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.

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.

Wave Drift Forces on Three Barges Arranged Side by Side in Floatover Installation

2013 ◽  
Author(s):  
Xin Xu ◽  
Jianmin Yang ◽  
Xin Li ◽  
Haining Lu
Keyword(s):  
Near Field ◽  
Field Method ◽  
Hydrodynamic Interactions ◽  
Body System ◽  
Wave Drift ◽  
Single Body ◽  
Motion Responses ◽  
Wave Drift Forces ◽  
Multi Body ◽  
Drift Forces

Floatover is a new method for installing integrated topside of a spar platform. It has several obvious advantages such as less time and cost compared with derrick lifting. In general, the floatover installation consists of three procedures: firstly a single barge is used for long-distance transportation of the topside in order to get good stability; secondly two barges take place of the single barge for floatover installation near the operating site; finally the topside is transferred from the two barges to the spar hull and the installation is completed. Between the first and second procedures, the case occurs that the single transportation barge is sided left and right by two floatover barges in the second procedure with close proximity. This case is concerned by many designers and operators for the security problem brought by possible large relative motions and forces of the three barges in side by side configuration. The hydrodynamics of side-by-side barges are much more complex than that of a single barge in waves. In numerical simulation, it is a challenge to consider all effects including the hydrodynamic interactions, the shielding effects, the viscous effects and the wave resonance effect which has been observed in the gaps between the barges and has a significant impact on wave drift forces. In this paper, motion responses and wave drift forces were calculated in frequency domain for both the multi-body system and the single body. Far-field, middle-field and near-field method were all carried out to calculate wave drift forces. Numerical analysis was executed using potential flow code WAMIT. Corresponding model tests were also performed in the Deepwater Offshore Basin in Shanghai Jiao Tong University. Comparison between numerical and experimental results shows that numerical results agree well with the experiment and that middle-field method has better convergence than near-field method. The comparison between the multi-body system and single body shows that the hydrodynamic interactions (including wave shielding effect and Helmholtz resonance of water in the gaps) are remarkable and motion responses in the multi-body system are larger than single barge at some frequencies.

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.

scholarly journals Near-Trapping on a Four-Column Structure and the Reduction of Wave Drift Forces Using Optimized Method

2020 ◽  
Vol 8 (3) ◽  
pp. 174 ◽  
Author(s):  
Guanghua He ◽  
Zhigang Zhang ◽  
Wei Wang ◽  
Zhengke Wang ◽  
Penglin Jing
Keyword(s):  
Numerical Model ◽  
Floating Bodies ◽  
Large Wave ◽  
Approach Angle ◽  
Wave Approach ◽  
Wave Drift ◽  
Column Structure ◽  
Wave Drift Forces ◽  
Drift Forces ◽  
Wave Elevations

The near-trapping phenomenon, which can lead to high wave elevations and large wave drift forces, is investigated by a floating four-column structure. To solve this wave-structure interaction problem, a numerical model is established by combining the wave interaction theory with a higher-order boundary element method. Based on this numerical model, behaviors of scattered waves at near-trapping conditions are studied; and the superposition principle of free-surface waves is introduced to understand this near-trapping phenomenon. To avoid the near-trapping phenomenon and protect the structure, a way for rotating the structure to change the wave-approach angle is adopted, and improvements of the wave elevations around the structure and the wave drift forces acting on each column are found. Moreover, a genetic-algorithm-based optimization method is adopted in order to minimize the total wave drift force acting on the whole structure at various wavenumbers by controlling the draft of floating bodies, the wave-approach angle and the separation distance between adjacent floating bodies. With the final optimized parameters, the wave drift forces both on each column and on the whole structure can be significantly reduced. The optimized arrangement obtained from a certain wavenumber can work not only at this target wavenumber but also at a range of wavenumbers.

Wave Drift Forces in Directional Seas in Shallow Water

2009 ◽  
Author(s):  
J. A. Pinkster
Keyword(s):  
Shallow Water ◽  
Near Field ◽  
Low Frequency ◽  
Computational Method ◽  
Direct Evaluation ◽  
Beam Seas ◽  
Wave Drift ◽  
Wave Effects ◽  
Wave Drift Forces ◽  
Drift Forces

Wave drift forces in shallow water are dominated by low frequency bound wave effects. The effect of short-crestedness of the waves on the wave drift forces is investigated based on direct evaluation of the near field pressure equations in irregular directional seas. The background to the method is treated and examples of results showing some of the details of the computational method are given. Some trends found for the effect of the short-crestedness on the second order wave drift forces on a typical LNG carrier moored in shallow water are presented. Finally, results are given of low-frequency horizontal motions of the LNG carrier in directionally spread head, bow-quartering and beam seas for a range of directional spreading values.

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
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