Mercedes W13

[dans79]

The porpoising is caused by alternate loss and gain of downforce occurring when the floor gets too close to the ground and when it gets back up respectively. The load generated by the upper part of the car does not suffer from this effect. The reason why we see this effect this year is that a way larger portion of the downforce comes from the floor.

It's coming from the suspension too. Undamped heave mode.

How is it 'coming from' the suspension? The suspension is moving as a consequence of the changing load under the car.
Its that severe change in the load that needs to be better controlled.

I think he might be inferring to a harmonic, between the suspension and the proposing!

[matteosc]

Yeah, so I am suggesting the proposing can be reduced if the teams design the upper part of the car to be a bit more on on the stable side.. as in less aggressive cambers on the wings so that slight displacements don't change the lift/drag too much.

The porpoising is caused by alternate loss and gain of downforce occurring when the floor gets too close to the ground and when it gets back up respectively. The load generated by the upper part of the car does not suffer from this effect. The reason why we see this effect this year is that a way larger portion of the downforce comes from the floor.

It's coming from the suspension too. Undamped heave mode.

It is not like a road bump, you cannot just damp it out. It is an oscillatory force, not an impulse: you may reduce the amplitude by increasing the damping (it does not necessary work, by the way), but you then have issues when hitting curbs and in general in optimizing the mechanical grip.

[NicoS]

And how is the rear of the car choking the throat on the Mercedes?

sidepods optimised for downwash, not directing enough flow over diffuser, lack of low pressure over diffuser, resulting in less effective evacuation of air from under car, thus chocking channels.

Not directing enough flow over the diffuser? Have you seen the sheer amount of exposed floor there is on this car?

does exposed floor = enough flow over top of diffuser?
What about beam wing design?

[matteosc]

It's coming from the suspension too. Undamped heave mode.

How is it 'coming from' the suspension? The suspension is moving as a consequence of the changing load under the car.
Its that severe change in the load that needs to be better controlled.

I think he might be inferring to a harmonic, between the suspension and the proposing!

Even if the problem was only that the frequency of the porpoising matches a natural frequency of the car, it would be very complicated to solve. You cannot change the mass or the mass distribution, so you would need to change the stiffness dramatically, affecting the behavior of the car from a mechanical standpoint.

[Just_a_fan]

Flow at the rear will effect flow at the front. it's not to isolated systems.
like a hose, you block the outlet, you choke the inlet, simple.

And how is the rear of the car choking the throat on the Mercedes?

sidepods optimised for downwash, not directing enough flow over diffuser, lack of low pressure over diffuser, resulting in less effective evacuation of air from under car, thus chocking channels.

Downwash brings air down and across the floor over the diffuser.

Diffuser isn't the issue as evidenced by the team cutting back turning vanes under the leading edge of the floor. They're struggling to get enough in to the floor, not out of it.

[NicoS]

And how is the rear of the car choking the throat on the Mercedes?

sidepods optimised for downwash, not directing enough flow over diffuser, lack of low pressure over diffuser, resulting in less effective evacuation of air from under car, thus chocking channels.

Downwash brings air down and across the floor over the diffuser.

Diffuser isn't the issue as evidenced by the team cutting back turning vanes under the leading edge of the floor. They're struggling to get enough in to the floor, not out of it.

Downwash can bring air down to side of floor, to seal, not necessarily to the rear. Mercedes will soon revert to normal sidepods to help guide air to rear of car.

[AR3-GP]

The porpoising is caused by alternate loss and gain of downforce occurring when the floor gets too close to the ground and when it gets back up respectively. The load generated by the upper part of the car does not suffer from this effect. The reason why we see this effect this year is that a way larger portion of the downforce comes from the floor.

It's coming from the suspension too. Undamped heave mode.

How is it 'coming from' the suspension? The suspension is moving as a consequence of the changing load under the car.
Its that severe change in the load that needs to be better controlled.

The suspension controls how quickly and how far the car rebounds upwards when the floor dies.

[AR3-GP]

The porpoising is caused by alternate loss and gain of downforce occurring when the floor gets too close to the ground and when it gets back up respectively. The load generated by the upper part of the car does not suffer from this effect. The reason why we see this effect this year is that a way larger portion of the downforce comes from the floor.

It's coming from the suspension too. Undamped heave mode.

It is not like a road bump, you cannot just damp it out. It is an oscillatory force, not an impulse: you may reduce the amplitude by increasing the damping (it does not necessary work, by the way), but you then have issues when hitting curbs and in general in optimizing the mechanical grip.

RB have a bit of pprpoising this weekend but the amplitude is tiny in comparison to the Mercedes.

[matteosc]

It's coming from the suspension too. Undamped heave mode.

It is not like a road bump, you cannot just damp it out. It is an oscillatory force, not an impulse: you may reduce the amplitude by increasing the damping (it does not necessary work, by the way), but you then have issues when hitting curbs and in general in optimizing the mechanical grip.

RB have a bit of pprpoising this weekend but the amplitude is tiny in comparison to the Mercedes.

Yes, I saw it, but that just means that they are able to better handle the issue. It may be for multiple reasons. Maybe RB is able to run higher without loosing too much downforce, maybe RB underfloor design is less prone to "choking" and causing porpoising, maybe they produce less downforce from the floor, maybe the downforce produced by the floor is more towards the front of the car and so on...
There are tons of reasons for which this is happening.

[PlatinumZealot]

Yeah, so I am suggesting the proposing can be reduced if the teams design the upper part of the car to be a bit more on on the stable side.. as in less aggressive cambers on the wings so that slight displacements don't change the lift/drag too much.

The porpoising is caused by alternate loss and gain of downforce occurring when the floor gets too close to the ground and when it gets back up respectively. The load generated by the upper part of the car does not suffer from this effect. The reason why we see this effect this year is that a way larger portion of the downforce comes from the floor.

I know this.. Just suggesting an easier way to mitigate in the time being.

[Mchamilton]

sidepods optimised for downwash, not directing enough flow over diffuser, lack of low pressure over diffuser, resulting in less effective evacuation of air from under car, thus chocking channels.

Not directing enough flow over the diffuser? Have you seen the sheer amount of exposed floor there is on this car?

does exposed floor = enough flow over top of diffuser?
What about beam wing design?

I do think the RB beam wing design could/will be added to the merc, as it in theory should be better at helping extraction through the diffuser

[Mchamilton]

It's coming from the suspension too. Undamped heave mode.

How is it 'coming from' the suspension? The suspension is moving as a consequence of the changing load under the car.
Its that severe change in the load that needs to be better controlled.

The suspension controls how quickly and how far the car rebounds upwards when the floor dies.

Of course, but they cant put infinitely stiff springs and dampers into the car can they. That would be another way to crudely patch the problem.
The fix realistically has to be to better manage the flows under the floor.
How, i have no idea

[mkay]

Looking at the Jeddah FP2 telemetry, it really does look like the Merc have much shorter gears than the Ferrari and RB. Wouldn’t this have an impact on ICE wear in the long run (hitting higher RPM)?

[dans79]

How is it 'coming from' the suspension? The suspension is moving as a consequence of the changing load under the car.
Its that severe change in the load that needs to be better controlled.

The suspension controls how quickly and how far the car rebounds upwards when the floor dies.

Of course, but they cant put infinitely stiff springs and dampers into the car can they. That would be another way to crudely patch the problem.
The fix realistically has to be to better manage the flows under the floor.
How, i have no idea

That's part of it, but they might also might be able to alter the suspension in a way that causes the front and rear to have different natural frequencies.

[matteosc]

The suspension controls how quickly and how far the car rebounds upwards when the floor dies.

Of course, but they cant put infinitely stiff springs and dampers into the car can they. That would be another way to crudely patch the problem.
The fix realistically has to be to better manage the flows under the floor.
How, i have no idea

That's part of it, but they might also might be able to alter the suspension in a way that causes the front and rear to have different natural frequencies.

The car has a natural frequency as a whole, which depends on overall mass, mass distribution and stiffness of front and rear. You do not have different "localized" natural frequencies.