Why do Diffusers have Strakes/Fins?
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- Опубликовано: 1 апр 2015
- Enough comedy, lets get serious. I see diffuser strakes explained incorrectly all over the place, and thought I would clear it up.
Table of contents:
1:00 - Strakes don't straighten the flow
2:00 - Strakes aren't vortex generators
3:00 - Tyre Squirt and the real reason behind strakes
6:00 - Managing floor vortices 
Авто/Мото
that sketch clearly displays the most efficient Diffuser-to-rear-wheel-size Ratio
Drawn to scale,of course.
My team is designing a diffuser. This is a great help. Thank you.
Thank you for your videos, I'm in aviation and I find motorsports aerodynamics fascinating especially Formula 1. Your channel was created for me haha!
You haven't mentioned separation of the air flow so when the diffuser stalls, it doesn't entirely stall. This enables to have the diffuser with different angles of attack, so it can work effectively on different speeds.
Spend hours planning his lesson. Didn't take 2 seconds to think how a fine tipped marker will show up on video. 😅 Great lesson though. Keep them coming.
a beautiful example of the L- or S shapes of the strakes , is the F2004! thx for mind blowing !
Brilliant, you explain in such a way that it becomes easier to understand. A great help with my studies.
Could you make a video on the blown diffuser please?
So happy I found your channel! Makes me more excited I decided to major in engineering!
“Talked to and ex f1 person”. Little did we know he had cracked time travel and actually just talked to his future self
Super helpful. I'm currently designing a diffuser for my car and this has given me some info to help make a couple changes that should improve it
Hello, I'll be doing the same soon also, what material do you plan on using?
@@countblah7099 I actually 3d printed it for a one time use shell, then covered it in fiberglass
I love your drawings! keep up the good work
Kyle - near the end of this video you mention the use of L shaped strakes in older diffuser designs to move the vortices closer to the ground.I understand how this would work, but my question is why is this an old design that is no longer used if it is better?
huntos83 he was saying in another video, modern f1 cars are built to meet class racing specifications, so I cannot pull up and race in the batmobile. It must built according to the rules.
dangerous probably
@@Planktarded do the new rules specify that diffuser strakes cannot be L-shaped?
It has sharp edges so prolly something to do with car laws not allowing them bc they are too dangerous
Is there any specific examples of cars with these? I’ve been looking and can’t seem to find any
Channel is called Kyle drives, yet I've seen him drive once lol
I love your videos so much ♥️
Great explanation!
Fantastic video!
excellent video!
Good stuff!
Fantastic!
Awesome explanation! How does one block tyre squirt at the front wheels though?
Could you do a vid on what would be the general aero shapes a drag racing car should look for, from the mild to the wild depending of the vehicle's speed of course.
Will it affect my car in any way if i remove the front strakes? Some people say they help deflect air into the radiator, others say they help improve the aerodynamics of the car hence better fuel.
Question for near the end of the video. You talk about vorticies created by the strakes helping to "block" the tire squirt from coming over. Also, in your diffuser video you talk about how the actual turning direction of the vortex has a lot to do with "blocking" side flow (this is specific to the part of the video where you discuss how canard's vortex actually rotates the wrong way to actually provide the sealing affect).
With the rotation of the vorticies on the strake in the diffuser, aren't they rotating in the wrong direction for them to be blocking the tire squirt (or any incoming side flow)? Or does the vortex absorb the tire squirt and lessen it's affect that way?
Well, for the canards case because the vortex is high, it's the rotation direction at the floor that we are concerned with. I.e. you want the vortex pushing the air out from the floor, not pulling it in. For the strake vortices, they are actually spanning the gap between the ground and the strake, so the vortex itself is entraining the flow into its centre. That way the core is acting almost like a physical wall, and the direction of the vortex is largely irrelevant. It would actually be preferable to have them spinning the other way, but there is no way I can think of doing this that doesn't adversely affect diffuser performance. Make sense?
Yep, that makes perfect sense. Thanks for the clarification!
THANK YOU MAN.
Thank you. So now the question is where to position them at best
So with the high pressure area in front of the tire that comes from being squished by the wheel, mostly applying to slick tires, would it make sense to reduce that with a kind of arrow that would deflect the air left and right minimizing the full stream of air from hitting the tire head on? more referring to full body cars not open wheel < O===~~~
So frkn cool. You rock. ✊
Also
On those l kicks
Is it correct to presume that those vortices are on the leading edge as well?
it's funny how often the things we see are not the most important aerodynamic piece: I used to think that diffusers where the strakes but now I realise that the essential part is the slope
that makes sense.
the ex f1 person was yourself lmaooo i can't
Look at the upload date.
Hi, I saw there are small fins in rear bumper in most the car. Are those small fins useful or just for good look?
I am no aero expert, but I know that the "diffusers" you see on most road cars are fake, and they're just decorative, ie, to give it a sporty look. Their diffusers are barely 5cm long. The best I've seen on a road car is the diffuser on a Renault Clio Mk IV RS. If you look at an under body shot on the net you'll see it extends from the rear axle to the back of the car. I don't know how effective it is, but it looks the most effective of all I've seen.
Most enjoy your aero knowledge.
I was watching an old tour de France doco, and in the 90's many teams had wheels entirely covered up in perhaps plastic covers - much like time trial riders (rear wheels especially).
Any how - I'm interested to hear your insight - especially that 10 years later - wheels are certainly not covered.
Whats the deal?
888berg I'm not hugely up on bike aeros, but my understanding was that the full covers give less drag, however have significantly higher sensitivity to crosswind. I believe it was largely a rules change which removed them, although they also are heavier so for rides with hills etc the aero benefit is probably negated by the extra weight. The fact that time trial riders (who are generally less restricted by rules on their bike aeros) still run discs on the rears shows to me that they are still superior for drag.
KYLE.DRIVES
Cheers for the reply - that makes sense :)
how does this explanation help in the case of the RedBull diffuser which cuts off half way
i expect its to only catch the end of the tire squirt coming into the diffuser
I need some advice on a rear diffuser i have for my clubsport which is used for club sprints. how can I contact you and send some pics to you?
+Ed Ward For consulting work, you can contact me at www.jkfaero.com or use the business contact email on my channel page.
Cheers,
Kyle
How fast do u need drive for a splitter or/and defuser to have any value except from cool looks???
Not relevant at all but you remind me of the chap out of Ted that tries to steal him (the teddy), great video!
Since the vortices rotate clockwise on the right side and counterclockwise on the left side looking from behind the car ahead, does that encourage an "inwash" ? Does the direction of spin matter for how good and air skirt the vortex is ? Would the opposite spin on both respective sides be better by encouraging and "outwash" ? What do you think Kyle ?
Peter B The "inwash" is actually the thing the at is causing the vortices if you think about it that way. The strakes are essentially fighting the inwash from both the tyre jet and outside air being drawn into the diffuser, and the direction of the vortices is decided by the crossflow over them. To get opposite spin, the strakes would actually have to be oriented to draw the air inwards, which would be the opposite effect. Think of it as the strakes help stop the crossflow and section off problematic parts of the diffuser, and the vortices (which can entrain flow) act as further barriers near the ground that can stop undesirable flow features migrating across (such as tyre squirt).
Hey Kyle, I saw ford doing some ducting on their new F-150 where they routed air coming at the front into the wheel wells. Can you explain if this is a benefit or detriment?
Colin Terry I honestly can't see how that would be of benefit, unless it is for brake and shock cooling. Thinking about it, that is probably the reason as they are quite heavy so downforce isn't exactly going to matter, and the drag is so terrible on the thing already that that wouldn't matter, but a big truck could always do with cooler brakes and shocks...
Thanks, I guess I never considered that as a possibility. It does make sense now that I think about it. Thanks so much for the insight!
Looking into it, Ford has explained that the system (which they call "The Air Curtain") is supposed to create an airflow that goes in through the front and exits from the wheel well, with the intention that this helps keep outside air from diving into the wheel well and interacting with the wheel, reducing turbulence and drag. Essentially it tries to smooth out the airflow across the side of the car. They can't use the "optimal solution" (fully enclose wheels in skirts) due to practicality reasons, so they're trying to use this ducting as a way to get a similar effect.
i personaly think its not about ''vortex'' but about air flow , if the exit is wider than the entrance , its gonna create suction/downforce at entrance of air , and also drag at the rear to help stabilise the car , and making it go twards the exterior may also help diminish the turbulances coming from the sides .. thats my opignion , i dont really understand the vortex thingy
he's not explaining what the function of a diffuser is, he's explaining the function of strakes ON the diffuser. I think you have it mixed up.
did you not see what the title of the video is?
Just a question sir, at the end of the video you were saying the use of L shape diffuser as it pushes the vortices much closer to ground, then shouldn't be a inverse T shaped diffuser even better than straight edge and L shape.
If yes then why don't are they used in F1 and other motorsports?
Wow just learning about air drag spoilers actual uses besides lookn bad ass.
Tnx bro
And just one more question, if you're able to answer this as well:
Why do LMP1 cars have such a different style rear diffuser and different strakes than F1 cars and other sports cars?
Luke Parsons Mainly when you see diffuser differences , it's due to rules. Don't trust most of what you see on an F1 car, as it's usually just a device to get around a very specific set of rules. In saying that F1 cars have far more rigorous aerodynamics analysis than many LMP cars, so you would expect more complicated flow devices around the diffuser area. Also, the influence of body shape etc should not be underestimated. As such you would expect a large difference between a time attack car, and LMP and an open wheel car.
It appears the Chaparral 2J eliminated all that random airflow. Jim Hall didn't mess around.
Any fan car eliminates this airflow, especially the 2J, since it has that 'Box' format.
What will happen if I put it underneath the bumper I don’t want to put on top of my roof
Does undercar down force negatively affect drag, or fuel economy?
svriderpokey down force does not necessarily equal drag
To both, yes it may, however fuel economy is seldom a factor in racing. The drag is a 'maybe" depending on the design, but may actually improve. In any case the entire purpose of the down force is to improve road grip, improving handling which then allows higher speed maneuvering through corners which then wins the race. Higher overall speed is more important that minor increases in drag or fuel consumption.
In the video ruclips.net/video/pXYJpXKMp_E/видео.html he shows that a simple flat underbody can actually reduce drag, which should improve fuel economy. That does make sense intuitively, as a standard roadcar's inefficient underbody has many areas that interfere with the airflow.
If the underbody has a more advanced design - so that it's not flat and is intended to add more downforce than a simple flat one would - I would expect that there is some tradeoff from an increase in drag compared to the flat. But as with all things aero, that depends greatly on how that interacts with other components. And if there is a way to get 4 pounds of downforce for 1 pound of drag (or whatever the accepted ratio is), then a team would certainly take that option.
So, if you can block the airjet generated by the tyres with one or two strakes, why cars like the ford gt lm gte use up to 8 strakes?
Yesterday, Willem Toet came to my university to explain tha nature of the diffusers and strakes, and clarified the use of them as vortex generators, to take the high energy air from the ground up to the boundary layer...your explanation makes sense though...so I'm a little bit confused right now hahaha
For further information: www.linkedin.com/pulse/how-do-motorsport-ground-effect-diffusers-work-willem-toet
By the way, really liked your videos about aerodynamics. Keep going!
Cheers.
Paddy Lowe lol that's whom he spoke to lol (JOKING)
I have always seen them as tools to soften the laminar flow transition from smooth flowing to swirly behind the car. If you leave flow to go it's way after the flat belly/tunnel, it's going to swirl violently and pretty close to the bodywork. Strakes brake the laminar flow up into sections, creating smaller vortices than transition into high pressure area more easily. I am not making any claims. This was just my layman's thinking. Is there any merit to this theory?
@kyle.drives
What is the height from the ground that the diffuser/strakes/fins need to be at in order to provide best effect?
Why do some diffusers have more strakes than others? Is there a certain "best" number to have?
Luke Parsons Also, is it better if the strakes are straight (as in go back and up at a 90 degree angle) or rounded?
I'm sorry for asking so many questions. haha
Luke Parsons Strake number will vary depending on tyre inflence, ride heigh, flow around the body etc. There is no "best" number to have. I recently designed a full custom undertray for a client where we were running 8 strakes and two horizontal deflectors to control the tyre squirt and ensure extremely high floor efficiency, however the centre 80% of the diffuser only had 2 strakes in it. Normally we try to aim the strakes away from the centre to counter flow ingress, and this results in somewhat of a rounded profile.
Thanks for watching!
so why are there multiple strakes across the entirety of the diffuser and not just one on either side to stop the flow from around the tyre?
One fence along will be fairly ineffective in controlling tyre squirt, as the vortex is not being shared and the squirt cannot be trapped, so you need more than one. In saying that, I often see diffusers with waaaay too many strakes in them and that's largely from people who either don't properly understand their function or are doing it for looks. I am currently doing some consulting for a car that I am putting a strakeless diffuser on as the tyres are a long way from the diffuser so tyre squirt is not an issue.
Thanks for watching!
KYLE.DRIVES sorry *alone not along
KYLE.DRIVES This would explain the C7.R's strakeless diffuser. Though.. that makes me wonder why it looks more like a reversed splitter..
7:34 Sorry but what decides the vortexs' direction?
hsieh811 I was just going to ask that. Do they always form clockwise?
Jesse O'Brien Vortex direction is decided by the direction of flow across the geometry, think of it as flow spilling over the ends. As the diffuser/undertray is a region of low pressure compared to the atmosphere, it will naturally 'suck' the air towards the centre of the car. This creates a flow across the strakes, which will cause the vortices to rotate in the directions I have shown. Does that help?
That makes perfect sense. Sometimes I'm surprised by how simple things are, while other times I'm surprised by how complex these concepts can be. This is one of the simpler times.
As for their rings , they were so high that they were dreadful ; and their rings were full of eyes round about them four .
😀
Love your videos!
So does this mean that if rules permit ideally you should run the side skirts absolutely as low as possible?
Yes, some older f1 cars actually had sliding side skirts!
why dont high end EVs use strakes or fins then? tesla, porsche taycan, the new mercedez eqxx insane flat smooth long diffuser, and so on?
TLDR?
Shame, you're missing out =P
Good video. Sad that the title question isn't answered.
yes it was
antsolja
Where?
maybe if you watch the video all the way through you will see yourself
litterally the entire video is answering the question
I watched the whole thing. What do you think why I say it?
You will now say bla bla. So tell me a point in the video, where it's answered!
so you just cant be bothered to watch the whole video.
just to shut your adhd ass up il give you the short version: the strakes are there to create small vortexes near the ground to stop air being bushed into the diffuser by the tires and ruining the airflow.
Why do you spend so much time telling us what they don't do and what they aren't for? I don't even know what the point is you spent so much time explaining extra stuff I don't even know what the lesson to learn here is.