Numerical analysis of added resistance on blunt ships with different bow shapes in short waves

Abstract

In this paper, a Cartesian-grid method is applied to investigate the added resistance of KRISO's very large crude oil carrier hull with a different bow, particularly in short incident waves. The wavelength is fixed as half of the ship length in all computations. In the present numerical method, a first-order fractional-step method is applied to the velocity-pressure coupling in the fluid domain, and the volume-of-fluid method is adopted to capture the fluid interface. The ship is embedded in a Cartesian grid, and the volume fraction of the ship inside the grid is calculated to identify the different phases in each grid. The sensitivity of the time window during post-processing as well as the number of solution grids is investigated. The computed added resistance is compared with experimental data. In addition, the characteristics of the surge force for different wave amplitudes are observed by comparing the wave elevation around the bow. Further, to compare the relative magnitude of higher harmonic components with respect to the magnitude of the first harmonic component, harmonic analyses of the time history of the surge force are performed. Based on the present numerical results, the effects of the wave amplitude and bow shape on added resistance for a short wavelength are observed. Finally, the distribution characteristics of time-averaged added pressure on the ship surface are investigated for each bow shape and wave amplitude.

Evaluation of the Effect of Container Ship Characteristics on Added Resistance in Waves

“…The authors concluded that it is of great importance to take into account the hull immersion angle when calculating the relative wave amplitude along the waterline on the example of container ships S175 and KCS (Kriso Container Ship), while it does not significantly affect the results of the analyzed Ro-Ro ship. Yang and Kim [18] have come to the similar conclusion by analyzing the bow shape of KVLCC2 (Korean Very Large Crude Carrier) above the waterline. Park et al [19] have investigated the effect of draft on added resistance in waves experimentally and numerically on the example of KVLCC2.…”

Numerical Study on Unsteady Pressure Distribution on Bulk Carrier in Head Waves with Forward Speed

“…To investigate the characteristic of added resistance in head waves more clearly, Figure 15 plots the time-averaged added pressure and the added local force in the longitudinal direction obtained using the Cartesian-grid method. In the previous study [17], the added pressure Δpk was defined as follows: The normalized values of first-harmonic component for the short-wave condition are less sensitive to wave steepness than that for the resonance condition. In other words, the first-harmonic component is proportional to the wave amplitude for the short-wave condition.…”

“…The verification and validation of the present Cartesian-grid method for wave-body interaction problems have been made in Yang and Kim [17] and Yang et al [21]. The sensitivity of time steps is less than the grid sensitivity and almost ignorable if the Courant-Friedrichs-Lewy (CFL) condition is satisfied.…”

“…In an experiment, it is relatively easy to measure hydrodynamic forces acting on a ship by a dynamometer, whereas the measurement of local variables, such as hydrodynamic Cartesian-grid method can be found in Yang and Kim [17], and the numerical procedure is briefly summarized here.…”

“…The volume fraction of a solid body is calculated by the transformation of a signed distance field between the ship surface and a grid point. The slip boundary condition is satisfied by a volume-weighted formula [17,21]:…”