Mooring Dynamics Phenomena Due to Slowly-Varying Wave Drift

2002 ◽  
Author(s):  
Michael M. Bernitsas ◽  
Joa˜o Paulo J. Matsuura ◽  
Torgrim Andersen
Keyword(s):  
Dynamic Responses ◽  
Resonance Phenomenon ◽  
University Of Michigan ◽  
Wave Drift ◽  
Mooring Dynamics ◽  
Wave Drift Forces ◽  
The University ◽  
New Phenomena ◽  
External Time ◽  
Drift Forces

The effects of slowly-varying wave drift forces on the nonlinear dynamics of mooring systems have been studied extensively in the past 30 years. It has been concluded that slowly-varying wave drift may resonate with mooring system natural frequencies. In recent work, we have shown that this resonance phenomenon is only one of several possible nonlinear dynamic responses of mooring systems to slowly-varying wave drift excitation. We were able to reveal new phenomena based on the design methodology developed at the University of Michigan for autonomous mooring systems and treating slowly-varying drift as an external time-varying force. In this paper, the U of M methodology is used systematically to reveal seven phenomena induced by mean and slowly-varying drift forces; one of those is resonance. Conceptually, numerous qualitatively different behaviors may be induced. The next step towards comprehensive identification of such phenomena is taken by introducing the method of harmonic balance to study nonautonomous mooring systems.

Mooring Dynamics Phenomena Due to Slowly-Varying Wave Drift

2004 ◽  
Vol 126 (4) ◽  
pp. 280-286 ◽  
Author(s):  
Michael M. Bernitsas ◽  
Joa˜o Paulo J. Matsuura ◽  
Torgrim Andersen
Keyword(s):  
Dynamic Responses ◽  
Resonance Phenomenon ◽  
University Of Michigan ◽  
Wave Drift ◽  
Mooring Dynamics ◽  
Wave Drift Forces ◽  
The University ◽  
New Phenomena ◽  
External Time ◽  
Drift Forces

The effects of slowly varying wave drift forces on the nonlinear dynamics of mooring systems have been studied extensively in the past 30 years. It has been concluded that slowly varying wave drift may resonate with mooring system natural frequencies. In recent work, we have shown that this resonance phenomenon is only one of several possible nonlinear dynamic responses of mooring systems to slowly varying wave drift excitation. We were able to reveal new phenomena based on the design methodology developed at the University of Michigan for autonomous mooring systems and treating slowly varying drift as an external time-varying force. In this paper, the U of M methodology is used systematically to reveal seven phenomena induced by mean and slowly varying drift forces; one of those is resonance. Conceptually, numerous qualitatively different behaviors may be induced. The next step toward the comprehensive identification of such phenomena is taken by introducing the method of harmonic balance to study nonautonomous mooring systems.

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

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.

Real Time Prediction of Second Order Wave Drift Forces for Wave Force Feed Forward in DP

2010 ◽  
Author(s):  
P. Naaijen ◽  
R. H. M. Huijsmans
Keyword(s):  
Wave Field ◽  
Prediction Error ◽  
Wave Force ◽  
Second Order ◽  
First Order ◽  
Wave Drift ◽  
Wave Elevation ◽  
X Band ◽  
Wave Drift Forces ◽  
Drift Forces

The presented research is an extension of the development of an onboard wave and motion estimation system that aims to predict wave elevation and wave frequent vessel motions some 60–120 s ahead, using remote measurements of short crested waves. The main aim is to provide decision support during motion critical offshore operations. As an addition to this, an attempt is made to predict second order wave drift forces. This can be useful for condition monitoring of a Dynamic Positioning (DP) system [18] or for feed forward of wave drift forces into the control of DP systems. The paper describes the techniques used to predict second order wave drift forces real time from remote wave measurements. For validation, measurement data is used from model experiments during which wave elevation in irregular short crested seas was recorded by a large number of probes simultaneously. A method is described to obtain a 3D representation of a wave field in such a way that it can be used to predict both first order waves and motions and second order forces. The second order forces resulting from the wave field description as obtained from remote probe measurements can be compared to those that have been derived from the probes in the proximity of the prediction location, thus providing insight in the sensitivity of the 2nd order wave force prediction error with respect to the first order wave prediction error. In a full scale field situation, remote wave sensing can be provided by X-band radar. Possibilities for application of the developed method with the WAMOS II X-band radar system is considered.

Sign in / Sign up

Export Citation Format

Share Document