Turbulators

[Sabarras]

Hello,
I'm new to the forum, I just discovered turbulators - thin zig-zag strips (or rows of dimples) strategically positioned to generate tiny vortices and maintain a more laminar flow at the rear side of a wing.

I was researching the aerodynamics of golf ball dimples that trip the air streams into microvortices on the lead surface in order to reduce the normally large wake round shapes generate.

A single turbulator strip is all that is neccessary on a smooth cylinder to achieve the same effect when the direction of the air flow is known.

My question is: If you have a cylinder (eg. a roll over hoop), at which angle do you think would be the best place to position a zig zag turbulator tape to get the maximum drag reduction? Imagine that the lead surface is 0° and the tail is 180°

Some info on turbulators:
https://www.youtube.com/watch?v=MUbh8uYNYC8
https://wingsandwheels.com/turbulator-dimple-tape.html

Lead edge turbulator strip on wing shape:

[jjn9128]

The efficacy of such devises really is dependant on Reynolds number. They also don't promote laminar flow - the clue is in the name... they promote a turbulent boundary layer which in regions with large adverse pressure gradients helps the flow to remain attached.

Generally the ideal position would require some experimentation to find, but it should go upstream of the natural boundary layer transition.

I'd say on the roll hoop of a race car you'd get a better drag saving with an aerofoil shaped fairing than trip strips.

[roon]

Halo fairing development should seem to back you up, jjn. Early on, some had vortex generators. Most have moved to thin flow conditioner/turning vanes in the form of long thin wing forms. All have some sort of teardrop, trailing edge taper.

[subcritical71]

sorry, i cant help bit think of this video when anyone mentions a turbolator....

[jjn9128]

sorry, i cant help bit think of this video when anyone mentions a turbolator....

[Zynerji]

sorry, i cant help bit think of this video when anyone mentions a turbolator....

https://youtu.be/rLDgQg6bq7o

... and I caught a ton of down votes when I posted this vid last year...

[subcritical71]

sorry, i cant help bit think of this video when anyone mentions a turbolator....

https://youtu.be/rLDgQg6bq7o

... and I caught a ton of down votes when I posted this vid last year...

That was one of the greatest inside jokes of all time. No pun intended -> Time Magazine actually went with it in the May 1946 issue! Even General Electric, Chrysler and Rockwell Automation got in on the joke later on.

[Sabarras]

The efficacy of such devises really is dependant on Reynolds number. They also don't promote laminar flow - the clue is in the name... they promote a turbulent boundary layer which in regions with large adverse pressure gradients helps the flow to remain attached.

Generally the ideal position would require some experimentation to find, but it should go upstream of the natural boundary layer transition.

I'd say on the roll hoop of a race car you'd get a better drag saving with an aerofoil shaped fairing than trip strips.

Yes, it would reduce the drag of massively if you changed the shape.
A lot of older race cars have round section tubing hitting the wind, suspension arms, wing struts etc. These cars still compete in historical races, it would be an interesting challenge to make a cylinder as aerodynamic as possible without changing its shape.

[Tommy Cookers]

the highest conventional drag coefficient is at low Re - where flow is attached
add-ons may do best if they can promote wake convergence not try to delay it

btw
golf balls spin and generate lift
and
the streamline section isn't so clever where AoA is significant - what use are 'aerodynamic' bicycle spokes in crosswind ?

[jagunx51]

https://www.racecar-engineering.com/art ... duce-drag/

[FW17]

[Stu]

the highest conventional drag coefficient is at low Re - where flow is attached
add-ons may do best if they can promote wake convergence not try to delay it

btw
golf balls spin and generate lift
and
the streamline section isn't so clever where AoA is significant - what use are 'aerodynamic' bicycle spokes in crosswind ?

If crosswinds are severe, ‘solid’ spoked wheels (or even deep section wheel rims) become an issue for cycling (the more extreme versions are used for Time-trialling only; UK rules stipulate a maximum front rim depth for any participant). Lighter riders have issues at lower cross wind speeds/yaw.
Most serious TTers have multiple wheelsets that suit differing conditions (the days when people would ride to and from events are over, with riders competing in ‘club-only’ events, turning up in cars with a selection of kit).

A picture of a Zipp disc wheel is shown above, these are only legal for rear wheel use in UK TTs (legal for track and UCI competition at the front), and have been the subject of a great deal of discussion (since they were launched, many years ago) as to the purpose of the dimples. Many riders fell for the marketing hype, however in-the-flesh a large proportion of the dimples are covered in the makers logo (which until fairly recently took the form of a sticker in fairly thick vinyl….

Bear in mind that TTers are particularly anal about drag reduction (even going to the extreme of testing chain lube in order to save 0.5W of drag).

[henry]

Bear in mind that TTers are particularly anal about drag reduction (even going to the extreme of testing chain lube in order to save 0.5W of drag).

And by the time they get to the track they’re chasing tiny gains.

Here’s the Olympic Danish 4K Pursuit team with medical tape on their shins potentially* to trip the boundary layer to keep it attached round their calves.



The authorities took a dim view and they didn’t use it in subsequent rounds.

They’re “only” doing about 70kph so not so relevant to F1.

*might have been to hide something else or psych out the opponents.

[Stu]

Bear in mind that TTers are particularly anal about drag reduction (even going to the extreme of testing chain lube in order to save 0.5W of drag).

And by the time they get to the track they’re chasing tiny gains.

Here’s the Olympic Danish 4K Pursuit team with medical tape on their shins potentially* to trip the boundary layer to keep it attached round their calves.

https://road.cc/sites/default/files/st ... i0wij.jpeg

The authorities took a dim view and they didn’t use it in subsequent rounds.

They’re “only” doing about 70kph so not so relevant to F1.

*might have been to hide something else or psych out the opponents.

I would imagine that the tape works to some degree. The UCI have a dimensional limit on the thickness of seams in clothing and material texturing. Trip-socks are a thing, they can actually measure the difference in a wind tunnel…
…so the UCI also have a limit on sock length!

And we think that the FIA are bad!!!