Aero analysis for F1 2022 based on CFD result

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jjn9128
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Re: Aero analysis for F1 2022 based on CFD result

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Fluido wrote:
Sat Apr 16, 2022 5:37 pm
Latios wrote:
Sat Mar 26, 2022 7:41 pm
The difference between whether the fences are out-wash or not, it's clear that outwash fences can significantly improve the downforce under the floor.
https://pic1.zhimg.com/80/v2-28e569f2 ... _720w.jpg

Does diffuser stall in left case where fences dont push air out?
(What is diffuser AoA in part with largest slope(I think this would be diffuser exit)?

In general does vortex flow in tunnels delay flow separation, so we can push diffuser AoA to the limit?
It's a 2 way propogation - the strakes make low pressure (-ve Cp) which lowers the pressure at the floor throat - which lowers the pressure at the diffuser kick - which propagates up the throat. That diffuser isn't stalled, it's just not making DF.
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"There is one big friend. It is downforce. And once you have this it’s a big mate and it’s helping a lot." Robert Kubica

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Re: Aero analysis for F1 2022 based on CFD result

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jjn9128 wrote:
Sat Apr 16, 2022 7:19 pm
Fluido wrote:
Sat Apr 16, 2022 5:37 pm
Latios wrote:
Sat Mar 26, 2022 7:41 pm
The difference between whether the fences are out-wash or not, it's clear that outwash fences can significantly improve the downforce under the floor.
https://pic1.zhimg.com/80/v2-28e569f2 ... _720w.jpg

Does diffuser stall in left case where fences dont push air out?
(What is diffuser AoA in part with largest slope(I think this would be diffuser exit)?

In general does vortex flow in tunnels delay flow separation, so we can push diffuser AoA to the limit?
It's a 2 way propogation - the strakes make low pressure (-ve Cp) which lowers the pressure at the floor throat - which lowers the pressure at the diffuser kick - which propagates up the throat. That diffuser isn't stalled, it's just not making DF.
I ask in general, does vortex flow delay flow separation compare to normal "clean" flow?

How do you explain very different pressure distribution of underfloor Latios vs Vyssion?

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jjn9128
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Re: Aero analysis for F1 2022 based on CFD result

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Fluido wrote:
Sat Apr 16, 2022 7:25 pm
jjn9128 wrote:
Sat Apr 16, 2022 7:19 pm
Fluido wrote:
Sat Apr 16, 2022 5:37 pm


Does diffuser stall in left case where fences dont push air out?
(What is diffuser AoA in part with largest slope(I think this would be diffuser exit)?

In general does vortex flow in tunnels delay flow separation, so we can push diffuser AoA to the limit?
It's a 2 way propogation - the strakes make low pressure (-ve Cp) which lowers the pressure at the floor throat - which lowers the pressure at the diffuser kick - which propagates up the throat. That diffuser isn't stalled, it's just not making DF.
I ask in general, does vortex flow delay flow separation compare to normal "clean" flow?

How do you explain very different pressure distribution of underfloor Latios vs Vyssion?
There will be a benefit from the low pressure core of the vortex reducing the adverse pressure gradient.

Our car was run with a massive RR RH (because the FOM model had a lot of rake) so our diffuser is about 120mm in the air :lol: :lol:
#aerogandalf
"There is one big friend. It is downforce. And once you have this it’s a big mate and it’s helping a lot." Robert Kubica

Fluido
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Re: Aero analysis for F1 2022 based on CFD result

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jjn9128 wrote:
Sat Apr 16, 2022 7:36 pm
Fluido wrote:
Sat Apr 16, 2022 7:25 pm
jjn9128 wrote:
Sat Apr 16, 2022 7:19 pm


It's a 2 way propogation - the strakes make low pressure (-ve Cp) which lowers the pressure at the floor throat - which lowers the pressure at the diffuser kick - which propagates up the throat. That diffuser isn't stalled, it's just not making DF.
I ask in general, does vortex flow delay flow separation compare to normal "clean" flow?

How do you explain very different pressure distribution of underfloor Latios vs Vyssion?
There will be a benefit from the low pressure core of the vortex reducing the adverse pressure gradient.

Our car was run with a massive RR RH (because the FOM model had a lot of rake) so our diffuser is about 120mm in the air :lol: :lol:
What is height of inlet undertray,throat and diffuser exit, in real F1 today? 35cm-5cm-50cm ?

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godlameroso
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Re: Aero analysis for F1 2022 based on CFD result

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jjn9128 wrote:
Sat Apr 16, 2022 7:36 pm
Fluido wrote:
Sat Apr 16, 2022 7:25 pm
jjn9128 wrote:
Sat Apr 16, 2022 7:19 pm


It's a 2 way propogation - the strakes make low pressure (-ve Cp) which lowers the pressure at the floor throat - which lowers the pressure at the diffuser kick - which propagates up the throat. That diffuser isn't stalled, it's just not making DF.
I ask in general, does vortex flow delay flow separation compare to normal "clean" flow?

How do you explain very different pressure distribution of underfloor Latios vs Vyssion?
There will be a benefit from the low pressure core of the vortex reducing the adverse pressure gradient.

Our car was run with a massive RR RH (because the FOM model had a lot of rake) so our diffuser is about 120mm in the air :lol: :lol:
Ahem

Image

This says vortices are themselves adverse pressure gradients. The wing tip vortices have a force vector opposite to the direction of travel. They are a source of drag.

How would the vortices generated in the tunnel reduce adverse pressure gradients when the vortices themselves are adverse pressure gradients. Is the pressure from the vortex wall in effect compressing the boundary layer against the tunnels?

What about the co-rotating vortices that flank the plank? Isn't that being driven by the tunnel vortices helping to seal the plank area? That would mean the floor is some type of surfboard NACA duct.

Image

If the floor is doing something like this, then the strakes make sense as they'd strengthen the inwashing vortices on either side of the plank.
Saishū kōnā

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godlameroso
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Re: Aero analysis for F1 2022 based on CFD result

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I understand better than you it seems my cowardly downvoting friend. Adverse as in reversing from the direction of flow. Downvoting people because YOU don't understand is the lamest thing I've ever seen. It makes this place seem like facebook, I've seen more legit advice on tik tok.

adverse
ad-ˈvərs
ADJECTIVE
acting against or in a contrary direction : hostile
hindered by adverse winds
Saishū kōnā

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jjn9128
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Re: Aero analysis for F1 2022 based on CFD result

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Fluido wrote:
Sat Apr 16, 2022 9:07 pm
jjn9128 wrote:
Sat Apr 16, 2022 7:36 pm
Fluido wrote:
Sat Apr 16, 2022 7:25 pm

I ask in general, does vortex flow delay flow separation compare to normal "clean" flow?

How do you explain very different pressure distribution of underfloor Latios vs Vyssion?
There will be a benefit from the low pressure core of the vortex reducing the adverse pressure gradient.

Our car was run with a massive RR RH (because the FOM model had a lot of rake) so our diffuser is about 120mm in the air :lol: :lol:
What is height of inlet undertray,throat and diffuser exit, in real F1 today? 35cm-5cm-50cm ?
I advise checking out the rules :wink: 25-30 > 5 > 30 would be ballpark though
#aerogandalf
"There is one big friend. It is downforce. And once you have this it’s a big mate and it’s helping a lot." Robert Kubica

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vorticism
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Re: Aero analysis for F1 2022 based on CFD result

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godlameroso wrote:
Tue Apr 19, 2022 3:39 pm
This says vortices are themselves adverse pressure gradients. The wing tip vortices have a force vector opposite to the direction of travel. They are a source of drag.
Conceptually you could have an adverse pressure gradient arising from two adjacent gas/fluid flows moving in opposition to each other, but it would be hard to compare it to boundary layer formation on a solid surface, as the two fluids in sheer would tend to entrain one another leading to more complex interactions other than boundary layer thickening.

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Vyssion
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Re: Aero analysis for F1 2022 based on CFD result

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godlameroso wrote:
Tue Apr 19, 2022 3:39 pm
jjn9128 wrote:
Sat Apr 16, 2022 7:36 pm
Fluido wrote:
Sat Apr 16, 2022 7:25 pm

I ask in general, does vortex flow delay flow separation compare to normal "clean" flow?

How do you explain very different pressure distribution of underfloor Latios vs Vyssion?
There will be a benefit from the low pressure core of the vortex reducing the adverse pressure gradient.

Our car was run with a massive RR RH (because the FOM model had a lot of rake) so our diffuser is about 120mm in the air :lol: :lol:
Ahem

https://anopic.us/MrFgyd9KaBdeNg7CeBpyN ... lTSAej.png

This says vortices are themselves adverse pressure gradients. The wing tip vortices have a force vector opposite to the direction of travel. They are a source of drag.

How would the vortices generated in the tunnel reduce adverse pressure gradients when the vortices themselves are adverse pressure gradients. Is the pressure from the vortex wall in effect compressing the boundary layer against the tunnels?

What about the co-rotating vortices that flank the plank? Isn't that being driven by the tunnel vortices helping to seal the plank area? That would mean the floor is some type of surfboard NACA duct.

https://www.researchgate.net/profile/Ka ... eading.jpg

If the floor is doing something like this, then the strakes make sense as they'd strengthen the inwashing vortices on either side of the plank.
Because all an "adverse pressure gradient" is, is when the static pressure increases in the direction of a flow.

That's it... nothing more.

Increasing pressure is roughly the same idea as increasing it's potential energy, which leads to a reduction in kinetic energy (from the dynamic pressure portion of the total pressure equation) and therefore an overall average decceleration of the flow.

I mentioned it on the last page, but here's a quote from that post:
https://www.f1technical.net/forum/view ... #p1054893
This is something which keeps cropping up around the forum lately, where there is this idea that "faster moving air has less pressure" or something...

L. J. Clancy put it most succinctly imo:
"To distinguish it from the total and dynamic pressures, the actual pressure of the fluid, which is associated not with its motion but with its state, is often referred to as the static pressure, but where the term pressure alone is used it refers to this static pressure."

Total Pressure = Static Pressure + Dynamic Pressure
Or another (albeit simplistic) way to look at it...
Total Energy of Fluid = Temperature Energy of Fluid + Movement Energy of Fluid

Bernoulli's equation only holds for air travelling along a single streamline; something often overlooked. What that means is that along that streamline, energy flows between static (static pressure) and dynamic (dynamic pressure) states, but their sum is always constant (total pressure). The dynamic pressure term is just something that represents the decrease in the static pressure due to the change in velocity of the fluid. If you were to stagnate that dynamic pressure, then it would revert back to being just plain old static pressure to ensure the constant total pressure summation.

Fast moving air isn't just "low pressure" on it's own -- there's more going on -- it just has a portion of it's static pressure "converted" to dynamic pressure. The faster the air, the larger that amount of conversion is. Less bouncing on walls doesn't mean less pressure. Slower moving molecules denotes less average kinetic energy of the particles, which in turn, denotes a lower temperature of the air.
Since the air right down on the surface, well within the boundary layer, is travelling slower, it is more affected by the adverse pressure gradient serving to deccelerate the flow. And if you continue to deccelerate, meaning over time you're slowing down the average airspeed in that region, you will eventually slow down enough that your velocity hits zero (and then negative). At that point, you're flow is "stalled" or "separated".

Turbulent boundary layers can withstand greater adverse pressure gradients because they have "mixing" within them; rather than laminar layers... so there is energy transport within the boundary "layers". Meaning that the air on the surface, just like with a laminar boundary layer, gets mixed up this time with a bit of higher energy air.

As such, it takes a larger upwind increase in static pressure in order to overcome that mixing effect, slow down the airflow velocity, and then stall the boundary layer. This is why vortex generators are a thing at all; it's because they promote that mixing in the boundary layer by forcing vortical flow regimes at a small enough scale so that they increase the boundary layers ability to withstand the increasing static pressure in the direction it travels (the adverse pressure gradient), which keeps the boundary layer attached for longer: a beneficial effect.

To your second point, the image you used to show co-rotating vortices is a delta wing -- not a plank. It's a very specific form of lift generation dominated by flow separation and vortex shape control (with secondary and tertiary vortices too), whilst trying to not cause the vortices to burst.

To your question about the plank itself though, any pressure differential on any object travelling forward through a fluid will create a vortical structure of some kind. Given the shape of the plank + base of the monocoque and sidepod sculpting, plus the fact that you don't want a lot going on in that area to begin with (you are trying to promote clean air flowing into your floor region and pushing all the messy stuff outwards) there probably is some kind of region of velocity curl going on, but I'd say it's somewhat minimal.

Take a look at these few still images from the CFD I did with jjn on the Perrinn 2017 F1 Car

Image
Image
Image

You can see the "red" total pressure coefficient lines there... the way the scale / legend works for these images is that anything black means "undisturbed from freestream". Red denotes "a little bit of influence and energy loss in the flow" and blue means a LOT of energy loss and influence going on. Right where the floor begins, there's just not that much going on because the front corners are already working to push the Y250 vortex out, to promote clean airflow into the floor.

For anyone who wants to look at some more images up/down-stream of these ones here, here's a direct link to the post I pulled them from.
viewtopic.php?p=816248#p816248
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Stu
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Re: Aero analysis for F1 2022 based on CFD result

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Thanks for that, Vyssion.

Do you think that the teams running the big undercuts are attempting to do so in order to re-energise the airflow by creating an adverse pressure gradient in that area to improve flow structures around the side-pods and floor edge?
Could this be why the Mercedes is being called ‘high drag’ - because the airflow has become de-energised in the zone where it is most important (leading to a poorer performing rear wing, beam wing (and consequently affecting the underfloor performance)? If it suddenly gets into a zone where everything ‘works’ it overpowers the platform control, that could induce the porpoising.
Perspective - Understanding that sometimes the truths we cling to depend greatly on our own point of view.

michael202223
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Re: Aero analysis for F1 2022 based on CFD result

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The description of F1 2022 based on CFD result in this post was very helpful to me, very profitable, thanks a lot :D

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variante
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Re: Aero analysis for F1 2022 based on CFD result

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Vyssion wrote:
Fri Apr 15, 2022 11:31 pm
To the people reading this, let me know below if you'd like to see a write up on "what lift really is" or something...
I'd like that. Mostly because i happened to bump into papers titled something like "new theory of lift" and they either look still incomplete or proper BS. Essentially, nobody seems to actually know. And, since i have my own BS swirling in my head, i'd be great to have more knowledgeable people telling if and where i'm wrong.
But the topic would probably deserve its own thread.

Hopefully, more people are interested in discussing the true nature behind aerodynamic forces...

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SiLo
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Re: Aero analysis for F1 2022 based on CFD result

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variante wrote:
Wed Apr 20, 2022 12:29 pm
Vyssion wrote:
Fri Apr 15, 2022 11:31 pm
To the people reading this, let me know below if you'd like to see a write up on "what lift really is" or something...
I'd like that. Mostly because i happened to bump into papers titled something like "new theory of lift" and they either look still incomplete or proper BS. Essentially, nobody seems to actually know. And, since i have my own BS swirling in my head, i'd be great to have more knowledgeable people telling if and where i'm wrong.
But the topic would probably deserve its own thread.

Hopefully, more people are interested in discussing the true nature behind aerodynamic forces...
Second this, I love learning about aero stuff.
Felipe Baby!

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Stu
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Re: Aero analysis for F1 2022 based on CFD result

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variante wrote:
Wed Apr 20, 2022 12:29 pm
Vyssion wrote:
Fri Apr 15, 2022 11:31 pm
To the people reading this, let me know below if you'd like to see a write up on "what lift really is" or something...
I'd like that. Mostly because i happened to bump into papers titled something like "new theory of lift" and they either look still incomplete or proper BS. Essentially, nobody seems to actually know. And, since i have my own BS swirling in my head, i'd be great to have more knowledgeable people telling if and where i'm wrong.
But the topic would probably deserve its own thread.

Hopefully, more people are interested in discussing the true nature behind aerodynamic forces...
Another +1 for this.
I think that I ‘know’ what it is, but I would guess that a basic understanding is not an adequate description!
Perspective - Understanding that sometimes the truths we cling to depend greatly on our own point of view.

SmallSoldier
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Re: Aero analysis for F1 2022 based on CFD result

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variante wrote:
Wed Apr 20, 2022 12:29 pm
Vyssion wrote:
Fri Apr 15, 2022 11:31 pm
To the people reading this, let me know below if you'd like to see a write up on "what lift really is" or something...
I'd like that. Mostly because i happened to bump into papers titled something like "new theory of lift" and they either look still incomplete or proper BS. Essentially, nobody seems to actually know. And, since i have my own BS swirling in my head, i'd be great to have more knowledgeable people telling if and where i'm wrong.
But the topic would probably deserve its own thread.

Hopefully, more people are interested in discussing the true nature behind aerodynamic forces...
Sign me up too please! I’m sure it would be a great read