2022 cars 'porpoising' at high speed

[Hoffman900]

The floor touching the asphalt is what causes the venturi to choke, which triggers the porpoising. You cannot porpoise without first contacting the asphalt.

Not true. Vortex shedding can cause it as well, especially if the car is resonating at the same frequency of the now required mechanical springs or causing wing supports to flutter on some small level.

In my little world, we were joking about running a shaker rig in the wind tunnel, but it's not going to tell you much with the rules required 60% model.

Interesting. Thanks for the clarification. The vortex shedding frequency sounds like a fk'd aero concept. I believe the old Audi R18s suffered from this in the '14 or '15 Spa weekend.

It could be, also it's hard to impossible to model. My Phd friend's opinion is they should have opened up more on track testing this year, away from prying eyes, as relying on less real world testing and limiting design time (and creating an over reliance on simulations), this was inevitable.

[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.

[Rodak]

In my little world, we were joking about running a shaker rig in the wind tunnel, but it's not going to tell you much with the rules required 60% model.

That would be tough with a rolling floor!

[Hoffman900]

In my little world, we were joking about running a shaker rig in the wind tunnel, but it's not going to tell you much with the rules required 60% model.

That would be tough with a rolling floor!

That’s one of the many issues, and it’s near impossible to model (and that would still just be an approximation).

Most cfd models are done as an infinitely stiff model, and that’s not reality, or is resonance induced by aero and the car traveling down the road.

[Chuckjr]

If the floor is not touching the asphalt, bouncing like this is decent

The floor touching the asphalt is what causes the venturi to choke, which triggers the porpoising. You cannot porpoise without first contacting the asphalt.

Not true. Vortex shedding can cause it as well, especially if the car is resonating at the same frequency of the now required mechanical springs or causing wing supports to flutter on some small level.

In my little world, we were joking about running a shaker rig in the wind tunnel, but it's not going to tell you much with the rules required 60% model.

That is amazing information. Thank you for sharing.

If this porpoising becomes a fundamental issue nearly across the board, do you think the FIA would allow electronic suspension systems to instantly solve this instead of admitting to causing yet another debacle (should it become one), and forcing a rethink of the whole concept? The 2014 engine regs would be the last FIA regs fail that comes to mind.

I understand the teams likely will fix this, but in the off chance they can’t because it’s fundamentally a flawed design...

This situation reminds me of the Grumman x29, a plane so unstable fundamentally it required a computer to remain stable.

[Hoffman900]

My non professional guess is they shouldn’t have changed the suspension rules and the aero concept at the same time, and opened up testing this year.

I suspect the teams will get a handle on it, but it will be a compromise, but in the same way NASCAR teams had to compromise on the much ill fated Car of Tomorrow, which NASCAR was hell bent on not repeating with the Gen7.

I do personally know of a chassis that went into resonance for an amateur team on a shaker rig. That was a mechanical design / stiffness / weight balance issue, but it is possible. Apparently it almost bounced off the machine.

[Hoffman900]

The floor touching the asphalt is what causes the venturi to choke, which triggers the porpoising. You cannot porpoise without first contacting the asphalt.

Not true. Vortex shedding can cause it as well, especially if the car is resonating at the same frequency of the now required mechanical springs or causing wing supports to flutter on some small level.

In my little world, we were joking about running a shaker rig in the wind tunnel, but it's not going to tell you much with the rules required 60% model.

That is amazing information. Thank you for sharing.

If this porpoising becomes a fundamental issue nearly across the board, do you think the FIA would allow electronic suspension systems to instantly solve this instead of admitting to causing yet another debacle (should it become one), and forcing a rethink of the whole concept? The 2014 engine regs would be the last FIA regs fail that comes to mind.

I understand the teams likely will fix this, but in the off chance they can’t because it’s fundamentally a flawed design...

This situation reminds me of the Grumman x29, a plane so unstable fundamentally it required a computer to remain stable.

This is actually a lot of aircraft now, x plane and commercial (see the 737Max).

[sunny1304r]

This is how it looks like on 20222 cars:

[Zynerji]

I've run into this back in the rFactor sim days. It was actually solved with the 3rd springs in that scenario. So, the front bound setting was maxxed (or near max), and the rear rebound raised until it stopped the porpoise (tiny steps to find).

Kinematically, I have no idea why that worked, but that was the solution after brute testing micro-changes for several hours.

[Hoffman900]

I think they should bring back the hydraulic heave spring to start.

It looks like a low rider

But in all seriousness, that is untenable for the driver for 2 hours.

[Hoffman900]

I've run into this back in the rFactor sim days. It was actually solved with the 3rd springs in that scenario. So, the front bound setting was maxxed (or near max), and the rear rebound raised until it stopped the porpoise (tiny steps to find).

Kinematically, I have no idea why that worked, but that was the solution after brute testing micro-changes for several hours.

It worked in the game, but don’t read too much into rFactor.

We raced a Datsun 510 once that did this going down the straight. It sat on the bump stops in the rear. It was obnoxious and unstable. Some people shouldn’t be allowed to build their own race cars.

Edit: from a competitor’s car (we have the black TR4 in the lead) 5:44 https://onedrive.live.com/?authkey=%21A ... 11&o=OneUp

[godlameroso]

Rebound would limit extension heave. If it's an aero phenomena, I'd look at the plank area, I imagine the stalling that happens there, propagates to the rest of the floor. The strake placement affects the plank area pressure distribution as well. Maybe they should look to boat bows, and how they deal with bow shocks.

[Just_a_fan]

If this porpoising becomes a fundamental issue nearly across the board, do you think the FIA would allow electronic suspension systems to instantly solve this instead of admitting to causing yet another debacle (should it become one), and forcing a rethink of the whole concept? The 2014 engine regs would be the last FIA regs fail that comes to mind.

An inverter or TMD would be simpler than an electronic system.

This situation reminds me of the Grumman x29, a plane so unstable fundamentally it required a computer to remain stable.

The X29 was the most aerodynamically unstable built, according to DARPA, but others had preceeded it down this route, notably such as the F16.

The Wright brothers built their flyer with intentionally relaxed stability thanks to an anhedral design, so the idea of a not-fully-stable design goes right back to day 1, interestingly.

[Just_a_fan]

I think they should bring back the hydraulic heave spring to start.

It looks like a low rider

But in all seriousness, that is untenable for the driver for 2 hours.

The simplest way to prevent the oscillations is to raise the ride height slightly.

[Jolle]

Could it be, that it’s finding the balance? You need (all relative of course) a stiff suspension setup for ground effect but a loose one for low speed corner grip. More a case of how soft can you go without bumping off track? (Especially with the stiffer tires)
Should be a lot of dancing cars through Monaco this year…