Hi Wouter, thank you for doing this video. I have a Beetle 67 here in Brazil and I am very interested in how I can improve the airflow to the engine. As you know, the air-intake is located just under the rear window. Driving in the city I never had a problem with overheating, but on the highway on longer journeys the temperature easily gets critical. Can you tell me at what speed the air starts detaching from the rear window, and would vortex generators drastically improve the air-intake at higher speeds? Best regards, Kris
Hi Kris, good question! We found separation to happen quite high, at the top of the rear wind shield. To keep the flow attached all the way to the air intake is very difficult, I would say. Alternatives include keeping the engine hood open (some put a hinge at the bottom, instead of the top, and leave a 10cm opening while driving!), or air intakes (with air channels to the engine) at the side windows (at the end, you now probably have some small cooling vanes for the interior). An active fan could also be an option!
Oh that's too bad. I would like to see a wind tunnel test with vortex generators though. I could only find one without here on youtube and as you say, the air starts separating quite high on the rear windshield.
@@krispaul2939 Hi Kris, perhaps you can experiment yourself with Vortex generators? As you can see in our movie, the tufts down low still improve, but not by a huge amount. Might still be worth it!! Perhaps log your engine temperature, and compare different cooling concepts?
I've installed the vortex generators, let's see if it yields anything, otherwise I'll look into your other suggestions, but it would be nice solving this without too many modifications. What happens if you install one more row of vortex generators below the first one? would that force the airflow to follow the curvature down to the air intake better?
@@krispaul2939 Hi Kris, hm, good question. When I experimented on the beetle, moving the row 5cm upstream or downstream already made a huge difference. It's a matter of making the boundary layer turbulent enough, just enough upstream so that you post-pone the separation point. A second row could make sense if the flow becomes laminar again in between, but perhaps then this indicates that the first row is too much upstream? You'll have to experiment, like you say! And there is only so much negative angle the flow can take before it separates at a certain speed, vortex generators or not.
This concept of vortex generators is really fascinating for me especially when Wouter Remmerie explained it so beautifully. Honestly it put a smile on my face when I saw the significant elimination of reverse flow by using these indeed very High tech paper vortex generators. Thank you Mr. Remmerie. Keep shaping the Air.
Clear, concise, informative and fun! This is a GREAT channel and the presentation formula is one of the best on the Internet. This is quickly becoming one of my favorite TH-cam sites. Thanks for the excellent efforts.
Awesome channel, I'm a comercial pilot and flight instructor and yet, this is the first time I actually get to see the effect of vortex generators with my own eyes!
Thank you very much Francisco! What plane do you fly? Vortex generators are sometimes used on planes as well, usually to delay stall - see this link for example: en.wikipedia.org/wiki/Vortex_generator
@@AirShaper I've flown several planes (pa28, pa34, be76, c172, pa30, pa23, etc) including a Cessna Citation with an upgrade with vortex generators, the approach speed was as slow as 105 kts. But I'm currently flying a Britten Norman BN2-A "Islander" in the Galápagos Islands. I'll take a look to your other videos!
@@AirShaper Definitely, it's another kind of commercial aviation. Small or light airplanes make the part of "flying" more interesting, you actually get to fly and navigate like old school pilots. In the case of the Islander, the flight controls are driven by pulleys and wires so you actually get to feel the buffet prior to the stall, and in Galápagos, you only use VOR's, DME and NDBs as a primary source of navigation! Its a great experience
What would be the effect by placing AirTabs on the rear trailing edge on the roof top of a pickup truck 🛻 which has a significant curvature by the back window . I’m doing some test on a 2021 Toyota Tacoma with a tunnel covering on the bed.
Hi Hans, we've had that question before! The AirTabs, from what I understand, have the aim to energize the boundary layer just before the edge and "pull" the flow inward, I would think. On large trailers, that makes sense, as you want to contract the wake. On a pickup truck, you'd probably have to analyse whether contracting the flow will make it hit the loading bay or not. Also keep in mind that the AirTabs also add drag locally, so you need to gain even more in other locations (like in the wake) before they become useful. Last but not least, their performance may depend on the angle of attack, on speed (and thus Reynolds number) and on flow quality of the air in front of the vehicle (if you're drafting another vehicle, likely their effect will be different). So plenty of scenarios to test :)
The intake of the engine is far down - I would guess the flow still detaches before it reaches that point. Perhaps adding a well hidden air scoop to feed slightly higher pressure air to the intake would be nice? :)
That would indeed have been great! I didn't do such a test (not enough time / measuring tools for fuel consumtion / ...). Perhaps one day if we repeat this test we can do this!
I suppose these would also work on the sides of boxy cars (wagons, hatchbacks), vans and trucks I might try these to see if they can be used to keep the rear window cleaner for longer.
This has been a point of discussion before! Vortex generators can help a lot to energize a flow upstream of a "negative curve" - the extra momentum helps to keep it attached to a gradually inward curving surface. When you look at abruptly changing curves, like a 90° bend, the story is different: the goal, then, is no longer to keep the airflow attached, as it will separate anyway. But in some cases, it can still help to add vortex generators to energize the flow and have it shoot slightly "inward" after the 90° bend - contracting the wake a little. You may want to have a look at AirTabs, which are applied at the boxy end of trailers. Not sure which official proof they have, but definitely interesting!
Hello AirShaper, I am doing a High School project on vortex generators and delaying flow separation. In my case, it is on a model wing rather than a Beetle. I was wondering how I should position my VGs and tufts/strings to get representative results. Should the VGs be directly in front of the tufts? Should they be staggered between them but slightly ahead? Or should it be more randomised? What do you think is the best approach here?
Your VGs should be positioned just ahead of the flow separation. Your tufts should be positioned wherever you want to see the flow pattern (so use many of them perhaps :) )
Hi THEDnARACER, At speeds of 130 mph aerodynamics are by far the most dominant source of resistance (easily over 80%). The vortex generators can make a difference for sure, to reduce drag for example. But careful application is advised. Also, they influence the air that is fed to any rear wing for example, if you have one! Kind regards, -The AirShaper Team
Fast moving air stuck to the window will create suction and the vortex generators create drag. This video misses the point completely: for you, reducing drag is more important than clean windows. A spoiler above the window to separate the airflow will increase the pressure on the rear window and actually push you forward - actually reducing drag
Vortex generators utilize the same effect that dimples on a golf-ball utilize, except on a golf ball we have to cover the entire ball because we don't know where the front and back is because the ball is spinning, whereas on a car or airplane we know where the front and back is so we only place them strategically.
Hi Erik, thanks for the comment, that is entirely correct! In theory, you could make a golf ball fly even further if it's orientation would be constant 🙂 for cars, this is almost true: sidewinds, upstream turbulence etc can alter their behavior and thus the impact in drag.
@@isaacchiappetta4042 It would indeed! At the moment, we're aiming to spread our attention across various segments. If we ever revisit the beetle, then we can certainly do this :)
Good video! The facts about functional VGs in general automotive applications has become so distorted amidst a decade of EVO wannabees. You don't need a wind tunnel to determine the point of separation, but you still need to "test"(w/tufts and/or powder) to determine an optimal mounting position.
Thanks Micro Air! Indeed, a number of cases where vortex generators were applied on iconic cars have triggered others to apply them as well, also on cars where they're less relevant. These days the back of cars is so gently inclined that VGs are usually not required, as there is little seperation before you reach the trunk.
Depends on the model, if the slope of the rear window is quitr 'negative' and separationnis expected then it might make sense. If it's upstream of an abrupt cut-off of the roof line (like the latest model) then the air will separate anyway and vortex generators make no sense. A cfd analyse of the base model will provide that insight!
@@bscgarage If I'm looking at the correct MX5, then it's the one with the abrupt end of the roofline: so you would have flow separation there anyway. So then vortex generators wouldn't help, in my opinion.
Hi Paul, a pickup truck typically has quite an abrupt drop after the front cabin. So there's not really much of a "negative curve" going on there, so I would guess vortex generators have less of an effect. But it would definately be worth the test :):)
Hi Eric, indeed, it's possible that by pulling down the airflow you actually generate more drag. Another aspect is the "stability" of the flow pattern, which can also be influenced (in both a good or bad way) by influencing the separation location with vortex generators.
Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure so fast moving air stuck to the Beatle's rear window will create suction (increasing drag) and the vortex generators will also directly create drag. This video misses the point completely: the Beetle needs a spoiler above the rear window. If the angle of the rear window was flatter, then the spoiler could be lower like on a Porsche 911 but a Beetle needs separation above the rear window.
Hello Jeremy, just like the Bernoulli's principle is not enough to explain how wings work, it is not enough to explain the complex flow structure we're looking at here. Yes, a small spoiler creating a separation point could be a valid option to reduce drag, just like the coda tronca cars from the past. But it's not the only option: the vortex generators themselves indeed create extra drag locally. And yes, they speed up parts of the flow close to the window. But that is not the only aspect, they decrease the large wake zone at the rear of the car, which is creating a large suction effect as well. As you know, similar effects have been demonstrated to work on golf balls (the dimples). Hope you agree to this explanation, let me know your opinion.
Jeremy Parsons wrong. bernoulli's principle will create lift on the car, not drag. with increased flow attachment the car will have increased lift according to bernoulli's principle. this could be offset with a trunk spoiler which could be smaller because the increased attached flow increases the efficiency of the spoiler. the reduced low pressure wake behind the vehicle will reduce overall drag. be careful when applying physics there are often multiple effects to consider.
It's indeed not essential to drive the car. And on modern cars, there is no need at all because the base shape is streamlined enough to avoid separation without vortex generators. But for some applications (in sports, aviation and cars) it can be useful to optimize for efficiency, range, top speed, ...
![Wings vs Spoilers & Vortex Generators [Car Aero Guide]](http://i.ytimg.com/vi/oo4EjuEgmsw/mqdefault.jpg)
Hi Wouter, thank you for doing this video. I have a Beetle 67 here in Brazil and I am very interested in how I can improve the airflow to the engine. As you know, the air-intake is located just under the rear window. Driving in the city I never had a problem with overheating, but on the highway on longer journeys the temperature easily gets critical. Can you tell me at what speed the air starts detaching from the rear window, and would vortex generators drastically improve the air-intake at higher speeds? Best regards, Kris
Hi Kris, good question! We found separation to happen quite high, at the top of the rear wind shield. To keep the flow attached all the way to the air intake is very difficult, I would say. Alternatives include keeping the engine hood open (some put a hinge at the bottom, instead of the top, and leave a 10cm opening while driving!), or air intakes (with air channels to the engine) at the side windows (at the end, you now probably have some small cooling vanes for the interior). An active fan could also be an option!
Oh that's too bad. I would like to see a wind tunnel test with vortex generators though. I could only find one without here on youtube and as you say, the air starts separating quite high on the rear windshield.
@@krispaul2939 Hi Kris, perhaps you can experiment yourself with Vortex generators? As you can see in our movie, the tufts down low still improve, but not by a huge amount. Might still be worth it!! Perhaps log your engine temperature, and compare different cooling concepts?
I've installed the vortex generators, let's see if it yields anything, otherwise I'll look into your other suggestions, but it would be nice solving this without too many modifications. What happens if you install one more row of vortex generators below the first one? would that force the airflow to follow the curvature down to the air intake better?
@@krispaul2939 Hi Kris, hm, good question. When I experimented on the beetle, moving the row 5cm upstream or downstream already made a huge difference. It's a matter of making the boundary layer turbulent enough, just enough upstream so that you post-pone the separation point. A second row could make sense if the flow becomes laminar again in between, but perhaps then this indicates that the first row is too much upstream? You'll have to experiment, like you say! And there is only so much negative angle the flow can take before it separates at a certain speed, vortex generators or not.
This concept of vortex generators is really fascinating for me especially when Wouter Remmerie explained it so beautifully. Honestly it put a smile on my face when I saw the significant elimination of reverse flow by using these indeed very High tech paper vortex generators. Thank you Mr. Remmerie. Keep shaping the Air.
Thanks a lot, we'll do so!!
Clear, concise, informative and fun! This is a GREAT channel and the presentation formula is one of the best on the Internet. This is quickly becoming one of my favorite TH-cam sites. Thanks for the excellent efforts.
Hi Jeff, thank you for the awesome feedback! We do our best!
Kind regards,
The AirShaper-Team
Awesome channel, I'm a comercial pilot and flight instructor and yet, this is the first time I actually get to see the effect of vortex generators with my own eyes!
Thank you very much Francisco! What plane do you fly? Vortex generators are sometimes used on planes as well, usually to delay stall - see this link for example: en.wikipedia.org/wiki/Vortex_generator
@@AirShaper I've flown several planes (pa28, pa34, be76, c172, pa30, pa23, etc) including a Cessna Citation with an upgrade with vortex generators, the approach speed was as slow as 105 kts. But I'm currently flying a Britten Norman BN2-A "Islander" in the Galápagos Islands. I'll take a look to your other videos!
@@fjng1 Oh that's really cool! Lot's of smaller planes, I guess you have lots of contact with the passengers, plenty of interesting stories :)
@@AirShaper Definitely, it's another kind of commercial aviation. Small or light airplanes make the part of "flying" more interesting, you actually get to fly and navigate like old school pilots. In the case of the Islander, the flight controls are driven by pulleys and wires so you actually get to feel the buffet prior to the stall, and in Galápagos, you only use VOR's, DME and NDBs as a primary source of navigation! Its a great experience
Mashaa Allah that explanation was really good.Thank you very mcuh sir.
You're very welcome!
What would be the effect by placing AirTabs on the rear trailing edge on the roof top of a pickup truck 🛻 which has a significant curvature by the back window . I’m doing some test on a 2021 Toyota Tacoma with a tunnel covering on the bed.
Hi Hans,
we've had that question before!
The AirTabs, from what I understand, have the aim to energize the boundary layer just before the edge and "pull" the flow inward, I would think.
On large trailers, that makes sense, as you want to contract the wake.
On a pickup truck, you'd probably have to analyse whether contracting the flow will make it hit the loading bay or not.
Also keep in mind that the AirTabs also add drag locally, so you need to gain even more in other locations (like in the wake) before they become useful.
Last but not least, their performance may depend on the angle of attack, on speed (and thus Reynolds number) and on flow quality of the air in front of the vehicle (if you're drafting another vehicle, likely their effect will be different). So plenty of scenarios to test :)
would we see an improvement in performance, regarding air intake in to the engine??
awesome video
The intake of the engine is far down - I would guess the flow still detaches before it reaches that point. Perhaps adding a well hidden air scoop to feed slightly higher pressure air to the intake would be nice? :)
Mile per gallon change at constant 65 miles per hour for 100 miles Comparison. Would be great. Thanks
That would indeed have been great!
I didn't do such a test (not enough time / measuring tools for fuel consumtion / ...). Perhaps one day if we repeat this test we can do this!
I suppose these would also work on the sides of boxy cars (wagons, hatchbacks), vans and trucks
I might try these to see if they can be used to keep the rear window cleaner for longer.
This has been a point of discussion before!
Vortex generators can help a lot to energize a flow upstream of a "negative curve" - the extra momentum helps to keep it attached to a gradually inward curving surface.
When you look at abruptly changing curves, like a 90° bend, the story is different: the goal, then, is no longer to keep the airflow attached, as it will separate anyway. But in some cases, it can still help to add vortex generators to energize the flow and have it shoot slightly "inward" after the 90° bend - contracting the wake a little. You may want to have a look at AirTabs, which are applied at the boxy end of trailers. Not sure which official proof they have, but definitely interesting!
very informative video - cheers!
Thanks Clint2jz!
Hello AirShaper,
I am doing a High School project on vortex generators and delaying flow separation. In my case, it is on a model wing rather than a Beetle. I was wondering how I should position my VGs and tufts/strings to get representative results. Should the VGs be directly in front of the tufts? Should they be staggered between them but slightly ahead? Or should it be more randomised? What do you think is the best approach here?
Your VGs should be positioned just ahead of the flow separation. Your tufts should be positioned wherever you want to see the flow pattern (so use many of them perhaps :) )
Hi i wanna ask if i need an aerofoil shape for a vortex generator since im trying to seal the edges of my mini car project.
You've done great, so I love it
Thanks Nick!
Do you think that the difference made with these devices would make a difference in a racing situation? The VW reaches speeds up to 130 miles an hour.
Hi THEDnARACER,
At speeds of 130 mph aerodynamics are by far the most dominant source of resistance (easily over 80%).
The vortex generators can make a difference for sure, to reduce drag for example. But careful application is advised.
Also, they influence the air that is fed to any rear wing for example, if you have one!
Kind regards,
-The AirShaper Team
Fast moving air stuck to the window will create suction and the vortex generators create drag. This video misses the point completely: for you, reducing drag is more important than clean windows. A spoiler above the window to separate the airflow will increase the pressure on the rear window and actually push you forward - actually reducing drag
@@JeremyParsons Hi Jeremy, I've answered in part to this question in my other answer, see below. Looking forward to your comments.
very good
jazakallah ❤️
Vortex generators utilize the same effect that dimples on a golf-ball utilize, except on a golf ball we have to cover the entire ball because we don't know where the front and back is because the ball is spinning, whereas on a car or airplane we know where the front and back is so we only place them strategically.
Hi Erik, thanks for the comment, that is entirely correct! In theory, you could make a golf ball fly even further if it's orientation would be constant 🙂 for cars, this is almost true: sidewinds, upstream turbulence etc can alter their behavior and thus the impact in drag.
Seria legal fazer uma série de vídeos com melhorias possíveis na aerodinâmica do Volkswagen Beetle 👍🤝
That would indeed be a lot of fun to do! For sure, cleaning up the underfloor would make a huge difference.
@@AirShaper Daria uma belo de um conteúdo e marcaria a história de reais possíveis melhorias 🔝🔝🔝🚀🚀🚀🚀
@@isaacchiappetta4042 It would indeed! At the moment, we're aiming to spread our attention across various segments. If we ever revisit the beetle, then we can certainly do this :)
@@AirShaper olha o mundo é pequeno estou nesse momento no Brasil América do Sul mas sonhar não custa nada 🤣🤣🤣 , Grande Abraço !
Good video! The facts about functional VGs in general automotive applications has become so distorted amidst a decade of EVO wannabees. You don't need a wind tunnel to determine the point of separation, but you still need to "test"(w/tufts and/or powder) to determine an optimal mounting position.
Thanks Micro Air! Indeed, a number of cases where vortex generators were applied on iconic cars have triggered others to apply them as well, also on cars where they're less relevant. These days the back of cars is so gently inclined that VGs are usually not required, as there is little seperation before you reach the trunk.
well done
Thanks Afzal!
are useful on mazda mx-5 rf roof ?
Depends on the model, if the slope of the rear window is quitr 'negative' and separationnis expected then it might make sense. If it's upstream of an abrupt cut-off of the roof line (like the latest model) then the air will separate anyway and vortex generators make no sense. A cfd analyse of the base model will provide that insight!
@@AirShaper Thanks. I refer to the mx-5 ND (4th gen), in particular to the RF version (obviously when it is full closed )
@@bscgarage If I'm looking at the correct MX5, then it's the one with the abrupt end of the roofline: so you would have flow separation there anyway. So then vortex generators wouldn't help, in my opinion.
@@AirShaper Thank you very much! I would go for a little trunk spoiler!
How would these work on a pickup truck?
Hi Paul, a pickup truck typically has quite an abrupt drop after the front cabin. So there's not really much of a "negative curve" going on there, so I would guess vortex generators have less of an effect. But it would definately be worth the test :):)
Important note that without proper rear wing those vortex generators will do more harm than good.
Hi Eric,
indeed, it's possible that by pulling down the airflow you actually generate more drag. Another aspect is the "stability" of the flow pattern, which can also be influenced (in both a good or bad way) by influencing the separation location with vortex generators.
Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure so fast moving air stuck to the Beatle's rear window will create suction (increasing drag) and the vortex generators will also directly create drag. This video misses the point completely: the Beetle needs a spoiler above the rear window. If the angle of the rear window was flatter, then the spoiler could be lower like on a Porsche 911 but a Beetle needs separation above the rear window.
Hello Jeremy, just like the Bernoulli's principle is not enough to explain how wings work, it is not enough to explain the complex flow structure we're looking at here. Yes, a small spoiler creating a separation point could be a valid option to reduce drag, just like the coda tronca cars from the past. But it's not the only option: the vortex generators themselves indeed create extra drag locally. And yes, they speed up parts of the flow close to the window. But that is not the only aspect, they decrease the large wake zone at the rear of the car, which is creating a large suction effect as well. As you know, similar effects have been demonstrated to work on golf balls (the dimples). Hope you agree to this explanation, let me know your opinion.
Jeremy Parsons wrong. bernoulli's principle will create lift on the car, not drag. with increased flow attachment the car will have increased lift according to bernoulli's principle. this could be offset with a trunk spoiler which could be smaller because the increased attached flow increases the efficiency of the spoiler. the reduced low pressure wake behind the vehicle will reduce overall drag. be careful when applying physics there are often multiple effects to consider.
waste of money, its not essential at all just drive the car.
It's indeed not essential to drive the car. And on modern cars, there is no need at all because the base shape is streamlined enough to avoid separation without vortex generators. But for some applications (in sports, aviation and cars) it can be useful to optimize for efficiency, range, top speed, ...