Influence of second-order wave force and focusing position on dynamic responses of tension leg platform under a freak wave

2014 ◽

Cited By ~ 5

Author(s):

Erin E. Bachynski ◽

Torgeir Moan

Keyword(s):

Fatigue Damage ◽

Wind Turbines ◽

Maximum Stress ◽

Wave Force ◽

Second Order ◽

Tension Leg Platform ◽

Operational Conditions ◽

Sum Frequency ◽

Wave Conditions ◽

Maximum Stresses

Although the majority of studies of tension leg platform wind turbines (TLPWTs) have focused on aligned wind and wave conditions, it is not uncommon for the wind and waves to be significantly misaligned. Wind-wave misalignment is expected to influence both ultimate and fatigue loads. The present work compares the dynamic response of a representative TLPWT in both aligned and misaligned wind and wave conditions, with and without second order sum-frequency potential forces. The contribution of the second order loads to the maximum stress and to the short-term fatigue damage at the tower base, tower top, and tendon fairleads is examined for several operational conditions. The same TLPWT with softened tendons is also studied in order to examine the sensitivity of the results to the system natural frequencies. The fatigue damage decreased in misaligned wind and wave conditions, but the effect of second order forces increased. For the soft TLPWT design, second order forces had an important effect on fatigue in both aligned and misaligned conditions. Despite the increase in side-side loading in misaligned conditions, aligned conditions were associated with larger maximum stresses (in operational conditions).

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Second-Order Low-Frequency Wave Forces on a SPM Offloading Tanker in Shallow Water

Volume 1: Offshore Technology ◽

10.1115/omae2008-58048 ◽

2008 ◽

Author(s):

S. Ma ◽

S. Shi ◽

M. H. Kim

Keyword(s):

Shallow Water ◽

Transfer Functions ◽

Low Frequency ◽

Wave Force ◽

Second Order ◽

Dynamic Responses ◽

Mooring Line ◽

Wave Forces ◽

Frequency Wave ◽

The Impact

This paper studies the influence of three different calculation methods of the second-order low-frequency (LF) wave forces on the tanker responses and hawser/mooring tensions in relatively shallow water region. The vessel-mooring-riser coupled dynamic analysis computer program HARP is used to simulate the coupled dynamic responses of offloading tanker moored to a SPM (Single Point Mooring). Because the SPM is supposed to be deployed in shallow water and the slowly varying drift motions of the tanker are to dominate the motion responses in typical operational conditions, the accurate calculation of LF wave-force quadratic transfer functions (QTFs) becomes important especially for mooring and hawser tensions. Like common practice, the so-called Newman’s approximation and another approximation method without including complicated free-surface integrals are first used to calculate the LF QTFs on the offloading tanker and they are compared with the complete QTF results. Further comparison is performed by calculating the resulting LF wave-force spectra and response time series by using the three different methods. The impact of the three different approaches on vessel surge motions and hawser/mooring line tensions is also addressed.

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Sensory processing in a thermal afferent pathway

Journal of Neurophysiology ◽

10.1152/jn.1985.53.2.429 ◽

1985 ◽

Vol 53 (2) ◽

pp. 429-434 ◽

Cited By ~ 20

Author(s):

S. N. Davies ◽

G. E. Goldsmith ◽

R. F. Hellon ◽

D. Mitchell

Keyword(s):

Sensory Processing ◽

Receptive Fields ◽

Second Order ◽

Dynamic Responses ◽

Trigeminal Nucleus ◽

Afferent Pathway ◽

Afferent Fibers ◽

Level Of Activity ◽

Caudal Trigeminal Nucleus ◽

High Level

Extracellular recordings were made from cold-receptive afferent fibers in the trigeminal ganglion of rats anesthetized with halothane. By applying a standardized series of steady or changing temperatures to the receptive fields, we recorded the static and dynamic responses of the afferents. Comparable recordings were made from neurons in the marginal layer of the caudal trigeminal nucleus onto which the cold fibers synapse. The static and dynamic responses of the afferent fibers were reproduced faithfully by the second-order neurons, but at a much higher level of activity. Ganglionectomy silenced the second-order cells. Their continuous high level of activity appears to depend on the tonic input from the afferent fibers and not on any intrinsic circuits in the medulla.

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Second-Order Diffraction Loads on Plural Vertical Cylinder With Arbitrary Cross Sections

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.3257026 ◽

1987 ◽

Vol 109 (4) ◽

pp. 314-319

Author(s):

K. Masuda ◽

W. Kato ◽

H. Ishizuka

Keyword(s):

Boundary Value Problem ◽

Cross Sections ◽

Present Method ◽

Boundary Value ◽

Vertical Cylinder ◽

Wave Force ◽

Second Order ◽

Wave Forces ◽

Order Diffraction ◽

Rectangular Cylinders

The purpose of the present study is development of a powerful numerical method for calculating second-order diffraction loads on plural vertical cylinder with arbitrary cross sections. According to the present method, second-order wave force can be obtained from a linear radiation potential without solving second-order boundary value problem. The boundary value problem for the radiation potential is solved with the hybrid boundary element method. The computations for circular and rectangular cylinders were carried out and compared with the experiments. In addition, second-order wave forces on twin circular cylinder are calculated with the present method.

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Erratum for “Second-Order Wave Force on Large Vertical Cylinder”

Journal of the Waterway, Port, Coastal and Ocean Division ◽

10.1061/jwpcdx.0000043 ◽

1977 ◽

Vol 103 (3) ◽

pp. 388-389

Author(s):

Subrata K. Chakrabarti

Keyword(s):

Vertical Cylinder ◽

Wave Force ◽

Second Order

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Second-Order Biharmonic Response of a Tension-Leg Platform

Journal of the Society of Naval Architects of Japan ◽

10.2534/jjasnaoe1968.1991.151 ◽

1991 ◽

Vol 1991 (169) ◽

pp. 151-164

Author(s):

Tetsuya Matsui ◽

Yuhji Sakoh

Keyword(s):

Second Order ◽

Tension Leg Platform

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Second-Order Perturbation Analysis of In-Plane Blade-Hub Dynamics of Horizontal-Axis Wind Turbines

Volume 8: 30th Conference on Mechanical Vibration and Noise ◽

10.1115/detc2018-86203 ◽

2018 ◽

Author(s):

Ayse Sapmaz ◽

Brian F. Feeny

Keyword(s):

Perturbation Analysis ◽

Multiple Scales ◽

Perturbation Expansion ◽

Second Order ◽

Horizontal Axis ◽

Dynamic Responses ◽

Order Perturbation ◽

Resonance Case ◽

Horizontal Axis Wind Turbine ◽

Rotor Angle

This paper deals with a second-order perturbation analysis of the in-plane dynamic responses of both tuned and mistuned three-blade-hub horizontal-axis wind-turbine equations. The blades are under effect of gravitational and cyclic aerodynamics forces and centrifugal forces. Although the blades and hub equations are coupled, they can be decoupled by changing the independent variable from time to rotor angle and by using a small parameter approximation. A second-order method of multiple scales is applied in the rotor-angle domain to analyze in-plane blade-hub dynamics. A superharmonic resonance case at one third the natural frequency was revealed. This resonance case was not captured by a first-order perturbation expansion. The relationship between response amplitude and frequency is studied. The effect of blade mistuning on the coupled blade-hub dynamics are taken into account.

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

29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 4 ◽

10.1115/omae2010-20618 ◽

2010 ◽

Cited By ~ 2

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.

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