Mercedes W13

[ringo]

Just report or vote the post down for technical inaccuracy. Don't respond to the troll.

Unless you provide technical proof, you are not in a position to decide what is "technical" "inaccurate" and downvote for it.
What makes your random opinion any more accurate than others?
Rather provide data and debate his opinion.
sneaky spitefulness is not how we learn. we need to share opinion and data.

Sidepods do not generate downforce, and if they do, it is insignificant. In most CFD analysis that you can find on sidepods, they are fairly neutral, or create a small amount of lift.

In relation to the system they might play a key role in total downforce creation (which was not stated).

In relation to porpoising, theoretically creating more downforce does not solve the problem, it actually contributes to it as it sucks the floor to the ground faster, potentially propagating the effect at a lower speed, making it more of an issue.

Finally - if the original comment had post the statement as a question, it would have been fine. If it was posed as an opinion it would have been fine. But it was posed as fact, and as such, is incorrect and inaccurate, so I voted it negatively.

I have provided a laymans explanation above at your request as you make a good point about learning.

What you may be inaccurate about is your perception about downforce.
The sidepods do contribute greatly to the creation of downforce.
How so?
By reducing lift. The F-1 car's total downforce is a sum of the forces acting on the lower and upper surfaces to put in simple terms.
If the upper surfaces, ie sidepods, cockpit, engine cover are not designed well they can have regions of lower pressure over them, contributing to lift and reducing overall downforce.

[Mchamilton]

Random thought, could a more powerful beam wing, say like on the rb18, help reduce the porpoising? By increasing overall extraction.

[ringo]

Maybe but consider the boundary layer.
When the boundary layer grows it contributes to and is the main reason for the flow choking under the car.
Extracting more air will result in the same boundary layer growth between the floor and the ground.

The boundary layer is determined by the reynold's number of the flow, air density, roughness of the underside of the floor, roughness of the track, air temperature and pressure, and mass flow under the car.
More extraction will drive the boundary growth. It is an unavoidable phenomenon.
Teams are bouncing less simply because they are riding higher to avoid the growing boundary layers from blocking the channel, or are bleeding the air perpendicular to the flow direction or some trick like that to limit the mass flow of air under the car.
I think they all know what to do to solve the problem. But the bouncing cars definitely are at higher downforce levels, because that floor gap is at the distance that causes choking. All of the them have same roughness of surfaces, same air properties under their cars. So a less bouncy car more than likely is making the downforce more efficiently or its being made at a higher proportion elsewhere. Or they simply found a way to bleed off the mass flow on the straights. Many things come to mind. Any of what I say here does not have to be the case.

[Marty_Y]

So I am no technical expert so I'm asking this as an exploratory question.

The problem with porpoising it that it happens at high speed?

The way to fix it is, if I'm understanding correctly, to have lower volume of air under the car or have air able to somehow leak out the sides? Or is this completely wrong?

Is this why teams have been looking at the edge of the floor? I.e. if you can get the edge of the floor to seal under a certain speed but not seal or do something to the the air at high-speed and also help with air around rear tyres to reduce drag then you may be able to solve porposiong?

If that is the case then it's most likely more difficult to solve where there is a higher overall circuit average speed?

Apologies, im trying to understand the issue Merc face but with very limited technical knowledge.

viewtopic.php?t=30265

Here's a link to a thread specifically about the issue you are interested in learning about, there's links to articles that explains the phenomenon and some great opinions from some very knowledgeable members.

[w1Y]

Thanks. I'll have a read through

[Vanja #66]

What you may be inaccurate about is your perception about downforce.
The sidepods do contribute greatly to the creation of downforce.
How so?
By reducing lift. The F-1 car's total downforce is a sum of the forces acting on the lower and upper surfaces to put in simple terms.
If the upper surfaces, ie sidepods, cockpit, engine cover are not designed well they can have regions of lower pressure over them, contributing to lift and reducing overall downforce.

This is an important job of the sidepods and their influence on overall downforce. However, equally important is shaping them so they help guide the air where it can contribute positively to overall downforce. And, we mustn't forget, they guide the air where it will contribute to aero balance as well. Sidepods are potentially (defined by rule boxes) the biggest projected surface which contributes to overall lift, tyres excluded for obvious reasons.

This makes them a uniqe asset, as they can be shaped to guide the air down (creating local lift) towards the floor, beam wing etc. Knowing that you can't do too much to reduce their lift (other than obscuring sidepods almost completely like W13), you can use it to your advantage. Very obvious examples this year are RB, AT and Alpine, it all depends on the teams approach. Seeing no flat coke-bottle sidepods of late 80s and 90s in recent years, gives an impression teams are very willing to let them generate lift in order to condition the flow to the rear exactly how they want it.

Maybe but consider the boundary layer.
When the boundary layer grows it contributes to and is the main reason for the flow choking under the car.
Extracting more air will result in the same boundary layer growth between the floor and the ground.

The boundary layer is determined by the reynold's number of the flow, air density, roughness of the underside of the floor, roughness of the track, air temperature and pressure, and mass flow under the car.
More extraction will drive the boundary growth. It is an unavoidable phenomenon.
Teams are bouncing less simply because they are riding higher to avoid the growing boundary layers from blocking the channel, or are bleeding the air perpendicular to the flow direction or some trick like that to limit the mass flow of air under the car.
I think they all know what to do to solve the problem. But the bouncing cars definitely are at higher downforce levels, because that floor gap is at the distance that causes choking. All of the them have same roughness of surfaces, same air properties under their cars. So a less bouncy car more than likely is making the downforce more efficiently or its being made at a higher proportion elsewhere. Or they simply found a way to bleed off the mass flow on the straights. Many things come to mind. Any of what I say here does not have to be the case.

Actually, in subsonic flow, the boundary layer thickness goes down with higher fluid velocity, all other things being equal. The flow chokes simply due to lower ride height when the car is sucked closer to the ground. FIA can solve the problem very easily if needed for next year, by increasing the tunnel height and mandating a minimal tunnel height relative to the plank or something like that. This would probably lead to somewhat lower performance, but if there are nasty accidents caused by floor choking mid-corner this year, there are simple solutions for these "ground-effect" floors.

[ringo]

All things wont be equal. laminar flow to turbulent and boundary layer tripping and all that jazz.
The top and bottom boundary layers can form a throat and that's where the choking starts.
Those two layer interactions are very important.

Also yes there is more involved like pressure ratio and heat capacities etc etc. Beyond the scope of the discussion and beyond my comfort zone of understanding.

But i think all teams are in the same boat.
The downstream pressure isn't as critical as the fluid properties if i remember correctly.

[Just_a_fan]

All things wont be equal. laminar flow to turbulent and boundary layer tripping and all that jazz.
The top and bottom boundary layers can form a throat and that's where the choking starts.
Those two layer interactions are very important.

What bottom boundary layer?

[ringo]

All things wont be equal. laminar flow to turbulent and boundary layer tripping and all that jazz.
The top and bottom boundary layers can form a throat and that's where the choking starts.
Those two layer interactions are very important.

What bottom boundary layer?

The road. You have the standing air over the ground. the floor of the car will exert a shear force on the air and shear it across the road. A shear force profile will develop between the floor and the road.
The road is very bumpy compared to the floor so i suspect turbulence.
It's an interesting thing to imagine, but its not the same as the text book boundary layer interacting with one surface.

compressible Couette flow

[Henri]

Unless you provide technical proof, you are not in a position to decide what is "technical" "inaccurate" and downvote for it.
What makes your random opinion any more accurate than others?
Rather provide data and debate his opinion.
sneaky spitefulness is not how we learn. we need to share opinion and data.

Sidepods do not generate downforce, and if they do, it is insignificant. In most CFD analysis that you can find on sidepods, they are fairly neutral, or create a small amount of lift.

In relation to the system they might play a key role in total downforce creation (which was not stated).

In relation to porpoising, theoretically creating more downforce does not solve the problem, it actually contributes to it as it sucks the floor to the ground faster, potentially propagating the effect at a lower speed, making it more of an issue.

Finally - if the original comment had post the statement as a question, it would have been fine. If it was posed as an opinion it would have been fine. But it was posed as fact, and as such, is incorrect and inaccurate, so I voted it negatively.

I have provided a laymans explanation above at your request as you make a good point about learning.

What you may be inaccurate about is your perception about downforce.
The sidepods do contribute greatly to the creation of downforce.
How so?
By reducing lift. The F-1 car's total downforce is a sum of the forces acting on the lower and upper surfaces to put in simple terms.
If the upper surfaces, ie sidepods, cockpit, engine cover are not designed well they can have regions of lower pressure over them, contributing to lift and reducing overall downforce.

Interesting

[zibby43]

[S E C T I O]

What you may be inaccurate about is your perception about downforce.
The sidepods do contribute greatly to the creation of downforce.
How so?
By reducing lift. The F-1 car's total downforce is a sum of the forces acting on the lower and upper surfaces to put in simple terms.
If the upper surfaces, ie sidepods, cockpit, engine cover are not designed well they can have regions of lower pressure over them, contributing to lift and reducing overall downforce.

This is an important job of the sidepods and their influence on overall downforce. However, equally important is shaping them so they help guide the air where it can contribute positively to overall downforce. And, we mustn't forget, they guide the air where it will contribute to aero balance as well. Sidepods are potentially (defined by rule boxes) the biggest projected surface which contributes to overall lift, tyres excluded for obvious reasons.

This makes them a uniqe asset, as they can be shaped to guide the air down (creating local lift) towards the floor, beam wing etc. Knowing that you can't do too much to reduce their lift (other than obscuring sidepods almost completely like W13), you can use it to your advantage. Very obvious examples this year are RB, AT and Alpine, it all depends on the teams approach. Seeing no flat coke-bottle sidepods of late 80s and 90s in recent years, gives an impression teams are very willing to let them generate lift in order to condition the flow to the rear exactly how they want it.

Maybe but consider the boundary layer.
When the boundary layer grows it contributes to and is the main reason for the flow choking under the car.
Extracting more air will result in the same boundary layer growth between the floor and the ground.

The boundary layer is determined by the reynold's number of the flow, air density, roughness of the underside of the floor, roughness of the track, air temperature and pressure, and mass flow under the car.
More extraction will drive the boundary growth. It is an unavoidable phenomenon.
Teams are bouncing less simply because they are riding higher to avoid the growing boundary layers from blocking the channel, or are bleeding the air perpendicular to the flow direction or some trick like that to limit the mass flow of air under the car.
I think they all know what to do to solve the problem. But the bouncing cars definitely are at higher downforce levels, because that floor gap is at the distance that causes choking. All of the them have same roughness of surfaces, same air properties under their cars. So a less bouncy car more than likely is making the downforce more efficiently or its being made at a higher proportion elsewhere. Or they simply found a way to bleed off the mass flow on the straights. Many things come to mind. Any of what I say here does not have to be the case.

Actually, in subsonic flow, the boundary layer thickness goes down with higher fluid velocity, all other things being equal. The flow chokes simply due to lower ride height when the car is sucked closer to the ground. FIA can solve the problem very easily if needed for next year, by increasing the tunnel height and mandating a minimal tunnel height relative to the plank or something like that. This would probably lead to somewhat lower performance, but if there are nasty accidents caused by floor choking mid-corner this year, there are simple solutions for these "ground-effect" floors.

Sorry if I ask you directly, but I see that beyond knowledge,you have kindness and patience, and sorry if it's a stupid question,i'm not a technic guy.Few years ago a type of swimsuit was unveiled,that reduced drag in the water so much that it was then banned. I thought it would be shortly before seeing similar concepts applied to the surfaces of an F1 to slow down / accelerate the flow in the various areas of the bodywork,where it is needed, but none of this has happened, is there a specific reason for this? Maybe the rules?Thanks if you would like to reply and still sorry for your time.

[Vanja #66]

The road. You have the standing air over the ground. the floor of the car will exert a shear force on the air and shear it across the road. A shear force profile will develop between the floor and the road.
The road is very bumpy compared to the floor so i suspect turbulence.
It's an interesting thing to imagine, but its not the same as the text book boundary layer interacting with one surface.

compressible Couette flow

In the example of Couette flow you've given, there is no fluid movement on the stationary plate (i.e. road surface) so there is no boundary layer formation. This is well known.



Couette flow is not entirely comparable to floor going over the road, as Couette flow is stationary flow. And car racing is anything but stationary...

Sorry if I ask you directly, but I see that beyond knowledge,you have kindness and patience, and sorry if it's a stupid question,i'm not a technic guy.Few years ago a type of swimsuit was unveiled,that reduced drag in the water so much that it was then banned. I thought it would be shortly before seeing similar concepts applied to the surfaces of an F1 to slow down / accelerate the flow in the various areas of the bodywork,where it is needed, but none of this has happened, is there a specific reason for this? Maybe the rules?Thanks if you would like to reply and still sorry for your time.

Never apologize for asking questions. It's the rules, yes, such surface treatment of F1 bodywork would consistute uneven surfaces which would go against the minimal bodywork radii rules. If a team would try to explain this as surface manufacturing imperfections, the pattern would clearly be visible and FIA woudn't accept this explanation. It's very likely one or more teams have tried doing this years ago, but the FIA stopped them right away.

[Stu]

The road. You have the standing air over the ground. the floor of the car will exert a shear force on the air and shear it across the road. A shear force profile will develop between the floor and the road.
The road is very bumpy compared to the floor so i suspect turbulence.
It's an interesting thing to imagine, but its not the same as the text book boundary layer interacting with one surface.

compressible Couette flow

In the example of Couette flow you've given, there is no fluid movement on the stationary plate (i.e. road surface) so there is no boundary layer formation. This is well known.

https://i.ibb.co/p6qXG1n/640px-Laminar-shear-svg.png

Couette flow is not entirely comparable to floor going over the road, as Couette flow is stationary flow. And car racing is anything but stationary...

Sorry if I ask you directly, but I see that beyond knowledge,you have kindness and patience, and sorry if it's a stupid question,i'm not a technic guy.Few years ago a type of swimsuit was unveiled,that reduced drag in the water so much that it was then banned. I thought it would be shortly before seeing similar concepts applied to the surfaces of an F1 to slow down / accelerate the flow in the various areas of the bodywork,where it is needed, but none of this has happened, is there a specific reason for this? Maybe the rules?Thanks if you would like to reply and still sorry for your time.

Never apologize for asking questions. It's the rules, yes, such surface treatment of F1 bodywork would consistute uneven surfaces which would go against the minimal bodywork radii rules. If a team would try to explain this as surface manufacturing imperfections, the pattern would clearly be visible and FIA woudn't accept this explanation. It's very likely one or more teams have tried doing this years ago, but the FIA stopped them right away.

Looking at it from a practical perspective any airflow on the track surface caused by the cars is more likely to move ahead of the car (like a bow wave on a boat); however, that would be a single car on a still day with zero temperature difference between ambient air and track surface. In essence the car would push any static air (or boundary layer phenomenon) out of the way - before it interacted with the under car flow.

In reality…
There will never be static air on the track surface, there will always be some measurable breeze, a temperature difference between air and track surface or other cars on track.

On porpoising….
Normally the car will be pushed onto the track through the centre of pressure, if that is located forward of the CoG the front of the car will tend to fully compress first, followed by the rear. If the ‘choke’ is caused by the rear of the car being pushed to the ground, the cycle begins!! If the ‘choke’ is caused by the front of the car being pushed to the ground, it will create a cycle that only really exhibits on the front axle (so the car will look as though it is bouncing).
If the CoP is behind the CoG the car will be pushed to the ground in the opposite order, if the ‘choke’ is caused by the rear of the car being pushed into the ground, the rear axle will experience this same bouncing motion; if the ‘choke’ is caused by the front of the car being pushed into the ground, it will only then start to porpoise. However this will be in the opposite direction to the previous example.

To a degree if you only have the single axle bounce it can be controlled by ride height, bump rubbers, etc. if you have the full monty, no amount of passive suspension will control it (while allowing the car to be drivable at racing speeds), it is a purely aerodynamic issue (essentially the car CoP or CoG needs to be moved).

It is entirely possible that Mercedes deliberately ran a set-up that allowed the porpoising (also - fuel levels impact CoG…), which would be the ultimate sandbagging

It is also highly likely that ‘some’ rake could totally cure the problem (a la RedBull day 3).

[tok-tokkie]

I have only seen a few of the video clips linked on F1 Technical.
What has struck me is how close the Merc floor is to the road. It is just skimming the track in the vids I have seen.
The Red Bull, Ferrari (& McLaren?) are much further away.
There have been CFD shots showing the vortex running down the side of the floor forming a "skirt" to the floor &, hence, the tunnel.
In particular Red Bull has a wedge shaped vane creating a really strong vortex to provide this seal.
I suspect that Mercedes will adopt the same tactic to seal the floor. Then they need not run so close to the road. Then the choking problem will be resolved and the porpoising eliminated.
I actually wonder if they anticipated this all along (or certainly after Barcelona) and have the revised floor ready for the race.