Could these fins add a few precious miles to the range?

[zorzal]

http://www.independent.com/news/2012/apr/17/gas-pods-save-money-maybe-planet/#commenttoggle" onclick="window.open(this.href);return false;

The fins described int he article are in use widely, and the physics behind the description make a lot of sense: air can drag but it can also push.

The article says that the Leaf already sues some of the principles behind the fins (I imagine that's where the strange bulby light fixtures come from), I wander if more could be done.

Any experts in fluid dynamics who may want to comment?

Cheers

 

[pksd1]

Very interesting.

 

[lpickup]

Sounds pretty outrageous to me, and the claim that he used a "quarter tank of gas less", yet the study only showed a 5 percent boost? Red flag right there.

Having said that, there are "fin-like" protrusions on the underside of the rear of the LEAF. So who knows!

My understanding of the reason for the bulbous headlights is to direct the wind flow off the side view mirrors. Because the car is so silent, air hitting the side mirrors was a major source of cabin noise, so they designed the headlights to direct the air away from them.

 

[rawhog]

Look at the "fins" below the windshield.

 

[DTB]

Classic case of, "if its too good to be true...". Fins are already out there, I think some of the Evos have them. If they made any difference, Nissan would have paid the few cents and included them.

 

[TomT]

"Fins" like this are very common on aircraft and they do work. I question the 5 percent increase though as it is typically more like 2 or 3 percent in aviation applications...

 

[TRONZ]

Alot of aerodynamic compromise are accepted to make a vehicles form attractive and functional as a mass market product. Turbulators or trip strips are extremely inexpensive ways of mitigating these compromises. Each of these turbulators creates a vortex that energizes the boundary layer behind it. If an improvement is had then it indicates that airflow was seperating from the vehicles surface behind this region and causing drag. Turbulated air is far better than seperated air as the vortexes break the grip of suction that is apparently occurring. In the pecking order of Aero, Laminar flow is best but almost impossible to achieve at all speeds and localized flow angles. An optimized laminar flow can also be very dangerous for cars as any disruption at high speeds can cause a spontaneous Airshow when one is not wanted.

A simple inexpensive trick is to just go to the hardware store and buy a roll of sponge gap seal tape. Just tape temporary trip strips perpendicular to the airflow region you are trying to manage. If you notice an improvement then try moving the trip strip forward and backward from the separation bubble till its optimized for your commute. Then buy the turbulators once you've mapped out the surface for your car to match your aero needs.

Just to be clear though, the theory is very sound but difficult to measure since there is so many other variables in play each day. Good geek fun though!

 

[adric22]

I just rub snake oil all over my car. That increases the range by 300%.

 

[Nubo]

...A simple inexpensive trick is to just go to the hardware store and buy a roll of sponge gap seal tape. Just tape temporary trip strips perpendicular to the airflow region you are trying to manage. If you notice an improvement then try moving the trip strip forward and backward from the separation bubble till its optimized for your commute. Then buy the turbulators once you've mapped out the surface for your car to match your aero needs. ...

So what's a practical way to "notice an improvement" without a wind tunnel? Tape streamers to the car and observe from a chase vehicle?

 

[Danal]

I have these http://www.airtab.com/gallery/rv.html" onclick="window.open(this.href);return false; around the tail end of a very squared off "Toy Hauler" Class C RV. I can't tell the difference in gas mileage... too many variables... but the DEFINITELY reduced "tail wag" and also made a huge difference in the amount of dirt/rain/snow that collects on the back of the ramp/hatch.

Don't know where I'd put them on a Leaf. Need a wind tunnel...

 

[TNleaf]

I just rub snake oil all over my car. That increases the range by 300%.

:lol:

 

[TRONZ]

...A simple inexpensive trick is to just go to the hardware store and buy a roll of sponge gap seal tape. Just tape temporary trip strips perpendicular to the airflow region you are trying to manage. If you notice an improvement then try moving the trip strip forward and backward from the separation bubble till its optimized for your commute. Then buy the turbulators once you've mapped out the surface for your car to match your aero needs. ...

So what's a practical way to "notice an improvement" without a wind tunnel? Tape streamers to the car and observe from a chase vehicle?

Actually that is exactly what people do!

http://www.gassavers.org/showthread.php?t=1373" onclick="window.open(this.href);return false;

It's called Tuft Testing and Aero types get pretty geeked up over it. Google "tuft test" for images and feast your eyes. For a crowd of people that stalk Nissan ships I am a little surprised no one here has tuft tested a LEAF yet. Generally I would test for range over a control distance. The improvement is small so shows up best over a long distance.

 

[DaveEV]

Based on my research on vortex generators, the effect will be minimal at best and if placed in the incorrect location, will increase drag instead of decrease it.

You are probably better off getting some inexpensive steal wheels along with some "moon eyes" hub caps which definitely reduce drag.

 

[TRONZ]

Based on my research on vortex generators, the effect will be minimal at best and if placed in the incorrect location, will increase drag instead of decrease it.

Ya, these kinds of surface mods are usually only needed when a major aero mistake has been made or the vehicle needs to be used outside of the performance envelope it was designed for. Nissan has done their aero homework on the LEAF and I doubt many surface mods would yield practical benefits. If I were to "aero" a leaf I would drop it a couple of inches, fill in the rear wheel opening and moon eye the front wheels. Also throw on a set of ultralight 15's with narrow LLR tires and this would give a noticeable result for freeway warriors.

Just going to lightweight 16's is giving some people a 5% boost.

 

[TomT]

I have a hard time believing that to actually be true. The physics simply don't support it.

Just going to lightweight 16's is giving some people a 5% boost.

 

[EVDRIVER]

Dimples. Just get a bat.

 

[Smidge204]

Dimples. Just get a bat.

Speed holes!

=Smidge=

 

[Deleted member 770]

I have them on my ICE (Mitsubishi Evolution IX MR) - they're stock on Evo MRs. Mitsu calls them "vortex generators". They're claimed to help reduce turbulence in the airflow coming off of the passenger compartment. Do they do anything useful? I doubt it. Certainly doesn't seem to help my mileage at all.

 

[Nubo]

I have these http://www.airtab.com/gallery/rv.html" onclick="window.open(this.href);return false; around the tail end of a very squared off "Toy Hauler" Class C RV. I can't tell the difference in gas mileage... too many variables... but the DEFINITELY reduced "tail wag" and also made a huge difference in the amount of dirt/rain/snow that collects on the back of the ramp/hatch.

Don't know where I'd put them on a Leaf. Need a wind tunnel...

Well, the tail of the LEAF does get filthy quickly in wet conditions....

 

[Nubo]

...
It's called Tuft Testing and Aero types get pretty geeked up over it. Google "tuft test" for images and feast your eyes. For a crowd of people that stalk Nissan ships I am a little surprised no one here has tuft tested a LEAF yet. Generally I would test for range over a control distance. The improvement is small so shows up best over a long distance.

Thanks for the term. Knowing the jargon makes for much better searching! Sounds like something fun to try.