Force of Moving Water

  1. Does anyone know of an equation I may use to calculate the force of moving water? I am trying to theoretically workout the resistive force a vehicle would meet if it were to drive upstream (hydrodynamic drag).

    I am assuming the main parameters such an equation would include are water depth, water speed, water density and the surface area of the exposed parts of the vehicle such as the portion of its tyres submerged in the stream.

    Last edited: Jun 26, 2006
  2. jcsd
  3. Force=v*rate of change of mass
    F=Apv^2, where p = density of water, v=velocity of water, A=surface area
  4. Thank you very much, Harmony.
  5. I am wondering now if it is possible to use exactly the same equation for calculating aerodynamic drag as is used for calculating hydrodynamic drag?

    Instead of using a figure for air density, a figure for water density is employed. The coefficient of drag remains the same.

    What do you think?

    Aerodynamic drag is: F = 0.5PV²Cdf


    P = air density
    V = velocity
    Cd = coefficient of drag
    f = frontal area

    Edit: Of course the coefficient of drag would be specific to the part of the vehicle subjected to the flowing water.
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