Problems for Mclaren with development

[CHT]

Mclaren is definitely struggling at the moment. according to ITV, the new MP4-24 rear wing is stalling and that sounds like a big aero design problem which they might not be able to fix without redesigning the front.

As for development of the new car, I believe by having a more experience driver who is strong in development this season will always help due to the drastic change to this year's car. Maybe thats the reason why BGP prefer to keep Ruben instead of having a rookie.

Having a test driver like Pedro will help, but he will still have to understand the car first (by driving it) before he can make any recommendation. And the test restriction is bad news for Mclaren right now.

Anyway, Mclaren still have a test session at Jerez next week, so its still possible that Mclaren will surprise everyone there.

[RacingManiac]

What teams did the new wind tunnel regulations (limiting scale to 60% and speed to 50 m/s) affect? Did McLaren (and possibly others)operate beyond these restrictions in the past? Might the new restrictions introduce some variability in the calibration that were unforseen?

For reference 50m/s is just over 100mph, now I don't know if scaling down a model to 60% of full size has an effect on the speed or not, but if not I'm pretty certain their wind tunnels would have been used above that speed.

Reynold's number would probably require the speed a lot faster than that for smaller scale....

[kilcoo316]

What teams did the new wind tunnel regulations (limiting scale to 60% and speed to 50 m/s) affect? Did McLaren (and possibly others)operate beyond these restrictions in the past? Might the new restrictions introduce some variability in the calibration that were unforseen?

For reference 50m/s is just over 100mph, now I don't know if scaling down a model to 60% of full size has an effect on the speed or not, but if not I'm pretty certain their wind tunnels would have been used above that speed.

Reynolds number, Re = (rho * V * L) / mu


(From full scale to 50%) L divides by a half, so at the same speed (V) the Reynolds number halves. To get back to the same Reynolds number, you'd need to multiply V by 2.

Re(transition) is approx 5x10^5 - and F1 cars operate in a virtually fully turbulent flow anyway. It'll not really be affecting laminar/turbulent transition - and even if it does, its not that important to an F1 car.



What it would influence is the ratio between viscous and turbulent mixing in eddies - and that is something that really would apply to F1 cars.

[xpensive]

For kilcoo;
When presenting formulas like the one above, I am rather certain that it would help a lot of people on this great forum if you would care to identify the parameters involved, preferably along with SI-units, don't you agree?

[dumbdave]

Reynolds number = ( Fluid Density (kg/m^3) * Fluid Velocity (m/s) * Characteristic length (m) ) / Dynamic Viscosity(N.s/m^2)

although it really is only a quick google away...

[xpensive]

Right, but how to define "Characteristic length (m)" in the case of an F1 car?
Kilcoo, are you there?

[noname]

Reynolds number is a dimensionless and does not depend on the unit system used for it calculation, as long as it is being used consistently.

also its (Re) definition is widely available, so every one interested can check it.

as for characteristic dimension in case of cars width is used quite often (when the whole car is concerned).

[xpensive]

Correct noname, but "dimensionless" does not necessarily mean that it will work with imperial units without the usual factors, check things out here:

http://en.wikipedia.org/wiki/Reynolds_number

The "characteristic dimension" is always interesting however, for example when we analyze hydraulic flows within thin-gap theory, we typically use the gap-thickness itself for this.

[kilcoo316]

Right, but how to define "Characteristic length (m)" in the case of an F1 car?

Kilcoo, are you there?

Is is the length along any surface. There is not one Reynolds number unique to an F1 car.

Reynolds number describes the induction of turbulence from previously laminar flow. The greater the viscosity, the longer along the part you can go before the flow trips to turbulence. The lower the air density = same effect.


But the Reynolds number works on laminar flow as an input. Within an F1 car, the freestream turbulence is very high - and varies significantly depending on what part of the car you are dealing with. Which somewhat (ok, very much) impacts the applicablity of the basic Re eqn here.


Obviously the rear wing support beam is operating in a much more turbulent environment than the front wing centre section.


In short, I would expect tunnel test conditions to have been tailored to what they were analysing - with matching in-tunnel to on-track conditions a very key element in which teams are at the sharp end, and which are not. Now, with the restrictions on tunnel tests... this will be harder to achieve.

[noname]

Correct noname, but "dimensionless" does not necessarily mean that it will work with imperial units without the usual factors (...)

that why I said "consistently", maybe I should add "correctly", also.
personally I do "like" them whenever I have to play with heat transfer or gravity.

btw, imperial units are never ending source of "fun" for their users.
guys from Ariane program know that very well

[xpensive]

Those guys who confused Nm and feet-lbs, missing Saturn with a hunded miles or so?

[myurr]

Mclaren is definitely struggling at the moment. according to ITV, the new MP4-24 rear wing is stalling and that sounds like a big aero design problem which they might not be able to fix without redesigning the front.

As for development of the new car, I believe by having a more experience driver who is strong in development this season will always help due to the drastic change to this year's car. Maybe thats the reason why BGP prefer to keep Ruben instead of having a rookie.

Having a test driver like Pedro will help, but he will still have to understand the car first (by driving it) before he can make any recommendation. And the test restriction is bad news for Mclaren right now.

Anyway, Mclaren still have a test session at Jerez next week, so its still possible that Mclaren will surprise everyone there.

If it's true that the rear wing is stalling then no manner of input from the driver is going to help fix that. That's a fundamental aero problem that can only be fixed by the boffins back at the factory.

[timbo]

Anybody else thinks that the root of the problems may lie not in the aero?
I heard that contrary to most teams they feed KERS from the rear end of engine. Maybe they have too much weight on the rear?

[Shaddock]

Anybody else thinks that the root of the problems may lie not in the aero?
I heard that contrary to most teams they feed KERS from the rear end of engine. Maybe they have too much weight on the rear?

If that is the case then the 'easy fix' would be to rip out KERS and turn up at the first 3 races with a faster overall package, tyres that will last and improved reliability. Easy win for McLaren.

I'm of the opinion that it's aero related unfortunately. They tend to be harder to fix.

[twoshots]

I believe the McL KERS is linked in at the front, not the rear.