WAMIT dimensioning

Discussion in 'Hydrodynamics and Aerodynamics' started by kt787, May 8, 2013.

  1. kt787
    Joined: May 2013
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    kt787 New Member

    I want to calculate the radiation forces on an oscillating body in still water by calculating the convolution of the WAMIT radiation Impulse response function with the body velocity.
    My question is does anyone know how to dimensionalize the impulse response function which have a file extension _KR.1? The WAMIT manual states that the damping is dimensionalized by rho*omega but I am unsure what value of omega should I use?
  2. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    Omega is the frequency, the inverse of the period, in radians/sec. So omega corresponds to whatever periods you entered into the PER(i) array in the POT file.
  3. kt787
    Joined: May 2013
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    kt787 New Member

    Thank you. So should i multiply the impulse response function by rho*omega to dimensionalize it using this value of omega?

  4. Murdock86
    Joined: Oct 2012
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    Murdock86 Junior Member

    All values calculated in WAMIT are non-dimensionalised. These are indicated with an overbar above the symbol in the manual.

    To dimensionalise damping coefficients, one needs to multiply with the rho*omega* [(L)^k] value. Where L = non dimensianalising length used in GDF file parameter ULEN; k is mode-dependant as the manual describes.

    As jehardiman rightly states, omega is the instantaneous wave frequency in radians/sec.

    For example, if the instantaneous time period = 4 secs, the corresponding omega would be 2*pi/4 = 1.57 rads/sec. Do this over your frequency range and you'd get your dimensional damping graph.
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