Evolution of Aerodynamic Testing in F1

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Vyssion
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Evolution of Aerodynamic Testing in F1

Post by Vyssion » Fri Jun 01, 2018 2:30 pm

Image

Hi all again,

jjn9128 and myself have written a new article fr F1Technical on Wind Tunnels and how they are used in the world of Formula 1. The article touches on Wind Tunnels and their design, along with going into the models themselves and how they are moved, and finally touching on tyres.

Once again, if you have any questions, comments or feedback, this thread serves to facilitate that for everyone.

From myself and jjn9128, enjoy!!

https://www.f1technical.net/features/21646
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Dipesh1995
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Re: Evolution of Aerodynamic Testing in F1 - Windtunnels

Post by Dipesh1995 » Fri Jun 01, 2018 4:14 pm

Fantastic read guys =D>. One thing that caught my attention particularly was how do teams manage to steer the front wheels with a moving ground plane to simulate cornering?

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Re: Evolution of Aerodynamic Testing in F1 - Windtunnels

Post by jjn9128 » Fri Jun 01, 2018 5:05 pm

Dipesh1995 wrote:
Fri Jun 01, 2018 4:14 pm
Fantastic read guys =D>. One thing that caught my attention particularly was how do teams manage to steer the front wheels with a moving ground plane to simulate cornering?
Thank you.

The suspension is fully articulated, so there's a motor attached to the track rod. Yaw is quite small so the scrub isn't a major load into the balance but you would do a datum run, wind-off with the belt moving at ~1m/s, to remove the hysteresis from the measurements. (Subtract the datum forces from the wind-on measurements before non-dimensionalising)
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Tommy Cookers
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Re: Evolution of Aerodynamic Testing in F1 - Windtunnels

Post by Tommy Cookers » Fri Jun 01, 2018 5:25 pm

this area of activity and interest tends to be unclear about so-called yaw .....
we shouldn't have to wonder whether someone means yaw displacement, yaw velocity, or even yaw acceleration

iirc in aeronautic wind tunnel work Beta angle is the conventional term for displacement (in 'yaw')
and once yaw seemed to mean angular velocity (in 'yaw')

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Re: Evolution of Aerodynamic Testing in F1 - Windtunnels

Post by jjn9128 » Fri Jun 01, 2018 5:52 pm

Tommy Cookers wrote:
Fri Jun 01, 2018 5:25 pm
this area of activity and interest tends to be unclear about so-called yaw .....
we shouldn't have to wonder whether someone means yaw displacement, yaw velocity, or even yaw acceleration

iirc in aeronautic wind tunnel work Beta angle is the conventional term for displacement (in 'yaw')
and once yaw seemed to mean angular velocity (in 'yaw')
Yaw in this case is the angle between the model coordinate x-axis and the tunnel coordinate x-axis. Angular velocity in yaw (i.e. rotating around the z-axis) would be yaw rate no?
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Vyssion
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Re: Evolution of Aerodynamic Testing in F1 - Windtunnels

Post by Vyssion » Fri Jun 01, 2018 7:05 pm

jjn9128 wrote:
Fri Jun 01, 2018 5:52 pm
Tommy Cookers wrote:
Fri Jun 01, 2018 5:25 pm
this area of activity and interest tends to be unclear about so-called yaw .....
we shouldn't have to wonder whether someone means yaw displacement, yaw velocity, or even yaw acceleration

iirc in aeronautic wind tunnel work Beta angle is the conventional term for displacement (in 'yaw')
and once yaw seemed to mean angular velocity (in 'yaw')
Yaw in this case is the angle between the model coordinate x-axis and the tunnel coordinate x-axis. Angular velocity in yaw (i.e. rotating around the z-axis) would be yaw rate no?
To me, it was always this:

Yaw = Angular position away from the global x-axis (in this case) about the z-axis = akin to displacement kinda
Yaw Rate = Angular velocity of motion away from the global x-axis = akin to yaw velocity (basically the rate of change of velocity)
Yaw Acceleration was always stated as that in my work
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hardingfv32
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Re: Evolution of Aerodynamic Testing in F1 - Windtunnels

Post by hardingfv32 » Mon Jun 04, 2018 4:30 am

It was stated:

"As the RWTT limits teams to 60% scale models at 50m/s, the teams can only achieve dynamic similarity to the full-size car travelling at 108km/hr (67.5mi/hr)."

In simple terms does this mean that the current F1 60% tunnels represent a simulated max test speed of only 108km/hr?

Brian

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Re: Evolution of Aerodynamic Testing in F1 - Windtunnels

Post by jjn9128 » Mon Jun 04, 2018 8:27 am

hardingfv32 wrote:
Mon Jun 04, 2018 4:30 am
It was stated:

"As the RWTT limits teams to 60% scale models at 50m/s, the teams can only achieve dynamic similarity to the full-size car travelling at 108km/hr (67.5mi/hr)."

In simple terms does this mean that the current F1 60% tunnels represent a simulated max test speed of only 108km/hr?

Brian
Yes the model in the wind tunnel is simulating the car on the road at only 108km/hr.
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hardingfv32
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Re: Evolution of Aerodynamic Testing in F1 - Windtunnels

Post by hardingfv32 » Mon Jun 04, 2018 5:12 pm

Obviously current wind tunnel usage yields very useful data.

How is that possible with such low air flow speeds? What is the science of scaling up the data so that it a useful representation of 2x-3x high air flow speeds?

Brian

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Re: Evolution of Aerodynamic Testing in F1 - Windtunnels

Post by Vyssion » Mon Jun 04, 2018 5:30 pm

hardingfv32 wrote:
Mon Jun 04, 2018 5:12 pm
Obviously current wind tunnel usage yields very useful data.

How is that possible with such low air flow speeds? What is the science of scaling up the data so that it a useful representation of 2x-3x high air flow speeds?

Brian
Simplistically speaking, it comes down to matching similarity parameters which preserve similarity of viscosity and compressibility.

Reynolds Number is the similarity parameter for viscosity. It is defined as the ratio of the inertial forces (i.e. how resistant to some change in motion the flow is) vs. viscous forces (how sticky the flow is). You multiply the fluid density with its velocity and then some characteristic length (i.e. chord for a wing) and then divide all that by the flows viscosity coefficient. All the units cancel out and youre left with a dimensionless number. As you probably guessed, you can get this "constant" with any velocity and length you choose!! So if you are careful, you can scale up a wing x2 for example, and then as long as you 1/2 the velocity, you will obtain the same Reynolds Number. This means that you can treat the flows as somewhat identical. This is the easy part.

Where things get a bit tricky is that when you increase the velocity by enough (usually above 0.3x the speed of sound) air's compressible nature begins to have a fairly decent impact on the results. As your air moves over the part at lower speeds, the air is deflected and moved around the part. If your speed is above this ~0.3 Mach speed, then part of the energy that is in the flow is "lost" to being used to compress the air in regions where it first hits the goemetry (e.g. an aerofoils leading edge). Since there is a change in energy within the flow, thats where the tricky part comes in: measuring aerodynamic forces when there is a considerable amount of compressibility in either the scale or full-scale test will lead to different results if this similarity parameter isnt observed.

Manging both together is the tricky part since a decrease in scale leads to an increase in velocity in order to preserve Reynolds Number, which MAY lead to air exhibiting compressibility, which would influence your measured forces - making them less accurate. If Reynolds Number isn't kept constant, but Mach Number is, this can mean that the flow physics around a part aren't consistent, and yet again, give you incorrect results.
"And here you will stay, Gandalf the Grey, and rest from journeys. For I am Saruman the Wise, Saruman the Ring-maker, Saruman of Many Colours!"

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Re: Evolution of Aerodynamic Testing in F1 - Windtunnels

Post by Vanja #66 » Mon Jun 04, 2018 5:57 pm

It should be said that it's possible to match both Reynolds and Mach number to expected reality conditions (e.g. airliner cruise speed), but this usually means using different gas (not air) and/or dropping the temperature of the gas in wind tunnel. As far as I know, this is forbidden in F1, as it costs extra.
And they call it a stall. A STALL!

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Tommy Cookers
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Re: Evolution of Aerodynamic Testing in F1 - Windtunnels

Post by Tommy Cookers » Mon Jun 04, 2018 7:49 pm

the main method of increasing/matching the Reynolds number is raising the air pressure

presumably model structure stiffness ie multiple slotted flaps limits how far this can be done (nobody uses 17 bar today)
Re similarity is most important in low-speed flight configurations eg even fullsize Re Nos are possible for carrier approaches

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Re: Evolution of Aerodynamic Testing in F1 - Windtunnels

Post by godlameroso » Mon Jun 04, 2018 10:09 pm

Temperature affects Re# hard to simulate solar radiation on track in the tunnel, and the effect that has on aero.
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Re: Evolution of Aerodynamic Testing in F1

Post by turbof1 » Fri Jun 08, 2018 9:56 am

Title of the topic slightly updated to accomodate second article of "Evolution of Aerodynamic Testing in F1"
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Re: Evolution of Aerodynamic Testing in F1

Post by turbof1 » Fri Jun 08, 2018 11:32 am

#AeroFrodo