The UK Christchurch Bay Compliant Cylinder Project: analysis and interpretation of Morison wave force and response data

Najafian, G.; Tickell, R.G.; Burrows, Roger; Bishop, John

doi:10.1016/s0141-1187(00)00009-2

Cited by 14 publications

(15 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For random wave fields used in fatigue calculations, the design rules advise, for a vertical cylinder following coefficients, C m D 2.0 and C d D 0.65. 17 The Christchurch Bay experiments, 18 which seem of particular relevance because they deal with random waves, concluded that for inertia-dominated load cases, the inertia coefficient approaches the value of 2.0. The drag coefficient could not be determined so accurately, but at least common values of C d D 0.65 to 1.05 are not contradicted.…”

Section: Hydrodynamic Modelmentioning

confidence: 99%

The dynamics of an offshore wind turbine in parked conditions: a comparison between simulations and measurements

et al. 2014

View full text Add to dashboard Cite

Offshore wind turbines are complex structures, and their dynamics can vary significantly because of changes in operating conditions, e.g., rotor-speed, pitch angle or changes in the ambient conditions, e.g., wind speed, wave height or wave period. Especially in parked conditions, with reduced aerodynamic damping forces, the response due to wave actions with wave frequencies close to the first structural resonance frequencies can be high. Therefore, this paper will present numerical simulations using the HAWC2 code to study an offshore wind turbine in parked conditions. The model has been created according to best practice and current standards based on the design of an existing Vestas V90 offshore wind turbine on a monopile foundation in the Belgian North Sea. The damping value of the model's first fore-aft mode has been tuned on the basis of measurements obtained from a long-term ambient monitoring campaign on the same wind turbine. Using the updated model of the offshore wind turbine, the paper will present some of the effects of the different design parameters and the different ambient conditions on the dynamics of an offshore wind turbine. The results from the simulations will be compared with the processed data obtained from the real measurements. The accuracy of the model will be discussed in terms of resonance frequencies, mode shapes, damping value and acceleration levels, and the limitations of the simulations in modeling of an offshore wind turbine will be addressed.

show abstract

Section: Hydrodynamic Modelmentioning

confidence: 99%

The dynamics of an offshore wind turbine in parked conditions: a comparison between simulations and measurements

et al. 2014

View full text Add to dashboard Cite

show abstract

“…Stavros [28] investigated the use of Morisons equation in estimating the response of an offshore structural model and concluded that amplified equivalent damping factors should be used on the results from the linearized displacement to match the nonlinear response. Other researchers [2,29,30,31] who studied the wave induced forces derived from the linear form of Morisons equation. But only the latter has studied the validity and accuracy of the linear form of Morisons in estimating the wave induced forces as compared to non linear form.…”

Section: Hydrodynamic Forcesmentioning

confidence: 99%

Design of a Test Rig for Vibration Control of Oil Platforms Using Magneto-Rheological Dampers

Karkoub

Lamont

Chaar

2011

Journal of Offshore Mechanics and Arctic Engineering

View full text Add to dashboard Cite

Offshore steel structures are widely used around the world, e.g., in Gulf of Mexico, the Middle East, and the North Sea. These structures are costly to build, and any damage to them could be catastrophic financially and environmentally. There are many factors that could possibly affect the health of these steel structures, particularly hydrodynamic forces. These forces cause the structure to vibrate and in the long run could lead to fatigue failure. Therefore, measures have to be taken in order to prevent these structures from failing. Magneto-rheological (MR) dampers are proven as a feasible alternative to reducing structural vibrations. An experimental setup is built in our laboratory to improve the dynamic modeling of steel jacketlike structures and study the effectiveness of MR dampers in decreasing the hydrodynamically induced vibrations. The structure is analyzed theoretically and experimentally, and the results are presented here.

show abstract

“…Marine growth will give a reduction of C m , though it must never be less than 1·8. The Christchurch Bay experiments, 17 which seem of particular relevance because they deal with random waves, concluded that for inertia-dominated load cases the inertia coefficient approaches the value of 2·0. The drag coefficient could not be determined so accurately, but at least common values of C d = 0·65-1·05 are not contradicted.…”

Section: Coefficients For Morison's Equationmentioning

confidence: 99%

“…The wavenumber k d is found with the dispersion relation for finite depth d: (17) For finite depth d the wavenumber k d must be found iteratively. If the depth is infinite, the tanh function becomes unity, the dispersion relation reduces to (18) and k • is found with (19) Using the dispersion relation again, the derivative of F can be found.…”

Section: Appendix C: Tma Correctionmentioning

confidence: 99%

See 1 more Smart Citation

Influence of wave modelling on the prediction of fatigue for offshore wind turbines

Veldkamp

Tempel

2004

Wind Energy

View full text Add to dashboard Cite

Currently it is standard practice to use Airy linear wave theory combined with Morison's formula for the calculation of fatigue loads for offshore wind turbines. However, offshore wind turbines are typically placed in relatively shallow water depths of 5-25 m where linear wave theory has limited accuracy and where ideally waves generated with the Navier-Stokes approach should be used.This article examines the differences in fatigue for some representative offshore wind turbines that are found if first-order, second-order and fully non-linear waves are used.The offshore wind turbines near Blyth are located in an area where non-linear wave effects are common.Measurements of these waves from the OWTES project are used to compare the different wave models with the real world in spectral form. Some attention is paid to whether the shape of a higher-order wave height spectrum (modified JONSWAP) corresponds to reality for other places in the North Sea, and which values for the drag and inertia coefficients should be used.

show abstract

The UK Christchurch Bay Compliant Cylinder Project: analysis and interpretation of Morison wave force and response data

Cited by 14 publications

References 4 publications

The dynamics of an offshore wind turbine in parked conditions: a comparison between simulations and measurements

The dynamics of an offshore wind turbine in parked conditions: a comparison between simulations and measurements

Design of a Test Rig for Vibration Control of Oil Platforms Using Magneto-Rheological Dampers

Influence of wave modelling on the prediction of fatigue for offshore wind turbines

Contact Info

Product

Resources

About