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.

Numerical Evaluation of Ship Maneuvering Performance in Waves

2018 ◽  
Author(s):  
Min-Guk Seo ◽  
Bo Woo Nam ◽  
Yeon-gyu Kim
Keyword(s):  
Irregular Waves ◽  
Time Signal ◽  
Regular Waves ◽  
Ship Maneuvering ◽  
Wave Drift ◽  
Mmg Model ◽  
Free Running ◽  
Drift Force ◽  
Wave Drift Forces ◽  
Drift Forces

This paper considers a numerical computation of ship maneuvering performance in waves. For this purpose, modular-type maneuvering model (MMG model) is adopted and wave drift forces and moments are included in maneuvering equation of motion. Wave drift forces ware calculated using a seakeeping program based on higher-order Rankine panel method. When calculating the wave drift force acting on a ship, the forward speed, wave heading, wave period and drift angle of the ship are considered as key parameters. It means that ship’s lateral speed is also included to calculate wave drift force. Numerical simulations are carried out in regular waves using S175 containership and computation results are validated by comparing them with results of free-running model test. Using the developed program, numerical simulation in irregular waves are, also, conducted and discussion is made on the sensitivities of time signal of wave elevation on turning performance.

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.

Wave Drift Forces' Calculation on Two Floating Bodies Based on the Boundary Element Method—Attempt for Improvement of the Constant Panel Method

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Qiao Li ◽  
Yasunori Nihei
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Evaluation Method ◽  
Panel Method ◽  
Floating Bodies ◽  
Wave Drift ◽  
Wave Drift Forces ◽  
Multiple Floating Bodies ◽  
Drift Forces ◽  
Element Method

An improved constant panel method for more accurate evaluation of wave drift forces and moment is proposed. The boundary element method (BEM) of solving boundary integral equations is used to calculate velocity potentials of floating bodies. The equations are discretized by either the higher-order boundary element method or the constant panel method. Though calculating the velocity potential via the constant panel method is simple, the results are unable to accurately evaluate wave drift forces and moment. An improved constant panel method is introduced to address these issues. The improved constant panel method can, without difficulty, employ the near-field method to evaluate wave drift forces and moment, especially for multiple floating bodies. Results of the new evaluation method will be compared with other evaluation method. Additionally, hydrodynamic interaction between multiple floating bodies will be assessed.

A Study on the Wave Drift Forces Calculation on Two Floating Bodies Based on the Boundary Element Method: Attempt for Improvement of the Constant Panel Method

2016 ◽  
Author(s):  
Qiao Li ◽  
Takashi Tsubogo ◽  
Yoshiho Ikeda ◽  
Yasunori Nihei
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Velocity Potential ◽  
Near Field ◽  
Field Method ◽  
Panel Method ◽  
Floating Bodies ◽  
Wave Drift ◽  
Wave Drift Forces ◽  
Drift Forces

The boundary element method (BEM) which can solve the boundary integral equations is used to calculate the velocity potential on the floating bodies. The equation is discretized by the higher order BEM or the constant panel method. The constant panel method is relatively easy to compute the velocity potential. However the near field method cannot evaluate the wave drift forces and moment accurately, when the velocity potential is computed by the constant panel method. In the article, a new numerical technic of the constant panel method is proposed. Then it is easy to take advantage of the near field method to calculate the wave drift forces and moment, especially considering two floating system. In addition, the results of the fluid forces calculated by new method are compared to the other methods results. At last the hydrodynamic interaction between two floating bodies is assessed in the calculation of the wave exciting forces and the wave drift forces.

Time-Domain Hydrodynamic Model for Mooring Analysis of a Spread Moored Fpso With Calibration of Wave Drift Forces

2021 ◽  
Author(s):  
Min Zhang ◽  
Junrong Wang ◽  
Junfeng Du ◽  
Nuno Miguel Magalhaes Duque Da Fonseca ◽  
Galin Tahchiev ◽  
...  
Keyword(s):  
Time Domain ◽  
Hydrodynamic Model ◽  
Wave Drift ◽  
Wave Drift Forces ◽  
Drift Forces

A Nonlinear Mathematical Model for Ship Turning Circle Simulation in Waves

2005 ◽  
Vol 49 (02) ◽  
pp. 69-79 ◽  
Author(s):  
Ming-Chung Fang ◽  
Jhih-Hong Luo ◽  
Ming-Ling Lee
Keyword(s):  
Mathematical Model ◽  
Degrees Of Freedom ◽  
Regular Waves ◽  
Nonlinear Mathematical Model ◽  
Ship Maneuvering ◽  
Sea Trial ◽  
Six Degrees Of Freedom ◽  
Strip Theory ◽  
Calm Water ◽  
Maneuvering Motion

In the paper, a simplified six degrees of freedom mathematical model encompassing calm water maneuvering and traditional seakeeping theories is developed to simulate the ship turning circle test in regular waves. A coordinate system called the horizontal body axes system is used to present equations of maneuvering motion in waves. All corresponding hydrodynamic forces and coefficients for seakeeping are time varying and calculated by strip theory. For simplification, the added mass and damping coefficients are calculated using the constant draft but vary with encounter frequency. The nonlinear mathematical model developed here is successful in simulating the turning circle of a containership in sea trial conditions and can be extended to make the further simulation for the ship maneuvering under control in waves. Manuscript received at SNAME headquarters February 19, 2003; revised manuscript received January 27, 2004.

On Approximations of the Wave Drift Forces Acting on Semi-Submersible Platforms With Heave Plates

2016 ◽  
Author(s):  
Bernard Molin ◽  
Jean-Baptiste Lacaze
Keyword(s):  
Wave Field ◽  
Scattered Wave ◽  
Diffraction Radiation ◽  
Morison Equation ◽  
Wave Drift ◽  
Horizontal Wave ◽  
Heave Plate ◽  
Drift Force ◽  
Wave Drift Forces ◽  
Drift Forces

The horizontal wave drift force acting on a vertical floating column, without then with a heave plate, is considered. Computations are performed with a diffraction-radiation code and through the Morison and Rainey equations. Focus is on wave frequencies around the heave resonance where the drift force may be significant, even though the scattered wave-field being weak. It is found that the Morison equation overpredicts the drift force while Rainey equations perform rather well.

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