about the overtaking issues there. No one could overtake into turn 12 (Canada) because they couldn't follow the next car closely enough through the Kink due to "aero push", especially when following the big Bentley
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Unread 7 December 17, 03:13   #8
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Originally Posted by MickeyMouse View Post
There must be some way to do it. Look at Formula 4 / Formula Renault, they have wings, but can follow nose to tail with no problem. Perhaps the wings should be scaled back, the ground effects increased, and tires given more grip.
F1 technology has gotten so specific, so finely tuned, that it doesn't take much to step outside the parameters and upset the car's handling/balance. It would not be that difficult to redesign the suspension so mechanical grip is paramount, and with a broader "optimum" range, and aero influence scaled back, then you would have cars less affected by airflow so capable of more maneuvering, thus more racing.

Ground effects are just as finicky. As long as the airflow is perfectly longitudinal the handling is predictable, but let the car get even a little out of line, if the airflow is even 20deg off, and the downforce rapidly diminishes. CART cars of the early to mid nineties had such ground effects that they could have run upside down on a ceiling, and drivers frequently commented that if you got the least bit sideways it was like hitting a patch of ice.

All these high tech innovations are fascinating for us technophiles, and they create faster cars, quicker cars, better handling cars ...at the expense of versatile cars. That F1 car will give a phenomenal performance on the track by itself, but surround it with a dozen other cars, with varying environmental conditions (wind, temperature, humidity, track surface, etc.), and suddenly nothing is optimal anymore because the design parameters are too narrowly specified.
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Unread 10 December 17, 20:25   #9
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Quote:
Originally Posted by MickeyMouse View Post
I'm well aware of ground effects, indeed, a majority of total downforce is from the underbody aerodynamics, not the wings. But, the wings seem to be the main problem when following a car. The common opinion seems to be that the underbody is not nearly as sensitive to turbulence as the wings are (the ground reduces the turbulent kinetic energy and slows the air faster than the freestream flow field). As was pointed out, aero-push gets worse as you get closer. This is externally apparent from cars frequently running wide and locking wheels while following at 0.5s or less. You can largely solve this by just increasing the front downforce, but then you get too much drag and can't get the top speed to try for a pass in the first place, so it's a catch-22 situation.
I appreciate that my initial post was a bit sharp, but it is because quite often there seems to be quite a few misconceived ideas about ground effects.

One of those points is the concept that "ground effects are relatively insensitive to turbulent air", which is not necessarily the case. Willem Toet has produced some good discussions on the nature of diffusers in motorsport, and pointed out that the current regulations in F1 have promoted the use of diffusers with a relatively high expansion ratio.

That has actually lead to a shift towards a slightly increased proportion of the total downforce being produced by the car, but can also lead to localised flow separation near the mouth of the diffuser. In the turbulent wake of another car, you can have increased flow separation near the mouth of the diffuser and partial stalling of the diffuser - not only resulting in a much more pronounced drop in downforce, but also resulting in a marked rearward shift in the handling balance (since now the peak drop in pressure beneath the floor would be shifting rearward).

The phenomenon that you describe and term as "aero push" would be explainable by that same mechanism - that it is not necessarily just the total loss of downforce that is the issue, but the fact that the centre of pressure and therefore the overall handling balance has shifted rearwards.

Equally, it has been pointed out that the front wings of the current F1 cars are also working in ground effect - and, in some instances, almost share more performance characteristics with the front diffusers of a Le Mans Prototype car than with a conventional wing, although not as extreme as some series (the Honda aero kits for their IndyCars in recent years comes to mind, where the front wing was much more like a small front diffuser).

With regards to the impact on the handling balance, I shall have to see if I can find the discussion on the F1Technical forums where it came up - there was a researcher who had produced a series of papers on the phenomenon.

I think that part of the problem was that the drivers were perceiving the loss in downforce and ascribing it to the wings because that is the main visible aero surface, but in that sense their opinion was not that much more informed - they perceived the effects, but not necessarily understood the cause.
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Unread Yesterday, 05:39   #10
MickeyMouse
 
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Quote:
Originally Posted by skiffle View Post
That has actually lead to a shift towards a slightly increased proportion of the total downforce being produced by the car, but can also lead to localised flow separation near the mouth of the diffuser. In the turbulent wake of another car, you can have increased flow separation near the mouth of the diffuser and partial stalling of the diffuser - not only resulting in a much more pronounced drop in downforce, but also resulting in a marked rearward shift in the handling balance (since now the peak drop in pressure beneath the floor would be shifting rearward).
Interesting. If that's the main problem wouldn't it be a pretty simple fix by just changing the
diffuser rules to force a greater stall margin?
I'm a little surprised a diffuser stall would shift the CP rearward, I was under the impression that a diffuser stall would increase the rear pressure and shift the CP forward, or is it a case that once the diffuser stalls the wings create a greater portion of the total downforce, and the rear wing creates more downforce than the front wing shifting the CP rearward?
I wonder if allowing some form of limited blown diffuser to re-energize the boundary layer and delay flow separation at the diffuser mouth would improve trailing car performance.

Quote:
Originally Posted by skiffle View Post
Equally, it has been pointed out that the front wings of the current F1 cars are also working in ground effect - and, in some instances, almost share more performance characteristics with the front diffusers of a Le Mans Prototype car than with a conventional wing, although not as extreme as some series (the Honda aero kits for their IndyCars in recent years comes to mind, where the front wing was much more like a small front diffuser).
True, but I'm not sure if the passing in 2005-2008 with the high front wings was noticeably different. In 2009 they went back to the low flat wings, but with moveable flaps. High wings should be investigated again if they could improve draft performance (aesthetically they are pretty bad however).
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