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Thread: Fluid dynamics

  1. #1 Fluid dynamics 
    Forum Sophomore biohazard87's Avatar
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    So, I've been asking around but still have now answer. I've looked on line for over two weeks, to no aviel, and I'm running out of time. Does anyone know how to measure laminar flow? If there is a dufferent way to measure laminar flow in a gas than in a fluid I need the way for a gas. Please help me. My teachers, emphasses on the plur, don't know any thing to help me. One teacher is a physicst teacher and the other is an earth science teacher, but they have no idea what to do with laminar flow.


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  3. #2  
    Universal Mind John Galt's Avatar
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    Which aspect of laminar flow are you seeking to measure? Velocity? The occurence of laminar versus plug or turbulent flow? Flow rate? At the moment your question is of the general type 'How do I measure oranges?' and consequently not very clear, at least to me.

    I can calculate whether or not you have laminar, turbulent or transitional flow for oil well drilling fluids, but I doubt if that would be of much help to you.

    So what are you actually wanting to measure?


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  4. #3  
    Forum Sophomore biohazard87's Avatar
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    Oh, well, I'm not sure exactly what part I need to measure. I am trying to see why a spining card will fly further than a non spining card. I figure it is because the lamina layer forms more easily, but also because the spining creates lift. Maybe you could help me narrow this down. None of my teachers could help me and I still can't find anything on the internet to help me narrow down what I need to measure.
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  5. #4  
    Universal Mind John Galt's Avatar
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    This is off the top of my head, so I don't know where it is going, if anywhere.

    First, have you confirmed experimentally that a spinning card will travel further than a non-spinning card?
    If the answer is yes, have you done this
    a) for a variety of circumstances, and
    b) multiple occasions for each circumstance

    Now, your hypothesis is that this is because the laminar layer forms more quickly with the spinning card. Why do you think this?
    What other explanations have you considered? Why did you reject them?

    This hypothesis does not seem a very likely one to me, but that is based on gut feel and not evidence.

    What you are trying to measure then is the rate of transition to laminar flow. I can't see anyway of doing that without a wind tunnel, smoke generator and high speed photography. That does not mean there isn't a way, just that I'm not bright enough to think of it in a couple of minutes.

    This isn't helping you very much. Could you not explore some of the other possible explanations for the greater distance?

    Come back on these points and we can try to talk some more. Which time zone are you on?
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  6. #5  
    Forum Cosmic Wizard SkinWalker's Avatar
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    I should think it would have to do with the amount of energy that can be applied to the card to begin its motion. If you apply the same amount of energy to a card (playing card?) that will make it spin as it travels to a card with the intention of *not* spinning it, you have to find a way to apply the force uniformly to the card.

    By *spinning* the card, the kinetic energy is transferred to it and distributed more evenly, keeping the card from warping in flight. If the card is put into motion without spinning, it will bow due to air resistance.

    But that's just my slightly under-educated guess (very little physics experience).
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  7. #6  
    Forum Sophomore biohazard87's Avatar
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    Okay, I have confirmed that the spining cards travel farthur than the non spinning playing cards.

    My Hypothesis is actually that the spining cards will form the lamina more Easily not more quickly, because as far as I can tell the non-spining cards formed no lamina. I also considerd the fact that the spinning cards created lift from the spin but I believe that the lift generated is not sufficent force to lift the card that far. The only other possiblity considered was the fact that by spinning the card forward momentum was increased as the card would be launching its self forward, but this was eleminated as the cards would also be launching themselfs backward as well.

    I do have a wind tunnel, I can get a smoke machine very easily, but I lack a high speed camera.

    Oh and I am on New York time. Not sure what the time zone is called other than the Eastern time zone.
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  8. #7  
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    The fact that the card is spinning (about an axis, presumably through its centre of mass) keeps the card stable within a plane (perpendicular to the spin axis). The added stability prevents the card from "flailing about", thus stabilising velocity and allowing the card to travel further.
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