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When is turbulence beneficial?

  1. Sep 29, 2008 #1
    Hi guys.
    I know turbulence is a b($#H when trying to explain and often poses problems in flyid dynamics.

    However, our university lecturuer has thrown this at us to think about as it's a pretty interesting topic and I thought there might be some people out there that have ideas about it.

    The cases he has mentioned include:
    1) around a golf ball (separation promotion resulting in speed)
    2) leading edge extensions (suppress stall on aircraft)

    But he has bonus marks for the person to come up with the best case. ;)

    I'm thinking biology at lower scales like life science. Possibly turbulence was useful for evolution or growth ect. like plant pollenisation. It's a pretty specialised topic but if any of you guys have some ideas would be cool to hear your thoughts.

    P.S. I know it comes under HW but thought it might be a cool topic and something I myself find interesting anyway.
  2. jcsd
  3. Sep 29, 2008 #2


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    It would be very difficult to mix things without it
  4. Sep 29, 2008 #3


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    A good friend of mine has won the national championship in his drag-racing class a couple of times. He claims that by polishing intake manifolds to enhance laminar flow you create drag on the incoming air-fuel mix. He has the interior surfaces of his intake manifolds machined so they are just slightly rough, and claims that the layer of micro-turbulence created by the air-fuel mix as it contacts the surface acts like little bearings, allowing the bulk of the air-fuel mix to get to the cylinders with as little drag as possible. Just a thought. Not a winning idea, certainly, but the fact that he was into this stuff over 20 years ago impressed the hell out of me. He was a HS graduate and a Vietnam Vet, and was working as a laborer in a pulp mill, and he taught me stuff about the physics of IC engines.
  5. Sep 29, 2008 #4
    I can think of a lot of applications. Such as turbulence generators on aircraft wings or structures. Or what was mentioned before, the combustion chamber of an ICE. Engine makers purposely create turbulence inside the combustion chamber to increase efficiency.
  6. Sep 29, 2008 #5
    Heat transfer coefficient, such as in a heat exchanger tube, is improved as the Reynolds number rises (ie, turbulence helps).
  7. Sep 29, 2008 #6


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    I suspect your prof wants you to stay within the realm of fluids.
  8. Sep 29, 2008 #7
    Wow yeah i never thought of the heat transfer idea. I think that might be a winner with many applications to that.

    Yeah fair enough. Trying to think a little too much.
  9. Sep 29, 2008 #8


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    Small radio control gliders use turbulator strips to trip up the air flow from laminar to turbulent to control when the streamline nearest the wing transitions from laminar to turbulent, because the turbulent air flow ends up staying "attached", providing a better lift to drag ratio. For full scale glider, the surfaces are roughed up with find grit sandpaper or with strips to do the same thing. Do a web search for "oil flow test glider" for examples like this one:

  10. Sep 29, 2008 #9
    mgb gave you the clues you need. Don't forget water is a fluid. The sun is made of turbulent--stuff... the upper atmosphere of Jupiter has great laminar streams
  11. Sep 30, 2008 #10
    Yeah i think i know what the representation of non turbulent is. Kind of like mixing paint and it takes ages for the things to mix.

    Anyone know if it would just be a time thing (like mixing would just take longer) or would certain things not mix 'at all' ect.?

    You don't need eddie structures to mix two fluids right? Diffusion will do the rest when they arn't present?
  12. Sep 30, 2008 #11

    Andy Resnick

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    Diffusion will act to mix two fluids, it's just a very slow process (but fast enough for microfluidic technologies).

    Turbulence means a lot of things, one of which is that particles no longer follow streamlines; this is why the presence of turbulence increases the mixing rate. That's true for miscible and immiscible fluids; for chemically inert and chemically reacting species.
  13. Sep 30, 2008 #12
    Mortgage and financial crisis in USA is the best example of turbulence. Laminar flow has stopped, everybody can't think in unisone. Government tries to control Reinold's number to get richest people to be more rich, but elections spoil the result.

    To what extent is any given man morally responsible for any given act? We do not know.
  14. Sep 30, 2008 #13
    Without turbulence the average wind speed would cut you to ribbons. The only living things left outside the oceans would be microorganisms living outside the sand blast.
    Last edited: Sep 30, 2008
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