Flow Viz Paint – What is it and how does it help aerodynamicists learn more?

Flow Viz Paint – What is it and how does it help aerodynamicists learn more?


This video is brought to you by Squarespace
– the easy solution to running your own domain, website or online store today. Most of the research and development that
goes into sculpting and refining the aerodynamic shapes of the various parts of F1 cars is
made in the wind tunnel and in sophisticated computer models called computational flow
dynamics or CFD models. Make no mistake, this is where the majority
of the hard work that goes into designing and testing aero parts like wings and diffusers
takes place. But when the car hits the track there’s
a big opportunity for some final aero checking and verification. One of the ways teams can
do this is with the use of flow visualisation paint, or Flow Viz.
You’ve probably seen Flow Vis paint used on the cars in practice or testing sessions.
The most eye catching use recently was when Williams absolutely covered their car in various
colour blocks of Flow Viz to try and solve some of the mysteries of their misbehaving
chassis. More typically, though, Flow Viz is seen used
sparingly, precisely and in specific areas of the cars. You might see it on the front
wing, over diffusers, bargeboards, etc. So what is Flow Viz paint? How does it work?
And how does it help engineers and analysts understand their cars better?
The main idea of Flow Viz paint is to show the airflow patterns that manifest along the
bodywork of the car as it drives at speed. These flows are normally invisible because…
well, have you seen air lately? Exactly. No, you haven’t.
Flow Viz is a pretty simple product. It’s just a powdered dye suspended in paraffin
or kerosene or a similarly light oil. By suspended, I mean the dye sits happily in amongst the
oil once stirred but will eventually sink and separate from the oil with time. The oil
is just a medium to keep the dye flowing and free.
The useful thing about this mixture is that it doesn’t dry particularly quickly when
it’s all globbed together so you can splosh it liberally over the areas you want and the
paint will continue to run and flow as you drive the car at speed through the air.
A lot of normal paints would dry or stick around the areas you painted them and not
do anything particularly useful. The flow of the air around the car as it drives
will push the oil – and therefore the dye – along the surface of the bodywork all free
and flowing. But paraffin evaporates fairly readily and this will leave the dye behind,
stuck to the bodywork in all the flowing shapes its made in the airflow.
The aerodynamicists can then take photos of the car once it’s parked back up in the
garage and check to see if the paint patterns show the results they’d been expecting.
You’ll often see very brightly coloured dyes that stick out against the bodywork so
they can be easily seen when photographed by the team. But the dye itself may also be
fluorescent, meaning it will show up much more strongly under UV lighting. So if you
see Flow Viz that seems a little faint and unclear, the chances are the paint will look
a LOT more striking back in the garage under the right lights.
Now – importantly – the point of Floz Viz paint isn’t really to gain much quantifiable
or precise data about the aerodynamics. Instead, it’s a fairly quick and dirty method to
double check that the computer models and wind tunnel tests corroborate with real-life
running. Teams still can’t fully replicate the many
eccentricities of the real world from inside their own HQs (though Lord knows they try),
so a full scale run on a real track is the final, definitive test for that new front
wing or whatever that they’ve been developing behind the scenes.
Did it behave as expected? Does it differ from the old spec front wing in the way they
intended? Or is it giving some strange flow behaviour that you need to analyse and double-check?
This is the benefit of flow viz in the real world, though it has of course been used in
wind tunnels for many, many years – way before it showed its head in testing and practice.
Now, there may be extreme cases, like Williams this years, where teams just want to evaluate
the whole package and record lines over the whole chassis. You can do that, if you want,
but you really shouldn’t ever be at that point with a car halfway through a season.
OK, so you’ve slapped a load of flow viz paint on the part of the car you want to evaluate.
Your driver has done a lap or two and brought the car back to the garage.
How do you interpret the colourful mess left all over the carbon fibre?
Well, firstly – as outsiders, we’re never sure exactly what the aerodynamicists are
looking for in any given tests, particularly when testing one part against another. They
may be looking for any number of characteristics so we can’t speak to the result of any particular
evaluation. That being said, here’s what happens to
Flow Viz paint under various, important circumstances. Firstly, we can see clearly if there is a
strong, clean, smooth air flow along the bodywork, as opposed to a dirty and turbulent flow.
Just using a wing profile here as an example (as it’s easy to visualise): smooth air
flow will run nicely along the surface in good, coherent lines all running together
from beginning to end. You’ll see this in the Flow Viz pattern
too. Smooth, coherent lines just like someone took a nice, quality paintbrush and drew a
clean stroke across the bodywork. Satisfying to look at.
Smooth airflow is desirable because it’s predictable and stick to surfaces. It also
continues to be easily manipulated by further aero devices downstream as long as it continues
to stay coherent and flowing. Turbulent airflow is where the air gets chaotic
and starts to misbehave in twists and curls and acting in an unpredictable, blustery way.
This is often undesirable, particularly along the bodywork, which is where Flow Viz makes
its measurements. Turbulent flow will throw the paint into chaotic
splotches. You may see pools of paint gathering together in seemingly random patterns, distorted
waves of colour and other messy patterns. Just generally, paint gathering in anything
but those nice smooth lines we just saw is an influence of turbulence.
Another thing to look for is where the air flow is attached to and detached from the
bodywork. For the most part aerodynamicists design the
shapes of wings and other body parts (particularly aero devices) to keep the air flow attached
to their surfaces. This means the air sticks to and follows the
surface closely. At high speeds it’s easy for the air to
fly away from the surface if that surface changes direction suddenly and this is called
airflow detachment. Detached airflow is mostly not desired as
it greatly reduces downforce and increases the risk of turbulent further down the body.
But whatever kind of attachment pattern you’re looking for, you can spot it with Flow Viz,
for the most part. If the airflow is attached it will carry and
spread the dye along the body of the surface. A nice, strong, continuous attached flow will
show itself by trailing a lot of dye along the area of the attached flow.
If the air tends to detach from the surface it won’t be able to drag the Flow Viz paint
and you’ll see gaps on the bodywork with a distinct absence of paint.
There is a limitation here, however. Often airflow detachments will occur at higher speeds
and if the paint has already been allowed to flow through the lower speeds as the car
accelerates up to top speeds it may be very difficult to spot that this is happening from
Flow Viz alone. In this shot of the Red Bull rear wing we
can see some detachment from the underside here among otherwise strong, attached flows.
Here is looks like there’s some detachment though it may just be an unpainted area.
This show of the McLaren diffuser shows where the airflow sticks and detaches to the underbody
shape. Here, of course, some detachment may be part of the design.
Again, we don’t know what tests are being run so we can’t overstate what we’re looking
at but we can take a lot of interest in the areas being studied.
For example, Sauber here are clearly evaluating how the air flow disrupted by the front wing
continues to behave all the way down the side of the car.
Here the McLaren is checking how the air front the front wing flows through the bargeboards
and turning vanes. Here it looks like McLaren are specifically
evaluating the efficiencies of the airflows on the left and right sides of their car separately,
to have a look at the differences on a specific track.
Flow Viz paint is a striking but limited method for confirming aerodynamic expectations on
track. Teams will often get a lot more data from their wind tunnels and these pitot tubes
structures but Flow Viz continues to be a quick and easy way to sign everything off. And speaking of quick and easy ways of getting
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100 Comments

  • Koen Prud'homme van Reine says:

    Great vid as always! Just one question, where was the mini q%a? I enjoy those a lot.

  • kovi17 says:

    Great work, as always!

  • One Two says:

    Nice transition

  • Aslamnur Fikri says:

    Flow viz has one big disanvantage: engineers from rival team can clearly see its aerodynamic pattern and analize it by photos

  • Redbull Racingteam says:

    Thank you so much

  • Green Shell says:

    Thanks for covering this Chain Bear. I was just gonna ask you this since I saw Williams paint their car back at the German grand prix.

  • Vectored Thrust says:

    You know it's really bad at Williams when they were like

    "Ok, so what parts of car is giving us problems?"

    "All of it. Just…all of it. Put flow-viz paint everywhere"

  • Chris A says:

    Bravo another fantastic video! Fresh well delivered objective information, fans deserve access to.

    Liberty media should be sponsoring you.

    Ps do you think they should they bring back tyre manufacturer competition.

  • zzzonked says:

    Didn't think this topic was going to be very interesting but Chain Bear has done it again! Well done mate 🙂

  • Teilo How says:

    cheeky smooth segue into the sponsor 😉

  • elvisg7 says:

    Wow, this video was incredible Chain Bear. Thank you. I always love that you take complicated things about F1 & make them so digestible & easy to understand, but this was even more. It took one of those things I always just dismissed as F1 black magic & made it easy to understand. I can't believe I learned this much about interpreting Vlow Viz. That's incredible.

  • HaloReachsquad6 says:

    THANK GOD YOU DID THIS VIDEO

  • Wheatley says:

    I think ive watched every single video of yours and forgot to follow. Here have my follow 🙂 Great work btw !

  • ihathtelekinesis says:

    Fantastically insightful as always, and you’re approaching Wendover levels of transition into the sponsor at the end!

  • Jimmy De'Souza says:

    I would like to see the difference around a track between an F1 and a car which is mechanically the same but aerodynamically a brick.

    I mean I know the difference will be huge, but how huge? 20%? 50%?

  • Emperor McCarthy says:

    time to bake some cherry pies

  • gruffydd gozali says:

    What are the peton structures?

  • Felipe Jensen says:

    Awesome Video!

  • Balázs Orosz says:

    s e l l o u t

  • Vaes Joren says:

    I don't know if this is the same in aero, but in my field (micro and millimeter wave electronics) we also use a lot of simulation, and the bulk of the work is done there. And there has been a significant shift over the last few decades – where it used to be that simulation gave a first starting point, and then did a lot of the actual design with measurements, now we do all the design in simulation, and only measure to verify our results.

    This also means that sometimes we will test (esp at the beginning) designs that aren't good, but are there to emphasize a certain behavior. This allows us to really see how good our simulation matches reality and give us better models.

  • UmbreonDusk says:

    So this is the rare case where watching paint dry can actually be entertaining 😀

  • DudeOnly GamingAndOtherStuff says:

    Or probably williams wanted to look as colourful as Benerton

  • MrBrN197 says:

    0:16 CFD usually means Computational Fluid Dynamics, I am not sure; I might be wrong. maybe it's also referred to as Flow Dynamics.

  • JW says:

    Nice to see youve got a sponsor.. hard work pays off

  • Jack Collett says:

    How do air rakes work?

  • Isaac Stevens says:

    Odd question: Will there ever be any videos on other racing series? Sure, many of the concepts of overtaking, and clean/dirty air, and tires and brakes carry over very well, but I'm curious if you'll ever look into the rules, or technical aspects specific to IndyCar/Rally/NASCAR/Drag/WEC.

    I love the content you put out and would be interested in seeing your take on other styles of racing. Thanks.

  • Gerardo Trejo says:

    F1 Science yeahh!!

  • Chain Bear F1 says:

    CORRECTION CORNER:

    CFD = Computational Fluid Dynamics. I think I'd just been saying 'flow' so much my brain broke.

  • aaronj84 says:

    The qualifying in Hungary with the rain showed some really cool patterns of the water coming off the back of the cars in vortices. You could really see how high and wide the rear wing and airflow kicked out the dirty air behind the car. God’s flow viz

  • Stephen Whiddett says:

    CFD = Computational Fluid Dynamics

  • da_destroyer says:

    Is it possible I can make flow wiz paint at home? I saw that all i need is oil and dye but like what type of oil and what type of dye is needed?

  • Xuanyu Lyu says:

    Flow-viz is a good and necessary tool for validating the on-body surface flow field, however not being able to reflect specific data is not its only disadvantage. Flow-viz merges the surface flow field under all circumstances, including straight line, turning (yaw, when the air blows the car at a changing angle while turning), braking and accelerating (the diffuser may have flow reattachment during braking but delibrate flow separation during high speeds) and roll. In technical terms, flow-viz reflects mainly a 'steady' state, but is unable to tell the 'instant state problems', happening only during a certain stage of the car's operation envelope, and that's why flow-viz can only be used as a crude method of aero correlation on track. In addition, the 'grilling grid' is used to measure off-body flows at every specific moment, especially tyre wakes and vortices, to further detect instant problems and the car's aero robustness. 😉

  • Arti Qormemeti says:

    Computational Fluid* Dynamics.

    Great video btw.

  • Kakashi Hatake says:

    ah so that's what was on the Force India front wing.. I was wondering why the sudden change to green

  • thosecarkids says:

    Did Squarespace sponsor this video? 😂 JK Chainbear you the best.

  • Roland Lawrence says:

    do the aero industry use flow vis paint as well? seeing that many f1 aero's have a synergy with the aircraft industry…

  • Thauã Aguirre says:

    You can also apply drops of it to better analyze flow at slower speeds.
    The tricky part about this paint is getting the viscosity just right for the speed you have to analize. Or maybe my mixes aren't quite right. The F1 high speeds make it not a problem, but I work with very slow speeds in competition RC planes, so too viscous and it doesn't flow while upseting the airflow itself (I use spots instead of lines. Will definitely try lines next time). Too flowy (too much kerosene, basicaly) and it dries too quickly.
    Also, it's the kerosene that evaporates. The parafin (I use literaly grounded candles. Am I doing something wrong? The kerosene should dilute it) is what helps the dye stick.
    Also(2), food colouring works for the dye.

    I tried using powdered chalk first. It sucked. The trails are too faint. Maybe because my entirely empirical mix is wrong but maybe because the chalk flakes are too big. Powdered colored candles do not give enough dye. Methylene blue (engineer's blue) is said to work the best, but I haven't tried it. With food dye, I have a myriad of colors to choose from.

    Oh, another problem that I can't replicate on CFD is Flutter (Yes, I'm very entry level when it comes to CFD. But I'm good with fluid mechanics and coming up with experiments). Basically when the wing structure is not rigid enough and jumps around like mad, especially when it combos torsion and flexion. It disrupts the airflow, often producing some turbulence, and can even stall the wingtips or even break the wing through fatigue. I haven't faced it yet, but it's most likely going to show when I start researching winglet designs.

  • ericsbuds says:

    interesting! I couldn't figure out what they were using it for, so thank you!

  • Burning Tyre says:

    Thank you very much! Waiting for a video about the aero sensors(like on Sauber 6:04)

  • Shatrunjay says:

    A seperate video on those tube grids?

  • Josh Eichholz says:

    Brought to you by: Williams has no clue what they’re doing

  • slikrx says:

    Neat vid. Mark Priestly did a neat vid on this as well.

  • Mucky Vagrant says:

    Would be great to have some mid-season analysis of how Ferrari have now supposedly got a better package than Mercedes. I'm a fan of both Seb (great bloke) and Lewis (because patriotism) and the season is on a knife-edge. Where do the strengths lie? The man? The machine?
    With cars developing and evolving between races more than they did in a season when I first got into F1 it's bound to be hard to keep up but if Ferrari have an edge… what is it? Or even what do you think about it?

  • tjockiskatten says:

    No! Another good channel ruined by anoying squarespace-sponsoring!

  • BASIR KHAN says:

    very informative

  • MRMF1 ALT says:

    2:12 why is there a year 6 disco rave? wtf!

  • Bpendragon says:

    I mean, I can see the air right now. There's so much smoke And in some cases even see things move through it.

  • Gavst3r says:

    Threw some Dulux on my ex gf’s car to achieve the same thing…………. your video was too late……….. I’m due in court next week.

  • Sami Kalla says:

    U guys never disappoint, brilliant video as always.

  • Ramdhan IXII says:

    omg at last this is what i needed
    great job chainbear

  • James Wright says:

    The main thing you're missing in your explanation is talking about boundary layers (which I don't blame you for as it's a but of a complex subject, especially if you try to explain why boundary layers matter). This kind of visualization is fantastic for determining where your boundary layers transition from laminar to turbulent. This transition is can be used for determining how "hard" you are working the air and how close the air is to detaching.

    This is especially important because A) CFD has a difficult time determining these transitions (there are models, but they have to be calibrated and need to have some baseline, which flow viz can be used for) and B) the transition on the 60% scale models isn't valid as the transition is a very scale dependent phenomenon (and Reynolds number scaling won't quite be accurate either).

  • ChaotikFPV says:

    You even made a quality advert for Squarespace that was compelling and made me actually think about whether i needed it in my life or not. I don't, but it still made me think.

  • Benoit Said says:

    could you make a video on the technology behind onboard cams ? how they wipe the insects during the race, the regulation around it (are they compulsory ?), etc. I think it could be an interesting topic, i haven't found any info

  • AlphaAce15 [ART] says:

    Somehow, I feel like this channel explains physics better than Engineering Explained.

    Sorry EE.

  • Thierran Tavakoli says:

    I just have a random question.

    If Williams' 2018 car is such a dog that it needs flow-viz paint for the entirety of the car, why not run the 2017 car for the rest of the season? Surely it give an equal chance of scoring some points or at the very least they'd still be in the same situation they are now. Is there a regulation against it?

  • 🅱 says:

    10/10 would F1 again

  • Lord Kirtash says:

    Thanks for another great video.

  • Bahamuttiamat says:

    Computational FLUID dynamics. Not flow…

  • sankimalu says:

    So basically, ignore art class at your peril? Fascinating! It is like Holi but for cars…

  • Mutualist Anarchist says:

    Literally every YouTuber is sponsored by squarespace

  • Tomas says:

    Halfway through and this vid was a lot better than I thought it was gonna be!

  • Jasper Li says:

    How was you WTF1 GP experience?

  • Stark Raven says:

    The development behind F1 is intriguing. The racing has some catching up to do, though…

  • joek81981 says:

    What was that bit at the end? I can't make out what he's saying. It looks like chicken coops nailed to the bodywork? That looks crazy! Do THAT video!

  • Horstan Andamir says:

    This patreon list grows and grows

  • adib z says:

    Im throwing paint to my car right now

  • Jayden Rice says:

    "When did you last see air" I saw liquid oxygen yesterday

  • BariumCobaltNitrog3n says:

    flow viz=gut check

  • Asdayasman says:

    What if this is peacocking? Or whatever the equivalent directed at other males is called.

    The teams are plopping this paint on their cars and getting these beautiful smooth lines, and the other teams are looking at those lines like "oh fuck look how good their car is".

  • escaperoute2 says:

    Williams was testing the 2019 spec front wing on their car after the Hungary GP. They covered their entire package in flow viz because the new front wing will change the airflow everywhere along the car

  • Meap says:

    What is ERS ?

  • Wolf says:

    In the olden days , they used wool tufting. Small strings o wool attached to the car. These would move with the airflow and give a good representation of where the flow was separating.

  • Tomas Kocman says:

    Hi guys:-)
    Great video, appreciate & send you couple of bucks thru Patreon.
    BUT!
    Would you mind guys … for us non-native speakers
    SPEAK MORE SLOWLY PLEASE.
    It is sometimes REALLY DIFFICULT to understand:-(
    And/or subtitles? Just like ted.com (google subtitles DEFINITELY does NOT help).
    Thanks again!
    Tk.

  • Greg Brown says:

    Thanks Chain Bear

  • Brad Adams says:

    I would love to hear about super license and how you get one and what happens with points on the license.

  • TheHeavyshooter says:

    I wonder how the new engines will sound with 3k rpm extra?

  • Lebogang Tooka says:

    chain bear F1 thank you for the videos

  • eddie booth says:

    just a possible small correction you sugest that smooth air flow sticks to the body more however this isnt true sometimes turbulent air is induced because it sticks to the body more then smooth airflow

  • Everson Bernardes says:

    Smooth flow into that sponsor 😀

  • Jack Curtis says:

    Williams team: "Aw man, how are we gonna test our aerodynamics?"
    employee comes back from the gay pride across the street
    Williams team: "That's it!"

  • Nick's Stuff says:

    Good job, now I want to try that on my touring car

  • Mishkatul Anwar says:

    Dude you forgot to add photos in the last few minutes

  • Midgetbar maid says:

    I have never seen this. This is such a weird concept!!

  • Sean Silva says:

    Please cover suspension in a future video.

  • Winston Hale says:

    For a technical video about aerodynamics, I'm surprised the word "laminar" wasn't used

  • Tetra says:

    To be fair, Williams was testing a 2019 spec front wing. It was probably more of a quick way of figuring out how viable their current design is for next year

  • Admiral Percy says:

    Wait. Are you saying paraffin is the same thing as kerosene?

  • Alfonso Muñoz Sahr says:

    Did not knew about this! Thank you!

  • Vag.Cho/10 says:

    My realy first thoughts were that i didn't saw well… Why it has to be green in a McLaren…

    Afterwards, i saw your video…
    So, it was useful…

  • Bruno says:

    It's actually not true that laminar flow sticks to surfaces all that well, in fact turbulent is the best at delaying flow separation.

  • Myster1ous says:

    But how do they wash it off?

  • DULES 152 says:

    mannn, that outro is nuts!!!!
    someone knowa the name or is it exclusive for the channel??

  • Tony Bucca says:

    What studies have been done vis a vis golf ball dimples and body work?

  • egj1975 says:

    The quality of this channel is stunning. Great work!

  • Ivan Lipkov says:

    I'll do it with my car. Want to know who the air goes.

  • Dadul Ludad says:

    Paraffin and kerosene are not the same, btw

  • AffirmingFoil7 says:

    Does anyone know where to buy it?

  • Matt says:

    you legit could have just said "It does exatly what it sounds like" lol

  • Jari Beitler says:

    You said the smooth airflow (I assume laminair?) sticks better to the surface, but I thought turbulent air sticks better to surfaces with the downside it increase the drag. For example on airplane wings it is desired to have a turbulent flow, because is it increases the lift. Is there something I have been missing?

  • mobile pliot war wings says:

    If dan went to redbull

    Double torpedo

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