ABSTRACT

Added wave resistance is the key parameter for estimating meteorological factor of Energy Efficiency Design Index, and is important for choosing suitable ship propulsion power. A practical numerical method, multi-domain high order boundary element method incorporated with three-dimensional energy radiated method, is originally proposed to evaluate added wave resistance in the present paper. Numerical program is developed for validation study and three types of hulls including mathematical Wigley-3, S175 and a full-formed tanker are employed as numerical example. Present results are in good agreement with model test data. Numerical investigation by comparing with classic boundary element method combined with near field and far field method are also carried out. It indicates the proposed numerical approach is robust and accurate, and is applicable for engineering use. Detailed discussions are also carried out.

INTRODUCTION

Added wave resistance is the key parameter for estimating meteorological factor of Energy Efficiency Design Index (EEDI), and would take 20∼40% of calm water resistance, so it is important for choosing suitable ship propulsion power. It is in fact longitudinal component of mean drift force. To compute second order wave force, one can use far field method. Maruo (1960, 1963), Newman (1967), Kashiwagi (2009), Liu et al. (2011), Joncquez (2009), Seo et al. (2013) carried out research into far field method. Far field method is derived in view of momentum conservation, and a control surface far enough from ship hull is usually needed in calculation. An alternative method is near field method, by which the second order force is computed by hydrodynamic integral on ship hull. Near field integral equation is derived by perturbation expansion and retaining second order terms. Joncquez (2009), Kim and Kim (2011), Seo et al. (2013), Chen and Duan (2016) applied near field method to compute added wave resistance. The integral equation of second order force is quite complicated and contains a large number of second order derivatives which are difficult for evaluating. A practical method is energy radiated method which follows energy principle that radiation energy in an encounter period behind the ship equals to the work done by average added resistance of ship. Energy radiated method is proposed by Gerritsma and Beukelman (1972), who adopted two dimensional hydrodynamic coefficients obtained by strip theory to compute added wave resistance. Hong et al. (2016) derived expression of three-dimensional energy radiated method based on added mass and damping coefficients computed with transiting and pulsating source Green function.

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