Enhancement of asymptotic formula for added resistance of ships in short waves

This paper introduces a practical formula for added resistance in short waves. Particularly, the formulation introduced by Faltinsen et al. (1980) is modified to consider the three aspects: the finite draught of ships, the local steady velocity, and the shape above still-water-level (SWL). First, an additional term due to the finite draught of ships is derived by subtracting the integration of velocity square terms along the vertical control surface from the ships draught to the negative infinite. Second, a new local steady velocity is proposed, which includes the variation of sectional area. Third, the bow shape above SWL is considered by introducing the ratio of bluntness coefficients at the mean level of steady waves and SWL. The mean level of steady waves is approximately calculated based on the steady wave elevation of an advancing wedge-shaped body in calm water. The effect of each modification has been investigated and compared to experimental results and other empirical formulae of added resistance in short waves. Finally, a practical approach to combine the modified formula and the existing computation method for the added resistance in an overall wavelength range is presented.