Vortex Generators

Discussion in 'Gen 4 Prius Technical Discussion' started by dstahre, Jun 14, 2016.

  1. dstahre

    dstahre Member

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    I'm familiar with vortex generators from aviation. They are typically used to ensure that the boundary layer of airflow does not separate from the aircraft surface. Does anyone have an explanation for the vortex generators on Gen 4 next to the side mirrors? I've also noticed a single generator on the side of either tail light. Anyone got a good explanation?
     
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Toyota wanted better MPG, and spent time in a wind tunnel to get it?
     
  3. fuzzy1

    fuzzy1 Senior Member

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    Didn't I read that vortex generators have also been used on some aircraft for noise reduction?
     
  4. Topp Cat

    Topp Cat Member

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    Vortex generator on Prius is generally use to divert air flow around the mirror mostly for wind noise the crease on the side of body is use to create a air flow channel reducing air turbulence/ low pressure Along the side of the car.
     
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  5. dstahre

    dstahre Member

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    No doubt, just wondered what issue they were addressing with them?
     
  6. Trollbait

    Trollbait It's a D&D thing

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    A vortex generator can also be used to promote clean separation of air flow from a surface. Air that just spills off the sides and roof of a car will cause drag inducing turbulence.

    edit: just noticed a word choice that meant the opposite of what I meant.
     
    #6 Trollbait, Jun 15, 2016
    Last edited: Jun 16, 2016
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  7. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    The ones on my v seem to be working on airflow around the outside mirrors. US law does not allow cameras instead of mirrors, but it would help airflow.
     
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  8. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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  9. bwilson4web

    bwilson4web i3 and Prime

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    A couple of years ago, I did some tuft testing with our 2003 Prius and found reverse flow behind the rear window:
    Documenting NHW11 Prius rear window flow separation; testing AirTab vortex generators - Page 2 - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

    [​IMG]

    So I tried some vortex generators and suppressed the reverse flow. But benchmarks did not show a measurable effect on MPG.

    My experience and the literature suggests there are 'edge conditions' where vortex generators can make a measurable difference. But it is by no means a 'magic wand.' You have to test and confirm the effect.

    Bob Wilson
     
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  10. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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    I like the challenge, but lack the ability to measure to the degree required to isolate the effect of the generators. I have done some lightweight research and cannot find any solid evidence of measurable delta to MPG. Comes down to aestics
     
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  11. Trollbait

    Trollbait It's a D&D thing

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    The one or two posters that have tried AirTabs on their trucks and boxy trailers may not have seen an measurable MPG improvement, but they were happy with the trailer's improved manners. A blog that did the same string test on a gen1 Prius and Insight also placed 4 just behind and underneath the Insight's front bumper claimed it improved the car's highway handling. The others actually worsened the cars drag by the string test. The ones by the Prius mirrors seem to be more about reducing noise than lowering drag in general.

    VG can serve purposes beyond lowering drag.
     
  12. sdtundra

    sdtundra Senior Member

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    Toyota seems to have some type of vortex generators on the majority of their cars and trucks. Looked at a 2015 Tundra and the tail lights had 2 as well as in the gap between the mirror and a-pillar.
     
  13. dstahre

    dstahre Member

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    Reminds me of an experiment I did with my El Camino 30 years ago, I tufted the bed and noted that from about the wheel wells forward the air flow was toward the cab and from the wells back it was toward the rear. I'm sure there is some impact from them that may be buried in the "noise level" but perhaps the combined effect of all of them does make a difference. BTW: I've noticed that the shape of the so-called "shark" antenna is very similar to the vortex generator shape and perhaps was intended to also serve that function?
     
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  14. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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    I work at an aerospace company and we have a few engineers who told me that this could help, and could not do any harm. So I thought I would give it a go. I like the look.
    image.jpeg image.jpeg
     
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  15. bwilson4web

    bwilson4web i3 and Prime

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    Oh not against VGs but their use needs to carefully tested.
    Did you do an A-B-A test?
    • A - baseline the car without the change
    • B - repeat baseline with the change
    • A - repeat baseline without the change
    This ensures the change has an effect and quantifies it. In my case, I used a 2003 Prius and found no measurable effect that exceeded the accuracy of the benchmarks. I could see it reduced the reverse flow behind the rear window but not enough to show up in the MPG.

    Still, if it looks good, I understand 'bling' ... been married for too many years to express any esthetic beyond,"Looking good babe."

    Bob Wilson
     
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  16. dstahre

    dstahre Member

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    I agree, though keeping the boundary layer attached should improve drag!
     
  17. bwilson4web

    bwilson4web i3 and Prime

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    There are other techniques. I'd thought about a vacuum pump taking air from the front gap between the roof and hatch. But I suspect the 'low hanging fruit' are wheel well covers both front and rear. For now, moon-caps but what I've seen on the market, I would not touch.

    Bob Wilson
     
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  18. Tideland Prius

    Tideland Prius Moderator of the North
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    The aerodynamic fins underneath the rear of the car are there to ensure a smooth exit of underbody airflow at the rear of the car.

    The vortex generators that you speak of near the mirrors are for stability. I really wished I saved a local copy of an article I read somewhere on a Lexus enthusiast site that explained the generators and the engineers' thought process. From what I remember, it enhanced stability by creating controlled vortices down the side of the car (hence the name vortex generator). This means the air that is tumbling down the sides of the car are the same on both sides of the car, reducing buffeting caused by uneven pressures on each side of the car because of different sized vortices (without the vortex generator).

    Edit: I also found information that describes what you mentioned earlier about drawing the flow closer to the body (so rather than preventing separate of airflow from the surface, it's just drawing it in tighter to the body)
    Factory / OEM vortex generators on trailing edge (side) of Toyota "Prius C / Aqua" - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com
     
    #18 Tideland Prius, Jun 19, 2016
    Last edited: Jun 19, 2016
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  19. Frederickdawg

    Frederickdawg Active Member

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  20. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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    No extra noise even with the moonroof open.
     
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