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.
Highlights
When a ship navigates in a seaway, there are various sources of additional resistance including the wind, waves, and rudder angle compared with the resistance of an advancing ship in calm water
To limit greenhouse gas emissions, the Marine Environment Protection Committee (MEPC) of the International Maritime Organization (IMO) has established regulations concerning the measurement of energy efficiency levels, such as the Energy Efficiency Design Index (EEDI)
The grid sensitivity was somewhat high for the present numerical method, and care must be taken to determine the total resistance of a ship, including the added resistance in short waves
Summary
When a ship navigates in a seaway, there are various sources of additional resistance including the wind, waves, and rudder angle compared with the resistance of an advancing ship in calm water. The CFD method can be utilized to study the added resistance in short waves of ships with different bow shapes above the still-water level. For this scenario, various methods have been applied to investigate the effect of different bow shapes on the added resistance in short waves. Orihara and Miyata [12] solved ship motions under regular head-wave conditions, and evaluated the added resistance of an SR-108 containership (typically known as an S175 containership) in waves using a CFD simulation method called WISDAM-X They provided computational and experimental results with different bow shapes for the model containership, and confirmed that its sharp bow shape provides a smaller added resistance in waves. The time-averaged added pressure was obtained from the time history of the added pressure on each triangular surface mesh, which represents the ship surface, and the distribution characteristics on the ship surface were investigated for each bow shape and wave amplitude
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