The Morison equation vs. diffraction analysis in determining wave force on piles

The choice between Morison's equation and diffraction analysis in determining the wave forces on piles depends on the ratio between the diameters of piles to wavelength. If the ratio between diameters of piles to wavelength is less than 0.2, Morison equation is typically recommended. Reason behind this is that effect of viscosity and separation is significant below this ratio. Quite the reverse, if the ratio between diameters of piles to wavelength exceeds 0.2, waves are scattered with negligible occurrence of separation. Diffraction analysis is adopted to calculate the wave forces on piles.