Wave reflection effects on small craft motions

1996 ◽  
Vol 23 (2) ◽  
pp. 340-346
Author(s):  
Michael Isaacson ◽  
John Baldwin ◽  
Andrew Kennedy
Keyword(s):  
Numerical Model ◽  
Wave Reflection ◽  
Numerical Study ◽  
Diffraction Theory ◽  
Coastal Engineering ◽  
Irregular Waves ◽  
Induced Response ◽  
Small Craft ◽  
Wave Heights ◽  
Wave Induced

This paper describes an experimental and a numerical study of the wave-induced response of a moored vessel near a reflecting wall, for the purpose of incorporating wave reflection effects into wave agitation criteria for small craft harbours. The motions of a model vessel have been measured for a range of wave heights, wave periods, wave directions, mooring conditions, and vessel locations, and with both regular and irregular waves. These have been compared with the results of a numerical model based on linear diffraction theory. An expression is developed to relate vessel motions near a partially reflecting wall to motions in unreflected waves. This has been found to agree well with the experimental results, and is used to recommend an extension to existing wave agitation criteria for small craft harbours so as to take account of the presence of reflecting walls. Key words: coastal engineering, harbours, hydrodynamics, marinas, wave agitation, waves.

Bending Moments and Shear Forces in Ships Sailing in Irregular Waves

1981 ◽  
Vol 25 (04) ◽  
pp. 243-251
Author(s):  
J. Juncher Jensen ◽  
P. Terndrup Pedersen
Keyword(s):  
Linear Part ◽  
Vertical Motion ◽  
Bending Moment ◽  
Irregular Waves ◽  
Bending Moments ◽  
Shear Forces ◽  
Strip Theory ◽  
Wave Heights ◽  
Exciting Forces ◽  
Wave Induced

This paper presents some results concerning the vertical response of two different ships sailing in regular and irregular waves. One ship is a containership with a relatively small block coefficient and with some bow flare while the other ship is a tanker with a large block coefficient. The wave-induced loads are calculated using a second-order strip theory, derived by a perturbational procedure in which the linear part is identical to the usual strip theory. The additional quadratic terms are determined by taking into account the nonlinearities of the exiting waves, the nonvertical sides of the ship, and, finally, the variations of the hydrodynamic forces during the vertical motion of the ship. The flexibility of the hull is also taken into account. The numerical results show that for the containership a substantial increase in bending moments and shear forces is caused by the quadratic terms. The results also show that for both ships the effect of the hull flexibility (springing) is a fair increase of the variance of the wave-induced midship bending moment. For the tanker the springing is due mainly to exciting forces which are linear with respect to wave heights whereas for the containership the nonlinear exciting forces are of importance.

Reflection effects on wave field within a harbour

1993 ◽  
Vol 20 (3) ◽  
pp. 386-397 ◽  
Author(s):  
Michael Isaacson ◽  
Enda O'Sullivan ◽  
John Baldwin
Keyword(s):  
Numerical Model ◽  
Wave Field ◽  
Wave Reflection ◽  
Diffraction Theory ◽  
Specific Reference ◽  
Wave Source ◽  
Numerical Predictions ◽  
Diffraction Wave ◽  
Reflecting Boundaries ◽  
Reflection Boundary

The present paper outlines a numerical model for predicting the wave field in a harbour with partially reflecting boundaries, and describes laboratory tests undertaken to assess the model. The numerical model is based on linear diffraction theory and involves the application of a partial reflection boundary condition. By utilizing a wave doublet representation of the fluid boundaries instead of the usual wave source representation, the extension is made to general harbour configurations that include breakwaters. Numerical results are compared with known solutions for specific reference configurations. Laboratory measurements have been made of the wave field within a particular harbour model having portions of the boundary corresponding to different degrees of wave reflection. A comparison with the numerical predictions is summarized and highlights the importance of adequately modelling the partial reflections within the harbour. Key words: breakwaters, coastal engineering, harbours, waves, wave diffraction, wave reflection.

Dynamic Modelling of a Spar Buoy Wind Turbine

2017 ◽  
Author(s):  
Giuseppe Roberto Tomasicchio ◽  
Alberto Maria Avossa ◽  
Luigia Riefolo ◽  
Francesco Ricciardelli ◽  
Elena Musci ◽  
...  
Keyword(s):  
Numerical Model ◽  
Wind Turbine ◽  
Dynamic Modelling ◽  
Irregular Waves ◽  
Induced Response ◽  
Simulation Tool ◽  
Floating Structure ◽  
Mooring Lines ◽  
Wave Basin ◽  
Fast Wind

In the present paper, the dynamic response of a spar buoy wind turbine under different wind and wave conditions is discussed. Physical model tests were performed at the Danish Hydraulic Institute (DHI) off-shore wave basin within the EU-Hydralab IV Integrated Infrastructure Initiative. The OC3-Hywind spar buoy was taken as reference prototype. A spar buoy model, 1:40 Froude-scaled, was tested using long crested regular and irregular waves, orthogonal (0 degrees) and oblique (20 degrees) to the structure. Here the results concerning regular waves, with incidence orthogonal to the structure, are presented; the selected tests considered rotating and non-rotating blades. Measurements of displacements, rotations, accelerations, forces response of the floating structure and at the mooring lines were carried out. Based on the observed data, FAST wind turbine simulation tool, developed and maintained by the U.S. Department of Energy’s (DOE’s), National Renewable Energy Laboratory (NREL), was calibrated and verified. The numerical model takes into account the wave induced response and the effects of the mooring lines on the overall system. The adopted spar buoy has three equally spaced mooring lines that were modelled as quasi-static taut or catenary lines through MAP++ (static module) and MoorDyn (dynamic module) in the FAST simulation tool. The tensions along the fairleads of the three mooring lines were examined. At the end of the calibration procedure, the numerical model was successfully used to simulate the dynamic motions of the floating wind turbine under combinations of wind and sea states for the selected wave attacks. All data from the DHI tests were converted to full scale using Froude scaling before being analyzed.

scholarly journals Effects of the Soil Property Distribution Gradient on the Wave-Induced Response of a Non-Homogeneous Seabed

2019 ◽  
Vol 7 (8) ◽  
pp. 281 ◽  
Author(s):  
Titi Sui ◽  
Yu Jin ◽  
Zhaojun Wang ◽  
Chi Zhang ◽  
Jian Shi
Keyword(s):  
Numerical Model ◽  
Dynamic Response ◽  
Soil Properties ◽  
Pore Pressure ◽  
Soil Property ◽  
Induced Response ◽  
Property Distribution ◽  
Effective Stresses ◽  
Soil Distribution ◽  
Wave Induced

The seabed is usually non-homogeneous in the real marine environment, and its response to the dynamic wave loading is of great concern to coastal engineers. Previous studies on the simulation of a non-homogeneous seabed response have mostly adopted a vertically layered seabed, in which homogeneous soil properties are assumed in the governing equations for one specified layer. This neglects the distribution gradient terms of soil property, thus leading to an inaccurate evaluation of the dynamic response of a non-homogeneous seabed. In this study, a numerical model for a wave-induced 3D non-homogeneous seabed response is developed, and the effects of the soil property distribution gradient on the wave-induced response of a non-homogeneous seabed are numerically investigated. The numerical model is validated, and the results of the present simulation agree well with those of previous studies. The validated model is applied to simulate an ideal two-dimensional (2D) vertical non-homogeneous seabed. The model is further applied to model the practical wave-induced dynamic response of a three-dimensional (3D) non-homogeneous seabed around a mono-pile. The difference in pore pressure and soil effective stresses due to the soil distribution gradient is investigated. The effects of the soil distribution gradient on liquefaction are also examined. Results of this numerical study indicate that (1) pore pressure decreases while soil effective stresses increase (the maximum difference of the effective stresses can reach 68.9 % p 0 ) with a non-homogeneous seabed if the distribution gradient terms of soil properties are neglected; (2) the effect of the soil property distribution gradient terms on the pore pressure becomes more significant at the upper seabed, while this effect on the soil effective stresses is enhanced at the lower seabed; (3) the effect of the soil distribution gradient on the seabed response is greatly affected by the wave reflection and diffraction around the pile foundation; and (4) the soil distribution gradient terms can be neglected in the evaluation of seabed liquefaction depth in engineering practice.

A 3-D numerical study of the random wave-induced response in a spatially heterogenous seabed

2021 ◽  
Vol 135 ◽  
pp. 104159
Author(s):  
Bin Zhu ◽  
Tetsuya Hiraishi ◽  
Hajime Mase ◽  
Yasuyuki Baba ◽  
Huafu Pei ◽  
...  
Keyword(s):  
Numerical Study ◽  
Induced Response ◽  
Random Wave ◽  
Wave Induced

Experimental and Numerical Study of the Motions of a Turret Moored FPSO in Waves

2004 ◽  
Vol 127 (3) ◽  
pp. 197-204 ◽  
Author(s):  
C. Guedes Soares ◽  
N. Fonseca ◽  
R. Pascoal
Keyword(s):  
Degrees Of Freedom ◽  
Numerical Study ◽  
Numerical Data ◽  
Irregular Waves ◽  
Experimental Program ◽  
Six Degrees Of Freedom ◽  
Strip Theory ◽  
Wide Range ◽  
Wave Heights ◽  
Mooring Forces

This paper presents the results of an experimental program carried out with a model of a FPSO (Floating Production, Storage and Offloading) unit moored and subjected to incoming waves. In regular waves, a wide range of wavelengths were tested and the effect of the wave amplitude was also investigated. In irregular waves the model was subjected to different sea states, including very severe significant wave heights. The measured responses include the six degrees of freedom absolute motions, relative motions, and the mooring forces. The experimental data of surge, heave, and pitch is compared with calculated results from a Green’s function panel method and a strip theory program. In general, the agreement between experimental and numerical data is very good.

scholarly journals Two-Dimensional Numerical Study of Seabed Response around a Buried Pipeline under Wave and Current Loading

2019 ◽  
Vol 7 (3) ◽  
pp. 66 ◽  
Author(s):  
Cynthia Foo ◽  
Chencong Liao ◽  
Jinjian Chen
Keyword(s):  
Numerical Model ◽  
Pore Pressure ◽  
Numerical Study ◽  
Current Model ◽  
Navier Stokes ◽  
Buried Pipeline ◽  
Soil Permeability ◽  
Biot’S Equation ◽  
Current Loading ◽  
Wave Induced

The evaluation of the wave-induced seabed response around a buried pipeline has been widely studied. However, the analysis of seabed response around marine structures under the wave and current loadings are still limited. In this paper, an integrated numerical model is proposed to examine the wave and current-induced pore pressure generation, for instance, oscillatory and residual pore pressure, around a buried pipeline. The present wave–current model is based on the Reynolds-Averaged Navier–Stokes (RANS) equation with k - ε turbulence while Biot’s equation is adopted to govern the seabed model. Based on this numerical model, it is found that wave characteristics (i.e., wave period), current velocity and seabed characteristics such as soil permeability, relative density, and shear modulus have a significant effect on the generation of pore pressure around the buried pipeline.

Weather and Sea Conditions Offshore New Zealand

1988 ◽  
Vol 6 (2) ◽  
pp. 126-135
Author(s):  
R.K.H. Falconer ◽  
L.J. Handley
Keyword(s):  
New Zealand ◽  
Wind Speed ◽  
Numerical Model ◽  
Data Base ◽  
Wave Height ◽  
Historical Data ◽  
Coastal Engineering ◽  
Oil Exploration ◽  
Southern Area ◽  
Wave Heights

Weather and sea conditions offshore New Zealand are severe enough to be of concern for oil exploration or production, coastal engineering, and shipping; and there have been some bad experiences. Analysis of existing information will permit adequate predictions of likely conditions in most areas. To illustrate the type of data available, and its limitations, examples are presented from the the southern area of New Zealand. Ship report files, particularly those from oil rigs, give adequate indications of wind speed and direction, swell and sea height is reasonable if recalculated as combined wave height, swell directions are adequate, but many sea and swell periods are unreliable. Hinds derived from radar tracked balloons can be used to predict winds up to 250km offshore, which provides a large historical data base. Numerical model derived wave heights correctly indicate the pattern of wave height changes with time, but the amplitudes must be scaled for near site data.

Experimental study of the effect of wind above irregular waves on the wave-induced load statistics

2021 ◽  
pp. 103940
Author(s):  
Julie Caroee Kristoffersen ◽  
Henrik Bredmose ◽  
Christos Thomas Georgakis ◽  
Hubert Branger ◽  
Christopher Luneau
Keyword(s):  
Experimental Study ◽  
Irregular Waves ◽  
Wave Induced
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