2022 cars 'porpoising' at high speed

[vorticism]

The clue is in the name: Pilot Induced Oscillation. The pilot creates the problem by over controlling and then exacerbates it by adding control inputs that are too late and thus cause an increasing change in attitude in a positive feedback loop. The aircraft doesn't do this inherently (except where the aircraft is deliberately unstable and the control laws aren't correctly implemented) - it's caused by the pilot. Hence Pilot Induced .

Thanks for the bold text, that really helps explain things. I hadn't read the first two thirds of the term PIO yet before. Fourth time: human agency isn't why I posted it here. The pilot doesn't write physics on his way toward the runway. Move-y thing with person inside goes very fast close to ground whilst having wobbly parts, whilst relying on lift.

[tpe]

Teams and driver this year are trying to avoid this:

[mzso]

Actually, I think a solution to some of this would be the banned tuned mass damper. This is how skyscrapers deal with vortex shedding induced resonance.

But how would that effect increasing downforce until it stalls, touches ground?

In all seriousness would a TMD or inerter have prevent this?! F1 can make itself look really stupid sometimes.

Why was the inerter banned anyway?
Would it even have effect is the porpoising that much different from normal suspension movement on bumps? Is it different at all?

[mzso]

I'm going to assume they won't suddenly allow active suspensions, but wouldn't the not long ago banned FRIC aid with the porpoising issue?

[mzso]

Apparently no one likes my bump-stop theory?

Wouldn't that be a tad problematic if you actually need the suspension at high speed, like any sort of bump?

[mzso]

So raise the ride height of the car then?

So just raise the height of the car until it doesn't bottom out at top speed and/or road compression: 50mm or 80mm static ride height (or whatever height is required) would do the trick, no...?

Better the teams do it of their own initiative, before the FIA step back in with the infamous laser beam and minimum static ride height of 60mm from the 1983 season!

Just no. The engineers should fix it using the tools available within the regulations, which is raising the car. If they are stubborn and refuse to do that, then a minimum static ride height of 60mm or whichever height, will be forced upon them perhaps...

I'm sure there will be a rush to do that, and watch other teams who didn't win...

As a regulator you WANT the cars to be choppy and to oscillate (in a safe way during corners or over serrated kerbs). It makes for a better spectacle and better engineering challenge, than overly sophisticated cars with a smooth, stable aero platform.

Even worse would be active suspension, talk about killing the spectacle...

I fail to see how a car swaying this way or that is a spectacle, or why should be a desire to keep it that way...

[mzso]

Someone on F1 Technical Reddit (is that affiliated with this site?) demonstrated how porpoising happens with a spoon and hairdryer:

https://www.reddit.com/r/F1Technical/co ... orpoising/

Is it the same though? Would the spoon porpoise if the handle was cut off?

Sent from my SM-G9910 using Tapatalk

Makes no sense. The weight of the handle what keeps it at a distance from the table, instead of a spring. The airflow pulls it down, which creates porpoising.

[djos]

Apparently no one likes my bump-stop theory?

Wouldn't that be a tad problematic if you actually need the suspension at high speed, like any sort of bump?

They are small progressive rate springs and other racing series use then this way.

[Hoffman900]

Actually, I think a solution to some of this would be the banned tuned mass damper. This is how skyscrapers deal with vortex shedding induced resonance.

But how would that effect increasing downforce until it stalls, touches ground?

Because that assumes that is actually yhe issue. Other than pundits, no one has said that is in fact what is happening and others have suggested it is what I said.

[Greg Locock]

Apparently no one likes my bump-stop theory?

Not much, because it's the tire sidewalls that dominate in the compliance stack, so changing the suspension is relatively small beer. It might work, but its really an aerolastic problem, an aerodynamic solution will treat the root cause, everything else is a bodge. Newey's book describes the same issue at Leyton House.

Imagine a venturi hinged at the rear axle, riding on a spring at the front. The ground comes up (or the front spring compresses due to braking etc, the venturi gap closes, the venturi creates more downforce, sucking the spring down even more, and then the flow chokes or stalls, stops developing as much downforce, the spring extends, the flow sorts itself out again, downforce builds, and here we go again. The fundamental issue with F1 suspension is that the tire vertical compliance is essentially undamped.

The test would be whether it is at the wheelhop frequency, related to the front axle weight and radial rate of the tires.

[djos]

Cheers, that makes a lot of sense.

[Greg Locock]

Thanks. I'm very wary of using the term 'choked' in relation to vehicle aero, as it specifically means creation of a Mach shockwave, and I doubt that is happening, the speeds are not enough. In engines you can see compressibility effects starting at flow speeds around 400 kph, where local velocities in the airstream going round bends might get up towards the transonic speeds. That's why powerful engines have big valves, but the radii under the floor are very large compared with engine intake and exhaust manifolds.

[Hoffman900]

Thanks. I'm very wary of using the term 'choked' in relation to vehicle aero, as it specifically means creation of a Mach shockwave, and I doubt that is happening, the speeds are not enough. In engines you can see compressibility effects starting at flow speeds around 400 kph, where local velocities in the airstream going round bends might get up towards the transonic speeds. That's why powerful engines have big valves.

Not quite. Pumping losses exceed mass flow gains at around .6 Mach in a port.

The valve isn’t always the minimum cross sectional area in a port, and only the exhaust would experience sonic conditions at low valve lifts.

The best example of sonic choking are sonic inlet restrictors which are found in many race classes https://www.raetech.com/Restrictors/Res ... nction.php

[Greg Locock]

measurable != dominant.

[henry]

Actually, I think a solution to some of this would be the banned tuned mass damper. This is how skyscrapers deal with vortex shedding induced resonance.

But how would that effect increasing downforce until it stalls, touches ground?

In all seriousness would a TMD or inerter have prevent this?! F1 can make itself look really stupid sometimes.

Why was the inerter banned anyway?
Would it even have effect is the porpoising that much different from normal suspension movement on bumps? Is it different at all?

Here’s a layman’s understanding of the inerter, I’m happy to be corrected by the more knowledgable members.

The inerter is a device with a small mass, say 3k, that acts in the suspension like a large mass, say 600kg, it’s inerrancy. So it provides opposing forces to movement based on the acceleration between its attachment points. By opposing the movement it damps it. This is in contrast to the conventional damper which provides a force proportional to the velocity between its attachment points.

The inerter acts as a store of energy, rather like the spring, and so when movement direction reverses the suspension has to remove energy from the inerter.

I believe that by suitable choice of inertance, motion ratios etc. in conjunction with the Springs and dampers it is possible to manage the displacement of the poorly damped tyre response. It’s a very long time since I did any of that stuff so I’ll just accept what the technical papers say.

The regulations also ban acceleration based valving in the conventional dampers.