Wave-Induced Motions of Multiple Floating Bodies

This paper describes the development and implementation of a reduced-order model to represent the hydrodynamic forces acting on a ship using Impulse-Response Functions (IRF). The approach will be conducted using Aegir, a timedomain seakeeping program that uses an advanced, Non-Rational Uniform B-Spline (NURBS) based, high-order boundary element method. The Cummins equation is slightly modified such that the memory function is decomposed into two terms: one for the impulsive velocity and the other term for the impulsive displacement. The present approach also further develops a method to simulate interactions between multiple floating bodies. The IRF convolutions for the free surface memory effect significantly reduce the computational effort compared to direct simulation. This will be demonstrated for both single and multi-body forward-speed, seakeeping simulations.

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Yaw Drift Moment of a Floating Structure in Waves

24th International Conference on Offshore Mechanics and Arctic Engineering: Volume 2 ◽

10.1115/omae2005-67462 ◽

2005 ◽

Cited By ~ 1

Author(s):

Dimitris Spanos ◽

Apostolos Papanikolaou

Keyword(s):

Hydrodynamic Forces ◽

Computational Method ◽

Irregular Waves ◽

Linear Potential ◽

Floating Bodies ◽

Floating Structure ◽

Natural Wave ◽

Positioning Systems ◽

Floating Structures ◽

Wave Induced

The wave induced yaw drift moment on floating structures is of particular interest when the lateral yaw motion of the structure should be controlled by moorings and/or active dynamic positioning systems. In the present paper, the estimation of the yaw drift moment in the modeled natural wave environment is conducted by application of a nonlinear time domain numerical method accounting for the motion of arbitrarily shaped floating bodies in waves. The computational method is based on linear potential theory and includes the non-linear hydrostatic terms in an exact way, whereas the higher-order wave-induced effects are partly approximated. Despite the approximate modeling of the second order hydrodynamic forces, the method proved to satisfactorily approach the dominant part of the exerted hydrodynamic forces enabling the calculation of drift forces and of other drift effects in irregular waves. Hence, the subject yaw drift moment in the modeled natural wave environment is derived, resulting to a basic reference for the design of similar type floating structures.

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Wave-Induced Motions of Floating Bodies

Ocean Engineering Mechanics ◽

10.1017/cbo9780511812309.013 ◽

2012 ◽

pp. 376-452

Author(s):

Michael E. McCormick

Keyword(s):

Floating Bodies ◽

Wave Induced

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Wave forces on multiple floating bodies

Applied Ocean Research ◽

10.1016/s0141-1187(82)80015-1 ◽

1982 ◽

Vol 4 (1) ◽

pp. 2-8 ◽

Cited By ~ 3

Author(s):

Akira Masumoto ◽

Yoshio Yamagami ◽

Ryuji Sakata

Keyword(s):

Wave Forces ◽

Floating Bodies ◽

Multiple Floating Bodies

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

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4042180 ◽

2019 ◽

Vol 141 (4) ◽

Cited By ~ 1

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.

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Drift of an articulated cylinder in regular waves

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1984.0084 ◽

1984 ◽

Vol 394 (1807) ◽

pp. 363-385 ◽

Cited By ~ 6

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.

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