Vortex generators (1 Viewer)

[Two on Tour]

Does anybody have vortex generators fitted on their van/motorhome or has anybody had any experience using them on a van/motorhome ?

I have experience of vortex generators when I worked for a hanglider manufacturer many years ago and we developed and produced a hanglider that used vortex generators to improve airflow over the wing, so I know they work and having viewed many youtube video's of trucks and US RV's using them I have ordered some up to give them a try.

Here a bit of information to get the conversation going.

 

[andy63]

Interesting... ive no doubt the science behind them is correct but im wondering if they can be fitted as a diy aid and be effective without correct positioning etc... which could only come from access to wind tunnel testing of a model example..
And most motorhomes have such an array of gadgets fitted to their external surfaces i doubt they could be fitted effectively...
Thats my initial thoughts.
Andy.

 

[Two on Tour]

Interesting... ive no doubt the science behind them is correct but im wondering if they can be fitted as a diy aid and be effective without correct positioning etc... which could only come from access to wind tunnel testing of a model example..
And most motorhomes have such an array of gadgets fitted to their external surfaces i doubt they could be fitted effectively...
Thats my initial thoughts.
Andy.

My main aim in fitting them is to try and clean up the airflow as the air leave the back of the van, the theory being that the vortices leaving the generators have a fast and strong stable spin that offers stability which is less affected by cross winds and passing trucks.

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[andy63]

My main aim in fitting them is to try and clean up the airflow as the air leave the back of the van, the theory being that the vortices leaving the generators have a fast and strong stable spin that offers stability which is less affected by cross winds and passing trucks.

Got that... but the airflow along most motorhomes isnt likely to be straight fwd as with your average truck or van , with awnings, pannels, aeriels , sat dishes or domes , or whatever some folk carry on their roof.. so how predictable does the air stream have to be for the vortex units to be effective and where best to place them,
Heres a picture of my roof... cant see much helping that in terms of aerodynamics

stability which is less affected by cross winds and passing trucks.

If thats an issue stability in cross winds etc can be helped a lot by fitting air assist...which i suspect would have a more certain effect than the vortex generators...
Andy.

 

[Jands]

Snake oil.
As a licenced aircraft engineer know what vortex generators do.
Re-energise the boundary layer on the surface to prevent stiction of air which increases drag. This is at high airflow speed. Aircraft also use winglets to reduce more parasitic drag as the airflow leaves the end of the wing.
All these are calculated using wind tunnels and computer models to see if there is any benefit as something sticking out in the airflow will increase drag.
We are driving something which resembles a motorised brick at low speeds.
A flat back is a awful aerodynamic shape but a taper shape is impractical.
With a flat back the airflow will circulate round the back causing drag, little blades stuck on the end of a motorhome will do nothing to stop this, they will only increase drag.
If they worked they would be on mass produced cars as they like to promote technology that reduces fuel costs. I suspect they have an adverse effect on vehicles aimed at doing a max of 70 mph.

 

[Two on Tour]

Got that... but the airflow along most motorhomes isnt likely to be straight fwd as with your average truck or van , with awnings, pannels, aeriels , sat dishes or domes , or whatever some folk carry on their roof.. so how predictable does the air stream have to be for the vortex units to be effective and where best to place them,
Heres a picture of my roof... cant see much helping that in terms of aerodynamics
View attachment 256236



If thats an issue stability in cross winds etc can be helped a lot by fitting air assist...which i suspect would have a more certain effect than the vortex generators...
Andy.

Yes, my roof has pretty much the same clutter less the kayak.

My thinking is that the turbulent air generated by the guff on the roof and sides of the van/motorhome would normally just pass of the back of the van/motorhome as unstable and haphazard leaving it susceptible to the crosswinds pushing it about and in turn the van/motorhome.
If the vortex generators are placed at the rear edges of the van/motorhome then this unstable and haphazard air flow could be straighten and speeded up as it leaves the back of the van/motorhome and this stabilised air flow should offer better stability along with air assist suspension.

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[The Wino]

Snake oil.
As a licenced aircraft engineer know what vortex generators do.
Re-energise the boundary layer on the surface to prevent stiction of air which increases drag. This is at high airflow speed. Aircraft also use winglets to reduce more parasitic drag as the airflow leaves the end of the wing.
All these are calculated using wind tunnels and computer models to see if there is any benefit as something sticking out in the airflow will increase drag.
We are driving something which resembles a motorised brick at low speeds.
A flat back is a awful aerodynamic shape but a taper shape is impractical.
With a flat back the airflow will circulate round the back causing drag, little blades stuck on the end of a motorhome will do nothing to stop this, they will only increase drag.
If they worked they would be on mass produced cars as they like to promote technology that reduces fuel costs. I suspect they have an adverse effect on vehicles aimed at doing a max of 70 mph.

Snake oil sometimes but I remember gliders in the 1980's being well ahead of commercial aircraft in adopting winglets (to stop spanwise flow) and turbulator tape to detach the flow in front of the alerons they were also very early to have laminar flow wing sections the hobbyists sometimes come up with good stuff (although to be fair a lot are probably gliding for a hobby when their work is in aircraft design!!!!)

 

[Two on Tour]

Snake oil.
As a licenced aircraft engineer know what vortex generators do.
Re-energise the boundary layer on the surface to prevent stiction of air which increases drag. This is at high airflow speed. Aircraft also use winglets to reduce more parasitic drag as the airflow leaves the end of the wing.
All these are calculated using wind tunnels and computer models to see if there is any benefit as something sticking out in the airflow will increase drag.
We are driving something which resembles a motorised brick at low speeds.
A flat back is a awful aerodynamic shape but a taper shape is impractical.
With a flat back the airflow will circulate round the back causing drag, little blades stuck on the end of a motorhome will do nothing to stop this, they will only increase drag.
If they worked they would be on mass produced cars as they like to promote technology that reduces fuel costs. I suspect they have an adverse effect on vehicles aimed at doing a max of 70 mph.

Quite a few car manufactures do such as Toyota and Subaru, see video above.

NASA's own wind tunnel testing showed that vortex generators worked from about 40 kph up.


So why did "Kamm tail" work on race cars then ?

https://en.wikipedia.org/wiki/Kammback

 

[Two on Tour]

Snake oil.

If they are snake oil then some of these users are pretty big players that have been duped.

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[chesterfield hooligan]

I would assume on lorry cabs it is a attempt to get the air flow strightened to jump the gap between the cab and trailer, to try to reduce the turbulence behind the cab thus reducing drag. Or could be just snake oil.

 

[Geo]

I maybe tempted tp try them out but when and only when
they appear in packs of 12 at the £ Shop or Wikos
Because if it dont appear in those two outlets its a looser
If it really worked the Master of Vortex, Mr Dyson would have had them out at £300 each

 

[Jands]

Must admit never noticed them on vans and lorries, although never looked.
Will have to look now to see if I can see them fitted.
Aircraft vortex generators are nothing more than a bonded on L shaped bracket slightly angled on the leading edge, fitted at a slight angle to the airflow.
Know the theory but not sure of the advantage, especially to something as aerodynamic as a motorised brick.
Am interested if the shape of an A class is aerobynamically worked out or just what looks good? Mind you Shorts designed something that looked like a flying box.

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[hilldweller]

If they are snake oil then some of these users are pretty big players that have been duped.

"The King's New Clothes".

 

[Two on Tour]

Airtab and Ecofins are in the main the one that look to be fitted by most lorry operators using vortex generators. Both are American companies but Airtab have a UK dealer.
I have had quite a long chat with the Airtab UK dealer who is obviously out to sell the produce but was not doing a hard sell and by all accounts there are out there in the UK motorhomes using the Airtabs
Measuring up our motorhome, I need about 50 of the vortex generators to cover the two sides and roof and if I were to use Airtabs then that would set me back about £250.
I'm game to try them out as they are on a self adhesive foam and stuck on and can be removed if required, but the 250 quid for a might work was too much for me to swallow so I have ordered 50 Chinese ones from China for a little under £65 plus what ever I get hammered for with import duty and VAT.

Having had a little scout around the internet this evening I have come across a couple of paper written by credible authorities that being NASA and the Australia New South Wales government department. I know these papers relate to trucks but they are still for me encouraging reading as I want to be convinced of their usability in a motorhome environment.

https://spinoff.nasa.gov/Spinoff2008/t_3.html

http://www.rms.nsw.gov.au/documents...r/case-study-aerodynamic-vortex-generator.pdf

 

[DBK]

So why did "Kamm tail" work on race cars then ?

https://en.wikipedia.org/wiki/Kammback

Not sure about these vortex things, they are a new one to me but might work in the same way a dimpled golf ball flies further than a smooth one - the turbulent boundary layer sticking to the surface of the ball longer and thus reducing drag.

But a Kamm tail is an easy one. The ideal shape for a vehicle at typical ground vehicle speeds is a tear drop. However, a long tapering tail isn't practical, as already mentioned. So the Kamm tail starts off with the shape of a long tail then chops it off at a sensible length. The result has a lower drag than a tail coming to a point in the same overall length. From memory the Marcos car of the 70s had a Kamm type tail.

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[funflair]

Well I’m on the A1 M1 and M18 today and not seen any yet, and I have been looking.

Martin

 

[jezport]

We had a Vortex exhaust system fitted to our last van. But bare in mind as well as having the vortex it was also a seamless tig welded system.
The initial first acceleration was better, the power on hills in 5th gear was better. Plus fuel economy was improved by up to 11%

This is not hearsay, it is my first hand experience.

 

[Two on Tour]

Vortex exhaust system

Just had a look at their website (https://vortexexhaust.com) if that's the same people.
May I ask what base vehicle was your last van and what did the system cost.

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[JJ]

Being a FLT I will save money...

Instead if paying money for vortex generators I will fasten my Honda EU 1000i onto my Hymer using cable ties...


JJ

 

[jezport]

Just had a look at their website (https://vortexexhaust.com) if that's the same people.
May I ask what base vehicle was your last van and what did the system cost.

Yes that's them. 2.8JTD Ducato, I had a full system including 2 high performance silencers. Cost around £1100.

 

[TheBig1]

as a cheap way to prototype and test, you could 3d print some and attach using trim tape

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[Two on Tour]

as a cheap way to prototype and test, you could 3d print some and attach using trim tape

I know 3D printers are coming in price but I don't think I'll pick one up for less than the 65 quid or so that the vortex generators I have coming from China cost

 

[TheBig1]

I know 3D printers are coming in price but I don't think I'll pick one up for less than the 65 quid or so that the vortex generators I have coming from China cost

but you don't buy a printer for just one job and the plastic to make the project is much cheaper than buying from china

 

[Jands]

We had a Vortex exhaust system fitted to our last van. But bare in mind as well as having the vortex it was also a seamless tig welded system.
The initial first acceleration was better, the power on hills in 5th gear was better. Plus fuel economy was improved by up to 11

Not disputing this you are saying it improved torque noticeably and also fuel economy.
If it worked that well as a selling point surely manufacturers would fit them as standard as torque/power and economy are the big selling points for all vehicles.
Would of been better than fixing the chip to give similar results on testing.
All vortex generators do is cause the gasflow/airflow into a swirling motion( vortex).
Can see how it could help exhaust gasses to move more freely but you do need some back pressure to maintain internal cylinder pressure.
Allowing exhaust gas to escape too freely would cause a vacuum in the cylinder, more fuel flow and less compression.
As I said if it was that good manufactures would fit them as standard.

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[jezport]

Not disputing this you are saying it improved torque noticeably and also fuel economy.
If it worked that well as a selling point surely manufacturers would fit them as standard as torque/power and economy are the big selling points for all vehicles.
Would of been better than fixing the chip to give similar results on testing.

Ran my van for years with it fitted, can't say more than that

 

[Two on Tour]

As I said if it was that good manufactures would fit them as standard.

Cost is why car manufacturers do not fit them, some years ago while at a Honda new model launch I asked a Honda technician why the new model did not have a low oil light on the dash, you guest it, it was a cost saving.

 

[Jands]

Few bumps/vanes sticking out would not be prohibitively expensive.
If they worked that well saving fuel would increase sales.
I am sure designers have looked at them and made their decision on effectiveness

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[Two on Tour]

Few bumps/vanes sticking out would not be prohibitively expensive.
If they worked that well saving fuel would increase sales.
I am sure designers have looked at them and made their decision on effectiveness

Do take it that you have not viewed this video then from earlier in this post ?

 

[tonyidle]

you do need some back pressure to maintain internal cylinder pressure.
Allowing exhaust gas to escape too freely would cause a vacuum in the cylinder, more fuel flow and less compression

There is never a case for back pressure in any exhaust. The moving slug of exhaust gas can be used to draw air through the engine during valve overlap. As the exhaust valve closes the air continues to flow into the cylinder via the intake tract until the inlet valve closes thus improving spent gas purging and cylinder filling. An exhaust correctly designed can also provide a pulse of positive pressure just before the exhaust valve closes. This is not back-pressure.

 

[Two on Tour]

Look what's arrive from China today, not bad, ten days from ordering to being delivered plus no VAT or import duty.

When the wind dies down a bit I'll paint them white and start by fitting a row along the top of the roof.
Before I put them on I'll tape some lengths of wool to the back of the van towards the top, go for a drive and film them before and after fitting the VG's to see if they really have any affect.
If they look to be beneficial then I'll put them down the sides as well.

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