Bilge keel load and hull pressure distribution on a rolling ship section with a high-order fractional step finite volume solver

Abstract

Bilge keel load and hull pressure distribution are investigated. For this purpose, harmonic excited rolls of the mid-section of a KVLCC2 fitted with one bilge keel are simulated by means of a high-order fractional step finite volume solver. Fourier analysis is employed to derive drag and inertia coefficients in Morison equation and the corresponding higher harmonic terms from bilge keel load. The calculated drag and inertia coefficients as well as positive and negative pressure coefficients are validated with some published numerical and experimental results. Influence of the roll amplitude and circular frequency, height and thickness of the bilge keel, and draught is presented. In results, drag and inertia coefficients is solely determined by KC number. Effect of draught, circular frequency and thickness of bilge keel is minuscule and negligible. Bilge keel load shows pronounced nonlinearity, which reveals the importance of the higher harmonic terms. Besides, drag coefficient and jump of the pressure coefficient satisfy the relationship assumed by Ikeda et al. (1977a). Positive pressure coefficient in front of bilge keel is KC-dependent at low KC number especially when KC < 6. The empirical method underestimates the positive pressure at low KC number and overestimates the negative pressure.