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A newly developed three dimensional multi-domain high order boundary element method (MDHOBEM) is applied to solve time domain ship motions in waves for ships advancing with forward speed, as well as the corresponding added wave resistances. By the method, fluid domain is decomposed by a regular control surface into inner and outer parts, in which Rankine panel method and transient Green function method are adopted respectively. By the MDHOBEM, the problem of highly oscillatory nature of transient Green function near waterline can be avoided due to substitution of Rankine source in inner domain. Fewer discrete quantities than in Rankine panel method is needed as transient Green function is employed in outer domain, and the radiation condition can be analytically satisfied as well. Boundary value problem of velocity potential is solved in a translational and inertial frame without use of moving mesh, implying it is a highly efficient approach. A mixed form of ship wave linearized or double body flow linearized free surface condition, and the according m -terms are employed in inner domain to treat the steady flow effects more accurately. The yielding hybrid boundary integral equations are discretized with bi-quadratic isoparametric high order elements to minimize discretization error. A Fortran code is originally developed, and is used to simulate wave-body interactions of both the wall-sided and flared hulls including mathematical Wigley-3 hull, Series60, and more realistic hull forms of KCS and S175. Convergence of spatial and temporal discretization, and size of inner domain are detailedly investigated beforehand. Results indicate the present numerical scheme has quite good robustness, and the inner free surface can be reduced to a rather small region comparing to Rankine panel method. The computed hydrodynamic coefficients, added wave resistance and ship motions by MDHOBEM are compared with model test data and results of classic boundary element methods including Rankine panel method, transient Green function method, and translating and pulsating Green function method. It manifests the MDHOBEM has quite good accuracy and needs less computational cost. [ABSTRACT FROM AUTHOR]

In this paper, we perform a comprehensive study of various semi-empirical methods using publicly accessible experimental data on added resistance in waves with different ship types and conditions. Based on the analysis results, a new method (So-called "Combined method") is proposed, combining two existing methods, which are available in arbitrary wave headings. The results from the two methods are combined smoothly using a tangent hyperbolic function according to wavelengths and wave headings. The coefficients constituting the function are tuned to minimize mean squared error between predictions and model experiments. Finally, the new Combined method is verified by full-scale measurements of a general cargo ship and a container ship, and it seems to give good agreement with measurements in all analysis areas, compared to existing semi-empirical methods. Especially, it showed better performance in estimating added wave resistance at high waves, resonance frequencies, arbitrary waves, and low speeds. • Investigated semi-empirical methods for added wave resistance using experimental data • Proposed a new method of combining the two results available in arbitrary waves • Showed improvement of the new method by validation with two ships' in-service data • Performed well at high waves, resonance frequencies, arbitrary waves, and low speeds [ABSTRACT FROM AUTHOR]

Abstract: In order to demonstrate the effect of oblique waves on ocean-going vessel behavior in realistic sea states, this paper addresses an effective and useful tool to predict the ship''s motion and propulsion system behavior with sufficient accuracy, considering the wave conditions on the operating route. Seakeeping model test was carried out with a freely running model in oblique waves in the ocean basin at the Marine Technology Centre, Trondheim, Norway. A time domain numerical simulation study was performed, and the results of the simulation are compared with the model test data. Due to the length limitation of the ocean basin, converged speed in waves cannot be achieved in all runs. A correction method is proposed in this paper to determine the converged speed from non-converged runs. The correction method is based on the condition that the converged speed in waves is dependent on the balance between resistance and propulsion force. [Copyright &y& Elsevier]

In this study, the hydrodynamic performance of a ship in terms of motions and resistance responses in calm water and in regular head waves is investigated for two loading conditions using a Fully Nonlinear Potential Flow (FNPF) panel method. The main focus is understanding the ship responses in a broad range of operational conditions. Comprehensive analyses of the motions and their correlation with the wave making resistance including their harmonics in waves are presented and compared against experimental data. The predicted motions compare well with experimental data but the resistance prediction is not quite as good. The natural frequencies for heave and pitch are estimated from a set of free decay motion simulations in calm water to provide a better insight into the ship behavior near resonance conditions in waves. Interestingly, in addition to the well known peak in the added wave resistance coefficient around wave lengths close to one ship length, a secondary peak is detected in the vicinity of wave lengths with half the ship length. • A Fully Nonlinear Potential Flow method (FNPF) is used. • A broad range of operational conditions in calm water and in waves are considered. • Ship motions and resistance harmonics are investigated. • Motions are predicted rather accurately compared to experiment, but not resistance. • A main and a secondary peaks of added wave resistance coefficient are observed. [ABSTRACT FROM AUTHOR]

Affected by the minimum power assessment requirements of the newbuilding energy efficiency design index (EEDI), added resistance of ships navigating in waves has been attracted more and more attention. By using the Green's function of three-dimensional translating pulsating source (3DTP), radiation/diffraction problems and ship motions are solved and good results are obtained. Based on these, the three-dimensional (3D) scattered energy approach to evaluate added wave resistance is proposed, which is combined with the radiated energy method and the Salvesen's weakly scattering assumption. It is reported in previous studies the computed added wave resistance is in reasonable agreement with experiment results on fine ship in medium wavelength waves. But for short-waves, the direct calculation cannot give precise result due to the limitation of the theory assumption. It is also question for long-waves case. A semi-empirical formula is proposed to correct the added wave resistance due to diffraction in short-waves. Considering the reflection attenuate phenomenon of waves with various wave length, a new approach with reflection ratio correction is hired in the formula. Finally, the modified formula is achieved that can be applied to directly calculate ship advancing in waves of various wavelength or full frequency range. With the comparison of calculation and model test results, the new correction method is verified and validated. It is also proved it fits not only for fine ship, but also for large blunt ship. • A new formula with reflection ratio correction is derived and hired in diffraction added wave resistance. • The insufficient of the directly calculation method on potential flow theory in short waves and in long waves is remedied. • Satisfactory agreements with experiment are obtained in various wave length. • The new approach could be applicated for various type of ship, not only fine ship, but also blunt ship. [ABSTRACT FROM AUTHOR]

This paper addresses the connection between added wave resistance and required propulsion power of ships, having focus on the early stage of new ship designs, notably tankers and bulk carriers. The paper investigates how mean added wave resistance affects the required torque of a fixed pitch propeller and thus also the operational conditions of a directly coupled main engine. The interest of the study has its background in the assessment of minimum propulsion power, and the study considers the prescriptive guidelines of the IMO as basis. Specifically, the study focuses on an assessment of the minimum forward speed attainable under consideration of the propeller light running margin and static load limits of engines in the early phase of new ship designs, where details of hull geometry are not available. The study considers three semi-empirical methods for predicting mean added wave resistance. All methods are known to be applied in the industry, emphasising that only methods relying solely on main particulars, together with information about sea state and advance speed, are of interest. The paper contains a case study used to illustrate the importance of the added wave resistance prediction with respect to the loading of the main engine. It is shown that, despite small absolute differences, the consequence in relation to the loading of the propeller and hereby the directly coupled main engine can be relatively large. Furthermore, the study illustrates that the propeller light running margin of a fixed pitch propeller directly coupled to the main engine has crucial influence on the attainable speed during adverse weather conditions. [ABSTRACT FROM AUTHOR]