Factory / OEM vortex generators on trailing edge (side) of Toyota "Prius C / Aqua"
 

I just saw a review of the new Prius C hybrid in which it was stated that Toyota put vortex generators on the rear (side) of the car:

Source: http://youtu.be/JH5CCN3FwLs (at about the 3:25 mark)

http://ecomodder.com/forum/attachmen...1&d=1330962637

http://ecomodder.com/forum/attachmen...1&d=1330962586


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I can't comment on the credibility of what they reviewers say. It's just 2 guys reviewing a car. I presume they're repeating what a Toyota rep told them in the press briefing.

I tried to find a Toyota press release talking about this... and failed. (Maybe someone with better / more persistent digital ferreting skills can find something.)

It'd be good to have some official word on these things to help us noodle about their purpose/utility.

I figure this is somewhat significant because as far as I know, we haven't yet seen any credible evidence about the ability of VG's to directly affect the trailing wake of a vehicle in a way that's meant to improve efficiency.

(Versus ideas about stability or dust control on the rear glass as other claims that are sometimes made for placing VG's on the trailing edge.).

Given the location, probably to specifically address turbulence from the side mirrors.

I'm not aware of any type of VG that "cleans up" turbulence. (Meaning: if you place them in a turbulent flow, the results will be less downstream turbulence.)

Those don't look angled in the flow like VG's would be.

They look a bit like marketing and engineering had compromised on something that was intended to stabilize the flow.

jacob - I wondered the same thing (about flow direction). But from the wind tunnel & tuft tests I've seen, local flow isn't always going quite in the direction we would expect!

So I'm waiting to see what Toyota says about these things.

... with very strong input from marketing.

The angle may be getting almost close to VG, because the flow there is downward, (i.e., roughly parallel to the roof line) so their angle of attack might be 5-10 degrees.

Mercedes used to advertise their tailights that cleaned themselves aerodynamically. But then they dropped the design with the next styling change. Hmmm. "We were only kidding... made a great story though, didn't it?"

I have "vortex generators" on the top of my proof concept prototype -- they look like little wings. They are actually the supports for the canopy when it is flipped open. They are streamlined mainly for fun, and as a conversation starter.

The other issue is that vortex generators are intended to energize flow over the surface of a vehicle (typically one that flies). Putting them at the very back of a vehicle makes no sense at all. The energy you have put into creating these supposed vorticies would be entirely lost.

Fins on late 50's cars had no real function at all, as proven by their elimination in the early 60's. But the manufacturer's (especially Chrysler) advertised them as stabilizing devices, rather than as the space-age-looking styling gimmicks that they were. They were positively huge as compared to these tiny bumps on the Prius taillights.

(Chevy: 1956: rounded fin sprouting; 1957: real fin; 58: no fin at all. 59: fin flopped over on it side; 60: flopped over fin with a corner. 61 fins gone for good, never to return.)

Using my "better / more persistent digital ferreting skills", I found this from a Toyota Media Preview.

From Scribd: 12Prius c Technical Presentation v3 2

2012 Toyota Prius c
Media Preview
La Jolla ● January 2012

Page 18, Slide 41:

3. Aerodynamic features

a. Aero stabilizing fins are installed on the side face of the rear combination lamp and at the base of the outer mirror

1) Initiates aero vortices that accelerate airflow along body side
2) Reduces weak boundary layer airflow near body and draws the main airflow closer to the body
3) Increases vehicle stability
4) Effective over 25 mph

b. Under body covers improve airflow

1) Smooth under body airflow
2) Vortex generators accelerate airflow

c. Lightweight aluminum wheels and wheel covers are designed with aerodynamic performance in mind

d. 0.28 Coefficient of drag

moorecomp, you da ferret!

I'm not sure they're claiming any drag reduction with those side VG's... "Increases vehicle stability" seems to be the claim. (That happens to be a common testimonial of AirTab users.)

Point b2 sounds like they've got VG's underneath the car as well.

Still skeptical.

a Cd of 0.28 is impressive for such a short car, provided that such figure is real.

You can watch the entire presentation here.

http://www.youtube.com/watch?v=zTa8Dus1JMs