scholarly journals Mean Drift Forces on Vertical Cylindrical Bodies Placed in Front of a Breakwater

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 148
Author(s):  
Dimitrios Konispoliatis ◽  
Spyridon Mavrakos
Keyword(s):  
Hydrodynamic Interaction ◽  
Momentum Conservation ◽  
Direct Integration ◽  
Regular Waves ◽  
Method Of Images ◽  
Experimental Campaign ◽  
Vertical Drift ◽  
Vertical Breakwater ◽  
Drift Forces ◽  
Interaction Phenomenon

This paper presents a numerical and experimental investigation of the second-order steady horizontal and vertical drift forces acting on cylindrical bodies in regular waves. The examined bodies are either kept restrained in front of a vertical breakwater or are considered free- floating when alone in the wave field. Two principally different approaches for mean drift forces determination are described: the momentum conservation principle and the direct integration of all pressure contributions upon the instantaneous wetted surface of the bodies, whereas, for the solution of the associated diffraction and motion radiation problems, analytical and panel methodologies are applied. The hydrodynamic interaction phenomenon between the bodies and the adjacent breakwater are taken into account by using the method of images. Theoretical and numerical results, concerning the horizontal and the vertical drift forces, are presented and compared with each other. Furthermore, additional comparisons are made with experimental data obtained during an experimental campaign at French research institute for exploitation of the sea (IFREMER), in France.

A Strip Method for Lateral Drift Force of a Semisubmersible

1985 ◽  
Vol 107 (3) ◽  
pp. 329-334
Author(s):  
C. H. Kim ◽  
W. Bao
Keyword(s):  
Experimental Data ◽  
Hydrodynamic Interaction ◽  
Three Dimensional ◽  
Source Distribution ◽  
Regular Waves ◽  
Dimensional Theory ◽  
Lateral Drift ◽  
Drift Force ◽  
Twin Hulls ◽  
Drift Forces

This paper presents the results of an application of a strip technique for the prediction of the lateral drift forces on a semisubmersible platform floating in oblique regular waves. The method employs Maruo’s formula and source distribution technique, without taking account of the hydrodynamic interaction between the twin hulls and columns of the semisubmersible. Overall the strip technique shows a more favorable correlation with the experimental data than the three-dimensional theory. It is, however, premature to conclude that the technique has been fully validated.

scholarly journals Prediction of the Side Drift Force of Full Ships Advancing in Waves at Low Speeds

2020 ◽  
Vol 8 (5) ◽  
pp. 377 ◽  
Author(s):  
Shukui Liu ◽  
Apostolos Papanikolaou
Keyword(s):  
Empirical Formula ◽  
Experimental Results ◽  
Regular Waves ◽  
Short Waves ◽  
Wave Parameters ◽  
Preliminary Validation ◽  
The Mean ◽  
Drift Force ◽  
Low Speeds ◽  
Drift Forces

In this study, we analyze the experimental results of the mean sway (side drift) forces of six full type ships at low speeds in regular waves of various directions and compare them with numerical results of the in-house 3D panel code NEWDRIFT. It is noted that the mean sway force is most significant in relatively short waves, with the peak being observed at λ/LPP ≈ 0.5–0.6. For λ/LPP > 1.0, the corresponding value is rather small. We also observe a solid recurring pattern of the mean sway force acting on the analyzed full type ships. On this basis, we proceed to approximate the mean sway force with an empirical formula, in which only the main ship particulars and wave parameters are used. Preliminary validation results show that the developed empirical formula, which is readily applicable in practice, can accurately predict the mean sway force acting on a full ship, at both zero and non-zero speeds.

scholarly journals Evaluation of the Hydraulic Performance of a Rear-Parapet Vertical Breakwater under Regular Waves through Hydraulic Experiments

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2428 ◽  
Author(s):  
Byeong Wook Lee ◽  
Woo-Sun Park
Keyword(s):  
Climate Change ◽  
Performance Evaluation ◽  
Storm Surges ◽  
Wave Force ◽  
Hydraulic Performance ◽  
Regular Waves ◽  
Pressure Transducers ◽  
Vertical Breakwater ◽  
The Stability ◽  
Impulsive Pressure

Climate change has resulted in increased intensity and frequency of typhoons and storm surges. Accordingly, attention has been paid to securing the breakwater’s stability to protect the safety of the port. Herein, hydraulic model experiments were conducted to evaluate the hydraulic performance of a vertical breakwater having a rear parapet. For comparison, cases in which the parapet was placed on the seaside, the harborside, and at the center of the breakwater were considered. Regular waves were used for convenient performance analysis. Five wave gauges and nine pressure transducers were installed to secure physical data for hydraulic performance evaluation. Results showed that a rear parapet can reduce the maximum wave force acting on the breakwater. Even though impulsive pressure was generated, it did not affect the stability of the breakwater owing to the phase difference between the maximum wave pressures acting on the caisson and parapet. By decreasing the maximum wave force, the required self-weight that satisfies the safety factor of 1.2 was reduced by up to 82.7%; the maximum bearing pressure was reduced by up to 47.6% compared with that of the parapet located on the seaside. Thus, the rear parapet was found to be more suitable for actual applications.

Benchmark Tests of Two Body Interaction in Waves

2017 ◽  
Author(s):  
Wei Qiu ◽  
Jean-Marc Rousset ◽  
Heather Peng ◽  
Wei Meng ◽  
Boris Horel
Keyword(s):  
Numerical Solutions ◽  
Ocean Engineering ◽  
Regular Waves ◽  
Towing Tank ◽  
Benchmark Data ◽  
Benchmark Tests ◽  
Wave Basin ◽  
Close Proximity ◽  
Two Bodies ◽  
Drift Forces

As part of the test campaign led by the 27th ITTC Ocean Engineering Committee to produce reliable experimental benchmark data for multiple-body interactions in waves, model tests of two identical models in close proximity were carried out at the towing tank of Memorial University, Canada and at the wave basin of Ecole Centrale de Nantes, France. This paper presents the experimental results for the two bodies in regular waves with various gaps. The experimental data, including motions of two bodies, wave elevations in the gap and drift forces, were compared with numerical solutions based on the potential-flow solution.

scholarly journals Hydrodynamic Responses of a 6 MW Spar-Type Floating Offshore Wind Turbine in Regular Waves and Uniform Current

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 187
Author(s):  
Zhiping Zheng ◽  
Jikang Chen ◽  
Hui Liang ◽  
Yongsheng Zhao ◽  
Yanlin Shao
Keyword(s):  
Perturbation Method ◽  
Time Domain ◽  
Strong Influence ◽  
Offshore Wind ◽  
Regular Waves ◽  
Wave Drift ◽  
Uniform Current ◽  
The Time Domain ◽  
Wave Drift Forces ◽  
Drift Forces

In order to improve the understanding of hydrodynamic performances of spar-type Floating Offshore Wind Turbines (FOWTs), in particular the effect of wave-current-structure interaction, a moored 6MW spar-type FOWT in regular waves and uniform current is considered. The wind loads are not considered at this stage. We apply the potential-flow theory and perturbation method to solve the weakly-nonlinear problem up to the second order. Unlike the conventional formulations in the inertial frame of reference, which involve higher derivatives on the body surface, the present method based on the perturbation method in the non-inertial body-fixed coordinate system can potentially avoid theoretical inconsistency at sharp edges and associated numerical difficulties. A cubic Boundary Element Method (BEM) is employed to solve the resulting boundary-value problems (BVPs) in the time domain. The convective terms in the free-surface conditions are dealt with using a newly developed conditionally stable explicit scheme, which is an approximation of the implicit Crank–Nicolson scheme. The numerical model is firstly verified against three reference cases, where benchmark results are available, showing excellent agreement. Numerical results are also compared with a recent model test, with a fairly good agreement though differences are witnessed. Drag loads based on Morison’s equation and relative velocities are also applied to quantify the influence of the viscous loads. To account for nonlinear restoring forces from the mooring system, a catenary line model is implemented and coupled with the time-domain hydrodynamic solver. For the considered spar-type FOWT in regular-wave and current conditions, the current has non-negligible effects on the motions at low frequencies, and a strong influence on the mean wave-drift forces. The second-order sum-frequency responses are found to be negligibly small compared with their corresponding linear components. The viscous drag loads do not show a strong influence on the motions responses, while their contribution to the wave-drift forces being notable, which increases with increasing wave steepness.

Drift of an articulated cylinder in regular waves

1984 ◽  
Vol 394 (1807) ◽  
pp. 363-385 ◽  
Keyword(s):  
Near Field ◽  
Second Order ◽  
Regular Waves ◽  
Floating Bodies ◽  
Wave Heights ◽  
Tilt Mode ◽  
The Mean ◽  
Wave Induced ◽  
Theoretical Results ◽  
Drift Forces

Potential flow theory is used to investigate the wave induced harmonic response and the mean drift of an articulated column in regular waves. The mean drift horizontal force is evaluated by means of the Stokes expansion to second order in wave steepness. Analyses based on both near field and far field formulations are shown to give identical expressions, provided that the second-order forces at the intersection between column and seabed are included in the near field approach. The latter have not been considered in previous studies concerned with drift forces on floating bodies. It is shown that the drift forces on a column, although of second order, can excite piech responses of first order: this is because articulated columns are designed to have a low natural frequency in the tilt mode, relative to wave frequencies. Comparison of the theoretical results with experimental data, from a model tested in regular waves, suggests reasonable agreement for the drift forces over a range of frequencies and two wave heights.

Hydrodynamic interaction between two barges during berthing operation in regular waves

2015 ◽  
Vol 106 ◽  
pp. 317-328 ◽  
Author(s):  
Bo Woo Nam ◽  
Yonghwan Kim ◽  
Sa Young Hong
Keyword(s):  
Hydrodynamic Interaction ◽  
Regular Waves

On Three-Dimensional Solutions of Drift Forces and Moments Between Two Ships in Waves

2002 ◽  
Vol 46 (04) ◽  
pp. 280-288
Author(s):  
Ming-Chung Fang ◽  
Gung-Rong Chen
Keyword(s):  
Numerical Solutions ◽  
Three Dimensional ◽  
Source Distribution ◽  
Regular Waves ◽  
Lateral Drift ◽  
Expansion Technique ◽  
Present Technique ◽  
Principal Value ◽  
Incident Waves ◽  
Drift Forces

A far-held approach solving the lateral drift forces and moments between two ships in regular waves is adopted. The velocity potentials for diffraction and radiation based on a 3-D-source distribution technique are obtained. Using the Telste & Noblesse algorithm with a series expansion technique for the principal value integral solves the numerical solutions for corresponding Green functions and their derivatives. One pair of ship models is used for numerical calculations and a 2-D method based on the near-held approach is also included for comparisons. Generally the results obtained by the present technique indicate that the interaction effects between two ships have a profound influence on the drift forces and moments, and the direction of incident waves plays an important role. The results also show that the values predicted by the 2-D method are always very much overestimated because of the trapping energy between two ships. Therefore, the 3-D method prediction model developed here is regarded as more physically reasonable than the 2-D one.

A Hybrid Method for Predicting Ship Maneuverability in Regular Waves

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Tianlong Mei ◽  
Yi Liu ◽  
Manasés Tello Ruiz ◽  
Evert Lataire ◽  
Marc Vantorre ◽  
...  
Keyword(s):  
Hybrid Method ◽  
Panel Method ◽  
Regular Waves ◽  
Ship Maneuvering ◽  
Wave Drift ◽  
Hydrodynamic Derivatives ◽  
Ship Maneuverability ◽  
Wave Drift Forces ◽  
Maneuvering Motion ◽  
Drift Forces

Abstract Traditionally, ship maneuvering is analyzed under calm water condition. In a more realistic scenario, such as a ship sailing in waves, the importance of taking the wave effects into account should be stressed. In this context, this paper proposes a hybrid method for predicting ship maneuverability in regular waves by combining a potential flow theory based panel method and a Reynolds-averaged Navier–Stokes (RANS)-based computational fluid dynamics method. The mean wave drift forces are evaluated by applying a three-dimensional time-domain higher-order Rankine panel method, which takes the effects of ship's forward speed and lateral speed into consideration. The hull-related hydrodynamic derivatives in the equations of ship maneuvering motion are determined by using a RANS solver based on the double-body model. Then, the two-time scale method is applied to predict ship maneuvering in regular waves by integrating the seakeeping model in a three degrees-of-freedom MMG model for ship maneuvering motion. The numerical results of a laterally drifting S175 container ship, including the wave-induced motions, wave drift forces, and turning trajectories in regular waves, are presented and compared with the available experimental data in literature. The results show that the proposed hybrid method can be used for qualitatively predicting ship maneuvering behavior in regular waves.

Sign in / Sign up

Export Citation Format

Share Document