I used to get it on my Kawi around 48mph, but only if I didn't damp it with a very light touch on the bars. It would stop above 50. Generally things on the rear of the bike, or anything that reduces weight on the front exacerbates it.Postmoe wrote: ↑Wed Mar 09, 2022 5:53 pmI don't know if it's related but motorcycle wobble can be driver induced but is determined by the motorbike's characteristics AND aero. Specially if the wavelength surpasses normal human reaction times.Just_a_fan wrote: ↑Wed Mar 09, 2022 5:21 pmThe increasing and decreasing angle of attack of the aircraft on approach and as they approach touchdown is classic POI. The issue started well before the wheels first touched the ground. Then the pilot tried to correct the situation with control inputs.vorticism wrote: ↑Wed Mar 09, 2022 5:03 pm
Wrong again. See my other prev posts. The agency of the pilot/driver is irrelevant. The physical phenomenon is governed by the same forces. What's known as a type of bounced landing. PIO is a general term and could happen at various altitude, be applied to numerous types of faults.
https://en.wikipedia.org/wiki/Bounced_landing
Even the Shuttle pilots had an issue with PIO during the early test flights. The control logic was altered to add some damping of the pilots' control inputs to help prevent PIO in future by slowing the response of the controls to inputs.
You can see the PIO starting before the wheels touch the runway. Once they do, the pilot then over controls and the vehicle under goes further oscillations in the air.
Anyway, aircraft PIOs or undercarriage bounces are off topic for the aero-created porpoising of the current F1 cars.
BTW, I experienced it in a very drastic way at "not so high" speeds, and suspected the unusual positioning of the bmwF800R fuel tank (rear). It stopped when I changed my backpack: I think it acted as a moving shark fin.
I brought this up during the first test, but extremely unlikely for a few reasonscooken wrote: ↑Sat Mar 19, 2022 12:33 pmTo our CFD subject matter experts: do the models these days include any kinematics and elasticity, or is everything still limited to rigid bodies and fixed ride height? In other words, is there any accounting for real time suspension movement within the sim. If so is that statics only or are viscous and inertial effects included?
I am assuming they set a fixed rigid suspension position based on estimated or iterated lift and centre of pressure. In this limited framework predicting/simulating porpoising is clearly very difficult, its a violation of some fundamental assumptions.
Yea pretty much as I thought. So testing and track measurements are really crucial for solving this.Hoffman900 wrote: ↑Sat Mar 19, 2022 1:14 pmI brought this up during the first test, but extremely unlikely for a few reasonscooken wrote: ↑Sat Mar 19, 2022 12:33 pmTo our CFD subject matter experts: do the models these days include any kinematics and elasticity, or is everything still limited to rigid bodies and fixed ride height? In other words, is there any accounting for real time suspension movement within the sim. If so is that statics only or are viscous and inertial effects included?
I am assuming they set a fixed rigid suspension position based on estimated or iterated lift and centre of pressure. In this limited framework predicting/simulating porpoising is clearly very difficult, its a violation of some fundamental assumptions.
1) CFD really struggles with turbulent air / vortex shedding. It’s a very very hard thing to model accurately. Even NASA, Boeing, Airbus, Lockheed Martin, etc all struggle with this.
2) You would need a suspension / chassis model.This would be extremely complex and being a model, it would have a lot of errors as well. Basically everything is a spring and they are hell to model. To quote a PhD friend “infinite stiffness only exists in undergraduate text books”.
3) no F1 team has the computing power to do both. The simulators probably reduce the resolution of all of it a lot. This is clear because Merc obviously can’t get a hold of it despite their resources and I’m sure tireless efforts at the factory.
Wind tunnel models are scaled and again no suspension. Even if they did, a scale chassis won’t go in resonance like a full scale.
They are and I think F1’s over reliance on simulations makes for a worst product.cooken wrote: ↑Sat Mar 19, 2022 1:37 pmYea pretty much as I thought. So testing and track measurements are really crucial for solving this.Hoffman900 wrote: ↑Sat Mar 19, 2022 1:14 pmI brought this up during the first test, but extremely unlikely for a few reasonscooken wrote: ↑Sat Mar 19, 2022 12:33 pmTo our CFD subject matter experts: do the models these days include any kinematics and elasticity, or is everything still limited to rigid bodies and fixed ride height? In other words, is there any accounting for real time suspension movement within the sim. If so is that statics only or are viscous and inertial effects included?
I am assuming they set a fixed rigid suspension position based on estimated or iterated lift and centre of pressure. In this limited framework predicting/simulating porpoising is clearly very difficult, its a violation of some fundamental assumptions.
1) CFD really struggles with turbulent air / vortex shedding. It’s a very very hard thing to model accurately. Even NASA, Boeing, Airbus, Lockheed Martin, etc all struggle with this.
2) You would need a suspension / chassis model.This would be extremely complex and being a model, it would have a lot of errors as well. Basically everything is a spring and they are hell to model. To quote a PhD friend “infinite stiffness only exists in undergraduate text books”.
3) no F1 team has the computing power to do both. The simulators probably reduce the resolution of all of it a lot. This is clear because Merc obviously can’t get a hold of it despite their resources and I’m sure tireless efforts at the factory.
Wind tunnel models are scaled and again no suspension. Even if they did, a scale chassis won’t go in resonance like a full scale.
By the way it doesn't take a PhD to realize that many of the assumptions we lean on in undergraduate education go out the window very quickly in real world application. The most egregious one I come across all the time is assuming small displacement and rotation / linear behaviour. Simplifying assumptions are great and often necessary to suit scope and budget etc but they are very easily abused.
Eh, as an FE analyst I kinda disagree. FSI and multiphysics are continuously gaining traction, and I would rather see F1 innovating in this area too rather than being artificially handicapped.Hoffman900 wrote: ↑Sat Mar 19, 2022 1:42 pmThey are and I think F1’s over reliance on simulations makes for a worst product.cooken wrote: ↑Sat Mar 19, 2022 1:37 pmYea pretty much as I thought. So testing and track measurements are really crucial for solving this.Hoffman900 wrote: ↑Sat Mar 19, 2022 1:14 pm
I brought this up during the first test, but extremely unlikely for a few reasons
1) CFD really struggles with turbulent air / vortex shedding. It’s a very very hard thing to model accurately. Even NASA, Boeing, Airbus, Lockheed Martin, etc all struggle with this.
2) You would need a suspension / chassis model.This would be extremely complex and being a model, it would have a lot of errors as well. Basically everything is a spring and they are hell to model. To quote a PhD friend “infinite stiffness only exists in undergraduate text books”.
3) no F1 team has the computing power to do both. The simulators probably reduce the resolution of all of it a lot. This is clear because Merc obviously can’t get a hold of it despite their resources and I’m sure tireless efforts at the factory.
Wind tunnel models are scaled and again no suspension. Even if they did, a scale chassis won’t go in resonance like a full scale.
By the way it doesn't take a PhD to realize that many of the assumptions we lean on in undergraduate education go out the window very quickly in real world application. The most egregious one I come across all the time is assuming small displacement and rotation / linear behaviour. Simplifying assumptions are great and often necessary to suit scope and budget etc but they are very easily abused.
With these big rule changes they should have allowed more cap space for on track testing. Teams having to develop their cars heavily over the first 1/4 - 1/3 of the season isn’t conducive to a good show and nullifies any work to make the cars follow closer.
They are, but you would need to;cooken wrote: ↑Sat Mar 19, 2022 1:48 pmEh, as an FE analyst I kinda disagree. FSI and multiphysics are continuously gaining traction, and I would rather see F1 innovating in this area too rather than being artificially handicapped.Hoffman900 wrote: ↑Sat Mar 19, 2022 1:42 pmThey are and I think F1’s over reliance on simulations makes for a worst product.cooken wrote: ↑Sat Mar 19, 2022 1:37 pm
Yea pretty much as I thought. So testing and track measurements are really crucial for solving this.
By the way it doesn't take a PhD to realize that many of the assumptions we lean on in undergraduate education go out the window very quickly in real world application. The most egregious one I come across all the time is assuming small displacement and rotation / linear behaviour. Simplifying assumptions are great and often necessary to suit scope and budget etc but they are very easily abused.
With these big rule changes they should have allowed more cap space for on track testing. Teams having to develop their cars heavily over the first 1/4 - 1/3 of the season isn’t conducive to a good show and nullifies any work to make the cars follow closer.
I do also think the testing restrictions are way overkill. End of the day it's still a race car and needs track time.
I reckon the tires are the biggest challenge there. I don't think deformable bodywork would be all that necessary, maybe the floor ahead of the rear tyres for these cars but some are adding stays to keep that part rigid so maybe not. Perhaps the FW elements...for dynamics substructuring could be put to good use here.Hoffman900 wrote: ↑Sat Mar 19, 2022 1:52 pmThey are, but you would need to;cooken wrote: ↑Sat Mar 19, 2022 1:48 pmEh, as an FE analyst I kinda disagree. FSI and multiphysics are continuously gaining traction, and I would rather see F1 innovating in this area too rather than being artificially handicapped.Hoffman900 wrote: ↑Sat Mar 19, 2022 1:42 pm
They are and I think F1’s over reliance on simulations makes for a worst product.
With these big rule changes they should have allowed more cap space for on track testing. Teams having to develop their cars heavily over the first 1/4 - 1/3 of the season isn’t conducive to a good show and nullifies any work to make the cars follow closer.
I do also think the testing restrictions are way overkill. End of the day it's still a race car and needs track time.
1) model the tub accurately and its stiffness / resonance, which will change when things are bolted onto it
2) model all the joints of all suspension accurately in terms of flex,
3) model body work resonance (think flutter) accuruatetly
4) model the shocks
5) model the springs , flex , resonance in the rest of the suspension
6) model the tire
The run this model in concurrence with CFD. You would need to rent time at Los Alamos to even have a sniff at this. And with CFD missing or incorrectly getting turbulence wrong and how hard vortex shedding induced resonance is to model (think skyscrapers and turbulence induced acoustics) and the model would be wrong anyway.
first time i knew about this , wow so limited time and limited speed , why invest in a tunnel evenHoffman900 wrote: ↑Sat Mar 19, 2022 2:37 pmThe 180km/h limit blows my mind still. I was shocked to be reminded of that (must have forgotten).
I really do think with the wholesale changes, they should have allowed more on track testing this year.