The Effect of Bow Steepness and Flare on the Resistance of Sailing Yachts in Calm Water and Waves

2001 ◽  
Author(s):  
J. A. Keuning ◽  
R. Onnink ◽  
A. Damman
Keyword(s):  
Water Resistance ◽  
Added Resistance ◽  
University Of Technology ◽  
Head Waves ◽  
Master Thesis ◽  
Calm Water ◽  
Added Resistance In Waves ◽  
Bow Flare ◽  
Sailing Yacht ◽  
Resistance Performance

In this paper some results are presented of two studies carried out at the Ship hydromechanics Department of the Delft University of Technology: one, on the influence of an increase of stem steepness of a sailing yacht, and another, which was largely carried out by T.J.E. Tincelin as part of his master thesis at Delft University of Technology, on the effect of above waterline bow flare are presented. To investigate the influence of bow steepness a model of the Delft Systematic Yacht Hull Series (DSYHS) has been used as a parent model of a new small subseries with two additional derivatives each with increased bow steepness. The influence on both the calm water resistance and the added resistance in head waves has been investigated. To investigate the influence of bow flare, two models of a typical "Open 60" design have been used: one "normal" and one with almost no flare in the bowsections. These have been tested in calm water and in both head- and following­waves to investigate the effects of this difference in bow shape on the calm water resistance, on added resistance in waves, and on the relative motions at the bow. The results are presented and some comparisons with calculations made. Also some general conclusions with respect to resistance, performance and safety are drawn.

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.

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.

A New Technique for Testing a Sailing Yacht in Waves

1991 ◽  
Author(s):  
G. K. Kapsenberg
Keyword(s):  
Degrees Of Freedom ◽  
Water Resistance ◽  
Ship Motions ◽  
Added Resistance ◽  
Regular Waves ◽  
Six Degrees Of Freedom ◽  
Resistance Increase ◽  
Calm Water ◽  
Sailing Yacht ◽  
A New Technique

A new experimental technique is presented to test sailing yachts in waves. The method is suitable for the investigation of ship motions in all six degrees of freedom and added resistance for the close hauled condition. Measurements can be made both in regular waves and in irregular seas. The technique has been tried out on a model of a 12-Meter class yacht and showed a resistance increase for the yacht sailing to windward in a wind generated sea of 90% of the calm water resistance.

scholarly journals Tank Tests with a Scaled Model of a BOC-50 Sailing Yacht Model in Calm Water and in Regular and Random Head Waves

2015 ◽  
Vol 5 (6) ◽  
Author(s):  
Dimitrios Liarokapis ◽  
Konstantina Sfakianaki ◽  
Giannis Papantonatos ◽  
Gregory Grigoropoulos
Keyword(s):  
Scaled Model ◽  
Head Waves ◽  
Calm Water ◽  
Sailing Yacht

Experiments and Computations for KCS Added Resistance for Variable Heading

2015 ◽  
Author(s):  
Hamid Sadat-Hosseini ◽  
Serge Toxopeus ◽  
Dong Hwan Kim ◽  
Teresa Castiglione ◽  
Yugo Sanada ◽  
...  
Keyword(s):  
Surface Profile ◽  
Engine Performance ◽  
Head Wave ◽  
Added Resistance ◽  
Local Flow ◽  
Wake Field ◽  
Head Waves ◽  
Calm Water ◽  
Free Surface Profile ◽  
Peak Location

Experiments, CFD and PF studies are performed for the KCS containership advancing at Froude number 0.26 in calm water and regular waves. The validation studies are conducted for variable wavelength and wave headings with wave slope of H/λ=1/60. CFD computations are conducted using two solvers CFDShip-Iowa and STAR-CCM+. PF studies are conducted using FATIMA. For CFD computations, calm water and head wave simulations are performed by towing the ship fixed in surge, sway, roll and yaw, but free to heave and pitch. For variable wave heading simulations, the roll motion is also free. For PF, the ship model moves at a given speed and the oscillations around 6DOF motions are computed for variable wave heading while the surge motion for head waves is restrained by adding a very large surge damping. For calm water, computations showed E<4%D for the resistance,<8%D for the sinkage, and <40%D for the trim. In head waves with variable wavelength, the errors for first harmonic variables for CFD and PF computations were small, <5%DR for amplitudes and <4%2π for phases. The errors for zeroth harmonics of motions and added resistance were large. For the added resistance, the largest error was for the peak location at λ/L=1.15 where the data also show large scatter. For variable wave heading at λ/L=1.0, the errors for first harmonic amplitudes were <17%DR for CFD and <26%DR for PF. The comparison errors for first harmonic phases were E<24%2π. The errors for the zeroth harmonic of motions and added resistance were again large. PF studies for variable wave headings were also conducted for more wavelength condition, showing good predictions for the heave and pitch motions for all cases while the surge and roll motions and added resistance were often not well predicted. Local flow studies were conducted for λ/L=1.37 to investigate the free surface profile and wake field predicted by CFD. The results showed a significant fluctuation in the wake field which can affect the propeller/engine performance. Additionally it was found that the average propeller inflow to the propeller is significantly higher in waves.

scholarly journals Full-Scale CFD Analysis of Double-M Craft Seakeeping Performance in Regular Head Waves

2021 ◽  
Vol 9 (5) ◽  
pp. 504
Author(s):  
Deniz Ozturk ◽  
Cihad Delen ◽  
Simone Mancini ◽  
Mehmet Ozan Serifoglu ◽  
Turgay Hizarci
Keyword(s):  
Full Scale ◽  
Stokes Wave ◽  
Added Resistance ◽  
Motion Responses ◽  
Seakeeping Performance ◽  
Head Waves ◽  
Calm Water ◽  
Maximum Improvement ◽  
Fifth Order ◽  
Regular Head Waves

This study presents the full-scale resistance and seakeeping performance of an awarded Double-M craft designed as a 15 m next-generation Emergency Response and Rescue Vessel (ERRV). For this purpose, the Double-M craft is designed by comprising the benchmark Delft 372 catamaran with an additional center and two side hulls. First, the resistance and seakeeping analyses of Delft 372 catamaran are simulated on the model scale to verify and compare the numerical setup for Fr = 0.7. Second, the seakeeping performance of the full-scale Double-M craft is examined at Fr = 0.7 in regular head waves (λ/L = 1 to 2.5) for added resistance and 2-DOF motion responses. The turbulent flow is simulated by the unsteady RANS method with the Realizable Two-Layer k-ε scheme. The calm water is represented by the flat VOF (Volume of Fluid) wave, while the incident long waves are represented by the fifth-order Stokes wave. The residual resistance of the Double-M craft is improved by 2.45% compared to that of the Delft 372 catamaran. In the case of maximum improvement (at λ/L = 1.50), the relative added resistance of the Double-M craft is 10.34% lower than the Delft 372 catamaran; moreover, the heave and pitch motion responses were 72.5% and 35.5% less, respectively.

Approximation of the Calm Water Resistance on a Sailing Yacht Based on the 'Delft Systematic Yacht Hull Series'

1999 ◽  
Author(s):  
J. A. Kenning ◽  
U. B. Sonnenberg
Keyword(s):  
Water Resistance ◽  
Force Production ◽  
Data Set ◽  
Side Force ◽  
Prediction Program ◽  
Resistance Increase ◽  
The Past ◽  
Calm Water ◽  
Velocity Prediction ◽  
Sailing Yacht

Over the past years a considerable extension has been given to the Delft Systematic Yacht Hull Series (DSYHS) The DSYHS data set now contains information about both the bare hull and appended hull resistance in the upright and the heeled condition, the resistance increase due to the longitudinal trimming moment of the sails, the side force production and induced resistance due to side force at various combinations of forward speeds, leeway angles and heeling angles. New formulations for the relevant hydrodynamic forces as function of the hull geometry parameters have been derived to be able to deal with a larger variety of yacht hull shapes and appendage designs. During the past two years some results of this research have already been published. In the present paper an almost complete picture of the relevant expressions which may be used in a Velocity Prediction Program (VPP) will be presented.

Experimental Study on Seakeeping Performance of a Catamaran with Asymmetric Demi-Hulls

2014 ◽  
Vol 66 (2) ◽  
Author(s):  
S. Ikezoe ◽  
N. Hirata ◽  
H. Yasukawa
Keyword(s):  
Experimental Study ◽  
Ship Motion ◽  
Added Resistance ◽  
Scaled Model ◽  
Seakeeping Performance ◽  
Head Waves ◽  
Lateral Space ◽  
Design Speed ◽  
Resistance Performance ◽  
Regular Head Waves

To capture the seakeeping performance of a catamaran with asymmetric demi-hulls, tank tests were carried out in regular head waves using a scaled model with 2.036 m in length. The lateral space between the demi-hulls was changed in the tests as W/B=2.55, 2.90 and 3.25, where W denotes breadth overall and B the breadth of the demi-hull. Also, two models with different water lines of inside flat and outside round (IF-type) and of outside flat and inside round (OF-type) were used. OF-type is superior to IF-type in both ship motion and added resistance performances in waves at the design speed. In IF-type series, the smallest clearance, W/B=2.55 is the best in the added resistance performance.

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