PVC Blades and the Venturi Effect

System
System Posts: 2,511 admin
in Wind Power Generation #1
Im new here and I had a question that has been bugging the very Devil out of me:

I am following the model of cutting come PVC pipe to create blades for a turbine and I was hoping the Aerodynamics folks could help me out:

If I drill holes through the lateral surface of the blade (parallel with the surface of the hub) it will allow the air to pass over the holes without passing though the holes. Will this create a Venturi Effect and make the blades more efficient?

Theory says that it will draw more air through the holes creating a little thrust or, at the very least, eliminate some of the drag.

Any Ideas?

Rob
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,664 admin
    #2
    Re: PVC Blades and the Venturi Effect

    That is probably a difficult question to answer with out doing the testing... First you have to determine if you have turbulent or laminar airflow... And if you have laminar airflow and lots of bugs in your area--the laminar flow can break down from the bugs building up on the leading edge. Lastly, the first 1/3rd or so of the airfoil surface tends to be more critical (orientation, smoothness, etc.) than the rest of the trailing surfaces. So, exactly where you place the holes will have an effect too.

    It is an interesting question--I am wondering if you would have more/better answers at the www.otherpower.com website (they also have a forum too)--They really focus on DIY wind turbines (we don't really talk nearly as much about them here).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BilljustBill
    BilljustBill Solar Expert Posts: 219 ✭✭✭
    #3
    Re: PVC Blades and the Venturi Effect
    paleosmithGA wrote: »
    Im new here and I had a question that has been bugging the very Devil out of me:

    I am following the model of cutting come PVC pipe to create blades for a turbine and I was hoping the Aerodynamics folks could help me out:

    If I drill holes through the lateral surface of the blade (parallel with the surface of the hub) it will allow the air to pass over the holes without passing though the holes. Will this create a Venturi Effect and make the blades more efficient?

    Theory says that it will draw more air through the holes creating a little thrust or, at the very least, eliminate some of the drag.

    Any Ideas?

    Rob

    I saw where they tried the holes in the surface of a full size test airplane in the 1970's.

    There were two problems: One: the holes were small and required regular cleaning. Two: they had to beefup the wing skin to allow for the structural difference a load bearing surface peppered with holes.

    The wing's strength came from the outer skins being far apart as they followed the wing ribs and main spar. On your PVC blades, drilling holes in thin material would weaken it and may provide a "Cut on Dotted Line" for the stress loading as the blade shatters...

    If you've ever seen the constant movement of watt meter of an operation grid tie wind generator, it really shows what appears/feels like a steady wind as an almost constant varing of the pressure on the turbine's blades.

    Sun and temps can really take their tole on exposed PVC pipe; think what your modified PVC blade has to endure when you add wind pressure and age to the mix.
    Bill
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