Added Resistance in Waves and Amplitude Function Expressing a Ship Hull Form

In this study, numerical computation was carried out for evaluating the effects of the design parameter variations on the added resistance of Aframax tanker in head seas. The design of experiments (DOE) was used to efficiently conduct the numerical simulations with the hull form variations and save computational resources. A computational fluid dynamics (CFD) code based on the continuity and Reynolds averaged Navier-Stokes (RANS) equation was used for the numerical simulation. The simulation was performed in a short wave condition where the wave length was half of the ship length, which is expected to be most frequent in the vessel operation. Five design parameters of fore-body hull form were selected for the variations: design waterline length (DWL), bulbous bow height (BBH), bulbous bow volume (BBV), bow flare angle (BFA) and bow entrance angle (BEA). Each parameter had two levels in the variations, thus total 32 cases were designed initially. The results of the numerical simulations were analyzed statistically to determine the main effects and correlations in the five design parameters variations. Among them, the most significant parameter that influences on the added resistance in waves was DWL, followed by BBV and BEA. The other parameters had little effects on the added resistance in waves. By the computations, it was revealed that Extending DWL and decreasing BEA promoted the reflection of waves more toward the side than forward. In addition, there existed two-way interactions for the following two-factor combinations: DWL-BFA, DWL-BEA, DWL-BBV, BBH-BBV.

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Sailing Yacht Performance in Calm Water and in Waves

10.5957/csys-1993-001 ◽

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.

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Experimental investigation on the added resistance of modified KVLCC2 hull forms with different bow shapes

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/1475090216643981 ◽

2016 ◽

Vol 231 (2) ◽

pp. 395-410

Author(s):

Jaehoon Lee ◽

Dong-Min Park ◽

Yonghwan Kim

Keyword(s):

Model Tests ◽

Green Water ◽

Added Resistance ◽

Hull Form ◽

Motion Responses ◽

Wide Range ◽

Added Resistance In Waves ◽

Design Speed ◽

Hull Forms ◽

Motion Amplitude

The effect of different bow shapes on the added resistance in waves was observed through a series of model tests. To this end, three different hull forms of KRISO Very Large Crude Carrier 2 were considered: an original hull form and two modified hulls with different bow shapes, called ax-bow and leadge-bow. The model tests were conducted for a wide range of wavelengths with two wave amplitudes in a regular head-sea condition at the design speed. Each test condition was imposed at least twice in order to check the repeatability of measurement, considering the uncertainties in model test and the nonlinear nature of the added resistance. This article introduces a preliminary study on the effects of surge motion, amplitude of incident wave, and green-water allowance around bow region. This article briefly includes the uncertainty analysis of recent study regarding the performance of the original hull. Based on the results of the experimental study for three different bow shapes, the parameters which influence the added resistance and motion responses are discussed.

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Added Resistance in Seaways and its Impact on Yacht Performance

10.5957/csys-2007-016 ◽

2007 ◽

Author(s):

Kai Graf ◽

Marcus Pelz ◽

Volker Bertram ◽

H. Söding

Keyword(s):

Strong Impact ◽

Wave Spectra ◽

Linear Extensions ◽

Added Resistance ◽

Optimum Length ◽

Prediction Program ◽

Strip Theory ◽

Velocity Prediction ◽

Added Resistance In Waves ◽

Response Amplitude Operators

A method for the prediction of seakeeping behaviour of sailing yachts has been developed. It is based on linear strip theory with some non-linear extensions. The method is capable to take into account heeling and yawing yacht hulls, yacht appendages and sails. The yacht's response amplitude operators (RAO) and added resistance in waves can be predicted for harmonic waves as well as for natural wave spectra. The method is used to study added resistance in seaways for ACC-V5 yachts of varying beam. Results are used for further VPP investigations. The AVPP velocity prediction program is used to study optimum length to beam ratio of the yachts depending on wind velocity and upwind to downwind weighting. This investigation is carried out for flat water conditions as well as for two typical wave spectra. The results show that taking into account added resistance in seaways has a strong impact on predicted performance of the yacht.

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The Performance of Sailing Yachts in Oblique Seas

Marine Technology and SNAME News ◽

10.5957/mt1.1974.11.4.383 ◽

1974 ◽

Vol 11 (04) ◽

pp. 383-392

Author(s):

David R. Pedrick

Keyword(s):

Wave Length ◽

Added Resistance ◽

Regular Waves ◽

Sea State ◽

Hull Form ◽

Rough Water ◽

Rational Procedure ◽

The Difference ◽

Relationship Of ◽

The Relationship

The difference in the effects of rough water on similar sailing yachts has been one of the intriguing puzzles that sailors, designers, and researchers have long tried to understand. It is not uncommon for two yachts of equal performance in smooth-sea conditions to have their speed or pointing ability reduced by different amounts when encountering waves. To investigate the causes of such behavior, it is important to have a rational procedure to analyze how changes in hull form, weight distribution, rig, and other design features affect the speed and motions of sailing yachts. This paper discusses the relationship of wind to rough water and of motions and added resistance to wave length and height. It then describes a procedure to predict motions, sailing speed, and speed-made-good to windward in realistic windward sailing conditions. The procedure utilizes results of heeled and yawed model tests of 12-metre yachts in oblique regular waves to predict performance in a Pierson-Moskowitz sea state corresponding closely to the equilibrium true wind speed.

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An Integrated Ship Re-Design/Modification Strategy

10.3940/rina.ijme.2019.a1.509 ◽

2019 ◽

Vol 161 (A1) ◽

Keyword(s):

Computer Aided Design ◽

Modular Design ◽

Ship Hull ◽

Cfd Model ◽

Hull Form ◽

Design Modification ◽

Technical Parameters ◽

Computational Fluid Dynamics Cfd ◽

Bulbous Bow ◽

Aided Design

Herein, we present an integrated ship re-design/modification strategy that integrates the ‘Computer-Aided Design (CAD)’ and ‘Computational Fluid Dynamics (CFD)’ to modify the ship hull form for better performance in resistance. We assume a modular design and the ship hull form modification focuses on the forward module (e.g. bulbous bow) and aft module (e.g. stern bulb) only. The ship hull form CAD model is implemented with NAPA*TM and CFD model is implemented with Shipflow**TM. The basic ship hull form parameters are not changed and the modifications in some of the technical parameters because of re-designed bulbous bow and stern bulb are kept at very minimum. The bulbous bow is re-designed by extending an earlier method (Sharma and Sha (2005b)) and stern bulb parameters for re-design are computed from the experience gained from literature survey. The re-designed hull form is modeled in CAD and is integrated and analyzed with Shipflow**TM. The CAD and CFD integrated model is validated and verified with the ITTC approved recommendations and guidelines. The proposed numerical methodology is implemented on the ship hull form modification of a benchmark ship, i.e. KRISO container ship (KCS). The presented results show that the modified ship hull form of KCS - with only bow and stern modifications - using the present strategy, results into resistance and propulsive improvement.

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Computation of Wave Added Resistance by Control Surface Integration

Volume 7: Ocean Engineering ◽

10.1115/omae2016-54353 ◽

2016 ◽

Cited By ~ 4

Author(s):

Zhiyuan Pan ◽

Torgeir Vada ◽

Kaijia Han

Keyword(s):

Free Surface ◽

Near Field ◽

Momentum Conservation ◽

Ship Hull ◽

Control Surface ◽

Floating Body ◽

Added Resistance ◽

Time Step ◽

Rankine Source ◽

Linearization Methods

A time domain Rankine source solver is extended to compute the wave added resistance of ships. The proposed approach applies the momentum conservation principle on the near field fluid volume enclosed by the wet surface of a floating body, the free surface and a control surface. The wave added resistance is then calculated by the integration over the control surface of the fluid velocities and free surface elevations. To be able to incorporate the proposed method with the Rankine source code, an interpolation scheme has been developed to compute the kinematics for the off-body points close to (or on) the free surface. Two Wigley ship models, a containership model S175 and a tanker model KVLCC2 are used to validate the present method. In general good agreement is found comparing with the model test data. The convergence behavior is examined for the proposed method including the selection of the time step and location of the control surface. Both Neumann-Kelvin and double body linearization methods are evaluated with the proposed method. It is found that the Neumann-Kelvin linearization can only be applied for slender ship hull, whereas double body method fits also for blunt ships. It is suggested to apply the proposed method with double body linearization to evaluate the wave added resistance of ships with a control surface close to the ship hull.

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