scholarly journals Hull form optimization in the conceptual design stage considering operational efficiency in waves

2018 ◽  
Vol 233 (3) ◽  
pp. 745-759 ◽  
Author(s):  
Yoo-Won Jung ◽  
Yonghwan Kim
Keyword(s):  
Optimization Method ◽  
Operational Efficiency ◽  
Hydrodynamic Performance ◽  
Design Stage ◽  
Total Resistance ◽  
Added Resistance ◽  
Slender Body Theory ◽  
Hull Form ◽  
Weather Factor ◽  
Calm Water

This study focuses on the optimization of ship dimensions by considering hydrodynamic performance in waves. In actual seaways, a ship experiences speed loss due to environmental loads by waves and wind. Therefore, along with calm water resistance, speed loss in waves should be considered in the hull form design in order to improve operational efficiency in waves. However, a trade-off may be needed between total resistance on the ship and the speed loss in waves. To address this problem, Non-dominated Sorting Genetic Algorithm II, which is a multi-objective optimization method, is used to minimize the total resistance on a ship in seaways and the speed loss by additional resistance. In the optimization process, added resistance is predicted using a numerical method based on slender-body theory, Maruo’s far-field formulation, and an empirical formula for added resistance in short waves. The speed loss in waves, which can be expressed by a weather factor ( fw), is estimated using power–speed curves. This article introduces some examples of the sensitivity analysis of added resistance and speed loss in waves to the variations of ship dimensions. Finally, the optimization solutions on a Pareto front set are compared to a basis ship in terms of hull form, and the corresponding hydrodynamic performances are evaluated.

scholarly journals Study on Hull Optimization Process Considering Operational Efficiency in Waves

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 898
Author(s):  
Beom-Soo Kim ◽  
Min-Jae Oh ◽  
Jae-Hoon Lee ◽  
Yong-hwan Kim ◽  
Myung-Il Roh
Keyword(s):  
Water Resistance ◽  
Operational Efficiency ◽  
Free Form ◽  
Total Resistance ◽  
Added Resistance ◽  
Deformation Method ◽  
Cross Sectional ◽  
Hull Form ◽  
Strip Theory ◽  
Calm Water

This study investigates the optimization of the hull form of a tanker, considering the operational efficiency in waves, in accordance with the recent Energy Efficiency Design Index regulation. For this purpose, the total resistance and speed loss of the ship under representative sea conditions were minimized simultaneously. The total resistance was divided into three components: calm water resistance, added resistance due to wind, and to waves. The first two components were calculated using regression formulas, and the last component was estimated using the strip theory, far-field method, and the short-wave correction formula. Next, prismatic coefficient, waterline length, waterplane area, and flare angle were selected as design variables from the perspective of operational efficiency. The hull form was described as a combination of cross-sectional curves. A combination of the method shifting these sections in the longitudinal direction and the Free-Form Deformation method was used to deform the hull. As a result of applying the non-dominated sorting genetic algorithm to a tanker, the hull was deformed thinner and longer, and it was determined that the total resistance and speed loss were reduced by 3.58 and 10.2%, respectively. In particular, the added resistance due to waves decreased significantly compared to the calm water resistance, which implies that the present tendency differs from conventional ship design that optimizes only the calm water resistance.

Numerical Analysis of the Influence of Above-Water Bow Form on Added Resistance Using Nonlinear Slender Body Theory

2005 ◽  
Vol 49 (03) ◽  
pp. 191-206
Author(s):  
Hajime Kihara ◽  
Shigeru Naito ◽  
Makoto Sueyoshi
Keyword(s):  
Three Dimensional ◽  
Wave Force ◽  
Slender Body ◽  
Added Resistance ◽  
Slender Body Theory ◽  
Hull Form ◽  
Nonlinear Properties ◽  
Head Waves ◽  
The Time Domain ◽  
Body Theory

A nonlinear numerical method is presented for the prediction of the hydrodynamic forces that act on an oscillating ship with a forward speed in head waves. A "parabolic" approximation of equations called "2.5D" or "2D+T" theory was used in a three-dimensional ship wave problem, and the computation was carried out in the time domain. The nonlinear properties associated with the hydrostatic, hydrodynamic, and Froude-Krylov forces were taken into account in the framework of the slender body theory. This work is an extension of the previous work of Kihara and Naito (1998). The application of this approach to the unsteady wave-making problem of a ship with a real hull form is described. The focus is on the influence of the above-water hull form on the horizontal mean wave force. Comparison with experimental results demonstrates that the method is valid in predicting added resistance. Prediction of added resistance for blunt ships is also shown by example.

Sailing Yacht Performance in Calm Water and in Waves

1993 ◽  
Author(s):  
J. Gerritsma ◽  
J. A. Keuning ◽  
A. Versluis
Keyword(s):  
Model Experiment ◽  
Irregular Waves ◽  
Current Interest ◽  
Added Resistance ◽  
Hull Form ◽  
Wide Range ◽  
Calm Water ◽  
Added Resistance In Waves ◽  
Sailing Yacht ◽  
Calculated Analysis

The Delft systematic Yatch Hull Series has been extended to a total of 39 hull form variations, covering a wide range of length displacement ratios and other form of parameters. The total set of model experiment results, upright and heeled resistance as well as sideforce and stability, had been analysed and polynomial expressions to approximate these quantities are presented. In view of the current interest in the performance of sailing yachts in waves, the added resistance in irregular waves of 8 widely different hull variations has been calculated. Analysis of the results shows that the added resistance in waves strongly depends on the product of displacement-length ratio and the gyradius of the pitching motion.

Numerical and Experimental Analysis of Added Resistance of Ships in Waves

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Ould el Moctar ◽  
Sebastian Sigmund ◽  
Jens Ley ◽  
Thomas E. Schellin
Keyword(s):  
Water Resistance ◽  
Frictional Resistance ◽  
Medium Size ◽  
Total Resistance ◽  
Added Resistance ◽  
Short Waves ◽  
Radiation Forces ◽  
Calm Water ◽  
Added Resistance In Waves ◽  
Force Components

Two Reynolds-Averaged Navier–Stokes (RANS) based field methods numerically predicted added resistance in regular head waves for a 14,000 TEU containership and a medium size cruise ship. Long and short waves of different frequencies were considered. Added resistance was decomposed into diffraction and radiation force components, whereby diffraction forces were obtained by restraining the ship in waves and radiation forces by prescribing the motions of the ship in calm water. In short waves, the diffraction part of total resistance was dominant as almost no ship motions were induced. In long waves, the sum of diffraction and radiation forces exceeded total resistance, i.e., the interaction of these two force components, which caused the reduction of total resistance, needed to be accounted for. Predictions were compared with model test measurements. Particular emphasis was placed on the following aspects: discretization errors, frictional resistance as part of total added resistance in waves, and diffraction and radiation components of added resistance in waves. Investigations comprised two steps, namely, a preliminary simulation to determine calm water resistance and a second simulation to compute total resistance in waves, always using the same grids. Added resistance was obtained by subtracting calm water resistance from total averaged wave resistance. When frictional resistance dominated over calm water resistance, which holds for nearly all conventional ships at moderate Froude numbers, high grid densities were required in the neighborhood surrounding the hull as well as prism cells on top of the model's surface.

Numerical and Experimental Analysis of Added Resistance of Ships in Waves

2015 ◽  
Author(s):  
Ould el Moctar ◽  
Sebastian Sigmund ◽  
Thomas E. Schellin
Keyword(s):  
Water Resistance ◽  
Frictional Resistance ◽  
Medium Size ◽  
Total Resistance ◽  
Added Resistance ◽  
Short Waves ◽  
Radiation Forces ◽  
Calm Water ◽  
Added Resistance In Waves ◽  
Force Components

A RANS-based field method numerically predicted added resistance in regular head waves for a 14000 TEU containership (Duisburg Test Case) and a medium-size cruise ship. We concentrated our investigations on short waves. For different frequencies, we decomposed added resistance into diffraction and radiation force components, whereby diffraction forces were obtained by restraining the ship in waves and radiation forces, by prescribing the motions of the ship in calm water. In short waves, the diffraction part of total resistance was dominant as almost no ship motions were induced. In long waves, the sum of diffraction and radiation forces exceeded total resistance, i.e., the interaction of these two force components, which caused the reduction of total resistance, had to be accounted for. Predictions were compared with model test measurements. Particular emphasis was placed on the following aspects: discretization errors, frictional resistance as part of total added resistance in waves, diffraction and radiation components of added resistance in waves, and the influence of surge motion on added resistance. Investigations comprised two steps, namely, a preliminary simulation to determine calm-water resistance and a second simulation to compute total resistance in waves, always using the same grids. Added resistance was obtained by subtracting calm-water resistance from total averaged wave resistance. When frictional resistance dominated calm-water resistance, which holds for nearly all conventional ships at moderate Froude numbers, high grid densities were required in the neighborhood surrounding the hull.

Comparative Performance of Optimum High Speed SWATH and Semi-SWATH in Calm Water and in Waves

2015 ◽  
Author(s):  
S. Brizzolara ◽  
G. Vernengo ◽  
L. Bonfiglio ◽  
D. Bruzzone
Keyword(s):  
High Speed ◽  
Hydrodynamic Performance ◽  
Forward Speed ◽  
Comparative Performance ◽  
Hull Form ◽  
High Speeds ◽  
Head Waves ◽  
Calm Water ◽  
Minimization Algorithms ◽  
Ranse Solver

The hydrodynamic performance of unconventional SWATH and Semi-SWATH for high speed applications are analyzed and compared in this paper. Bare hull resistance in calm water is estimated by an inviscid boundary element method with viscous corrections and verified by a fully turbulent, multiphase unsteady RANSE solver. Motions response in head waves, calculated by a frequency domain 3D panel method with forward speed effects are also evaluated and compared. Both considered hulls are the best designs coming from full parametric hull form optimization procedures, based on CFD solvers for the estimation of their hydrodynamic performance and driven by evolutionary minimization algorithms. The SWATH has twin parabolic struts and an unconventional underwater shape, the semi-SWATH has a slender triangular waterline, a bulbous shape in the entrance body which gradually morph into a U-section with a shallow transom in the run body. In general, as expected, the Semi-SWATH hull shows a lower drag at high speeds while the single strut SWATH is superior at lower speeds. As regards seakeeping, the SWATH shows unbeatable lower pitch and heave motions in shorter waves, where the Semi-SWATH evidences a double peaked RAO. More detailed analysis and conclusion are drawn in the paper.

Study of Wave Added Resistance on Wigley Ship

2013 ◽  
Vol 468 ◽  
pp. 105-109
Author(s):  
Tao Sun ◽  
Ming Hui Yuan ◽  
Wei Wang ◽  
Nan Ye
Keyword(s):  
Total Resistance ◽  
Added Resistance ◽  
Ship Model ◽  
Seakeeping Performance ◽  
Head Waves ◽  
Free Model ◽  
Calm Water ◽  
Significant Research ◽  
Energy Consuming ◽  
Hydrodynamic Potential

Global warming is becoming a serious problem nowadays. The emissions of greenhouse gas from vessels draw great attentions. As a significant research part of vessel seakeeping performance, resistance capability exert pretty effect on energy consuming. A Wigley ship model is set as the object to compute constraint and free model in calm water and head waves on resistance and hydrodynamic potential coefficients by STAR-CCM. Differences are discussed between both models. Effects on calculation of hydrostatic resistance ignoring trim and heave are revealed .Wave added resistance of free model is computed and compared at different amplitudes and wavelengths. How trim and heave matter the computed results are discussed. So does how wavelength and amplitudes influence total resistance is considered.

scholarly journals Hydrodynamic study of the influence of bulbous bow design for an Offshore Patrol Vessel using Computational Fluid Dynamics

2018 ◽  
Vol 11 (22) ◽  
pp. 29
Author(s):  
Luis Leal ◽  
Edison Flores ◽  
David Fuentes ◽  
Bharat Verma
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Hydrodynamic Performance ◽  
Design Stage ◽  
Hull Form ◽  
Preliminary Design Stage ◽  
Hydrodynamic Study ◽  
Resistance Curves ◽  
Design Speed ◽  
Bulbous Bow

The resistance of a ship is of vital importance in giving greater viability to the development of a design project, since at lower ship resistance, the power demand to achieve a desired design speed will be lower which will reduce the amount of power to be installed in the ship resulting in lower fuel consumption. The use of computational fluid dynamics to analyze and optimize hull form and its appendages permits the hydrodynamic performance of the ship to be improved from the early design stages, allowing improvements to the hull shape and appendages. This paper shows a qualitative analysis which was performed to reduce the resistance of the OPVMKII (Second Generation Offshore Patrol Vessel) in its preliminary design stage by means of designing and integrating three types of bulbous bow with the ship´s hull and analyzing the resistance curves obtained using computational fluid dynamics.

Hull Form Optimization for Hydrodynamic Performance

2004 ◽  
Vol 41 (04) ◽  
pp. 167-182
Author(s):  
Gregory J. Grigoropoulos
Keyword(s):  
Water Resistance ◽  
Optimization Procedure ◽  
Hydrodynamic Performance ◽  
Hull Form ◽  
Principal Characteristics ◽  
Calm Water ◽  
Rough Water ◽  
Hull Forms ◽  
Scaled Models ◽  
Formal Optimization

A method for optimizing hull forms with respect to their hydrodynamic performance in calm and rough water is presented. The method is based on an initial optimization of a parent hull form for seakeeping and the improvement of the resulting optimum hull form for calm water resistance. In the first part of the method, variant hull forms differing from a parent in the main dimensions and/or in one or more hull form parameters, such as CWP, LCF, CB, LCB, KB, CP, are automatically generated and their seakeeping qualities evaluated. When appropriate ranges for the principal characteristics and parameters of the hull form under investigation are prescribed, a formal optimization procedure is used to obtain the variant with the best seakeeping behavior. The weighted sum of the resonant values of selected ship responses for a number of ship speeds and headings in regular waves forms the objective function. The Hooke and Jeeves algorithm is used to accomplish the optimization. The procedure results in a set of trends regarding the proposed variations of the selected hull form parameters, within the specified constraints. These trends are then applied on the parent hull to derive an optimized hull form with fair lines. Subsequently, this hull form can be locally modified to improve its calm water resistance or, as it should be done, its propulsion characteristics. The applicability of the method is demonstrated in two cases: a conventional reefer ship and a naval destroyer. Scaled models of the parent and the optimized hull forms have been tested for calm water resistance and seakeeping. In both cases the validity of the methodology is demonstrated.

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

2020 ◽  
Vol 8 (9) ◽  
pp. 696
Author(s):  
Ivana Martić ◽  
Nastia Degiuli ◽  
Andrea Farkas ◽  
Ivan Gospić
Keyword(s):  
Point Of View ◽  
Irregular Waves ◽  
Design Stage ◽  
Radius Of Gyration ◽  
Container Ship ◽  
Added Resistance ◽  
Head Waves ◽  
Calm Water ◽  
Added Resistance In Waves ◽  
Longitudinal Position

Added resistance in waves is one of the main causes of an increase in required power when a ship operates in actual service conditions. The assessment of added resistance in waves is important from both an economic and environmental point of view, owing to increasingly stringent rules set by the International Maritime Organization (IMO) with the aim to reduce CO2 emission by ships. For that reason, it is desirable to evaluate the added resistance in waves already in the preliminary ship design stage both in regular and irregular waves. Ships are traditionally designed and optimized with respect to calm water conditions. Within this research, the effect of prismatic coefficient, longitudinal position of the centre of buoyancy, trim, pitch radius of gyration, and ship speed on added resistance is investigated for the KCS (Kriso Container Ship) container ship in regular head waves and for different sea states. The calculations are performed using the 3D panel method based on Kelvin type Green function. The results for short waves are corrected to adequately take into account the diffraction component. The obtained results provide an insight into the effect of variation of ship characteristics on added resistance in waves.

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