Foil series selection

Discussion in 'Hydrodynamics and Aerodynamics' started by anuprdk, May 9, 2018.

  1. anuprdk
    Joined: May 2018
    Posts: 9
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    Location: india

    anuprdk Junior Member

    hi,
    I am designing a fully submerged hydrofoil catamaran in canard configuration (one fwd, one aft) for a planing hull. I am forced to adopt a foil suited for turbulent working condition(Re > 5 e5). What series of foils should I use?

    take off speed 12 km/h
    max speed 36 km/h ; will reduce it if foil loading falls in cavitation bucket
    hull length 3 m
    foil span max 0.8 m as inverted T
    load on single foil 2700 N
    foil loading preferably 67000 N/ sq meter which gives a chord> 0.05 m

    If a flat turn using steerable forward and aft struts are employed what factors should I consider?

    Thanks
    Anup
     
  2. DCockey
    Joined: Oct 2009
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    Location: Midcoast Maine

    DCockey Senior Member

    University student design project?
     
  3. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    In order to establish the series you need data.
    Data of what the foil should do - so do you have any...oh wait, let's see:

    So...yes, YOU have all the information you need. All YOU need to do is select a series, any will do, that satisfies the above. That is YOUR choice as the designer. No one else's.

    It is called....designing!
     
  4. anuprdk
    Joined: May 2018
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    Location: india

    anuprdk Junior Member

    Last edited: May 10, 2018
  5. tspeer
    Joined: Feb 2002
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    Location: Port Gamble, Washington, USA

    tspeer Senior Member

    You can calculate the section data for 8e5 using Xfoil. You should calculate your own section data for all the Reynolds numbers so you ensure they are done with a consistent set of parameters. In Xfoil, I'd run them with free transition and 1<Ncrit<3 as well as fully turbulent (I like to set the trip at x=-0.025). You will also want to set CINC to TRUE so the minimum pressure is included in the polars. This will let you calculate the incipient cavitation speeds.

    I think you'll find that if you assume the flow is fully turbulent, then the minimum drag depends mainly on the thickness, and there's little difference for sections of different shape with the same thickness. And at 20 kt, cavitation is not going to be a big concern.

    With a 50 mm chord, you're going to need to ensure the machining is done very accurately, especially at the leading edge.
     

  6. anuprdk
    Joined: May 2018
    Posts: 9
    Likes: 0, Points: 1
    Location: india

    anuprdk Junior Member

    Thank you Sirs for the prompt response. Going to learn Xfoil
     
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