scholarly journals Ship generated mini-tsunamis

2017 ◽  
Vol 816 ◽  
pp. 142-166 ◽  
Author(s):  
John Grue
Keyword(s):  
Asymptotic Analysis ◽  
Shallow Water ◽  
Wave Height ◽  
Long Waves ◽  
Qualitative Explanation ◽  
The Waves ◽  
Water Speed ◽  
Shallow Water Depth ◽  
Ship Speed ◽  
Good Agreement

Very long waves are generated when a ship moves across an appreciable depth change $\unicode[STIX]{x0394}h$ comparable to the average and relatively shallow water depth $h$ at the location, with $\unicode[STIX]{x0394}h/h\simeq 1$. The phenomenon is new and the waves were recently observed in the Oslofjord in Norway. The 0.5–1 km long waves, extending across the 2–3 km wide fjord, are observed as run-ups and run-downs along the shore, with periods of 30–60 s, where a wave height up to 1.4 m has been measured. The waves travelling with the shallow water speed, found ahead of the ships moving at subcritical depth Froude number, behave like a mini-tsunami. A qualitative explanation of the linear generation mechanism is provided by an asymptotic analysis, valid for $\unicode[STIX]{x0394}h/h\ll 1$ and long waves, expressing the generation in terms of a pressure impulse at the depth change. Complementary fully dispersive calculations for $\unicode[STIX]{x0394}h/h\simeq 1$ document symmetries of the waves at positive or negative $\unicode[STIX]{x0394}h$. The wave height grows with the ship speed $U$ according to $U^{n}$ with $n$ in the range 3–4, for $\unicode[STIX]{x0394}h/h\simeq 1$, while the growth in $U$ is only very weak for $\unicode[STIX]{x0394}h/h\ll 1$ (the asymptotics). Calculations show good agreement with observations.

scholarly journals WAVE INVESTIGATIONS IN SHALLOW WATER

1970 ◽  
Vol 1 (12) ◽  
pp. 10 ◽  
Author(s):  
Winfried Siefert
Keyword(s):  
Shallow Water ◽  
Wave Height ◽  
Wind Direction ◽  
Tidal Flat ◽  
Propagation Direction ◽  
Elbe Estuary ◽  
Zero Crossing ◽  
Wave Heights ◽  
The Mean ◽  
The Waves

Examination of the significant heights of zero-crossing waves in the Elbe Estuary has yielded two noteworthy results: 1 In the deeper water of the estuary, the value of the quotient relating the significant and the mean wave heights is larger than on the bordering tidal flat. 2. The value of this function is dependent on the height of the waves; on the tidal flat this dependency is considerably more sensitive than in deeper water. With increasing wave height the value of significant wave height divided by mean height becomes smaller The propagation direction of waves moving onto the tidal flat is contingent upon the position of intertidal channels Such channels sharply reduce the possible propagation directions The waves nearly always move up-channel regardless of the wind direction It is possible to derive special wave period and wave height distributions representing the conditions m very shallow water.

scholarly journals DEVELOPMENT OF SHIP WAVE DESIGN INFORMATION

1984 ◽  
Vol 1 (19) ◽  
pp. 216 ◽  
Author(s):  
Robert M. Sorensen ◽  
J. Richard Weggel
Keyword(s):  
Wave Height ◽  
Water Depth ◽  
Additional Data ◽  
Prediction Methods ◽  
Ship Wave ◽  
Wave Prediction ◽  
Laboratory Investigations ◽  
Predictor Model ◽  
The Waves ◽  
Ship Speed

During the last three decades several field and laboratory investigations have been conducted in which the waves generated by a wide variety of vessels have been measured. There is a need to synthesize the data published from these studies and to develop general ship wave prediction methods for designers. To complete this task some additional ship wave data must be collected. This paper initiates the effort to develop these prediction methods. A summary and critique of available data are given. Then, the appropriate portion of these data is employed to develop a ship wave height predictor model that gives the maximum ship wave height as a function of ship speed and displacement, water depth, and distance from the sailing line. This is an interim model that is quite applicable but can be improved pending additional data. Finally, planned future efforts to further develop design wave prediction methods are discussed.

scholarly journals DETERMINATION OF THE WAVE HEIGHT IN NATURE FROM MODEL TESTS SUPPLEMENTED BY CALCULATION

2011 ◽  
Vol 1 (6) ◽  
pp. 12
Author(s):  
J. G.H.R. Diephuis ◽  
J. G. Gerritze
Keyword(s):  
Shallow Water ◽  
Wave Height ◽  
Deep Water ◽  
Bottom Topography ◽  
Model Tests ◽  
Small Scale ◽  
Wave Characteristics ◽  
Sea Bottom ◽  
The Waves

This paper deals with the problem of determining the wave characteristics in shallow water from those in deep water. In general this can be done by means of a refraction calculation. If the sea bottom topography is too irregular the height of the waves can be determined by means of a small-scale refraction model. In both cases, however, some additional effects have to be taken into account, viz. the influence of the bottom friction and the influence of the wind.

scholarly journals OBSERVATIONS OF TIE TRANSFORMATION OF OCEAN WAVE CHARACTERISTICS NEAR COASTS BY USE OF ANCHORED BUOYS

1966 ◽  
Vol 1 (10) ◽  
pp. 6
Author(s):  
Haruo Higuchi ◽  
Tadao Kakinuma
Keyword(s):  
Shallow Water ◽  
Ocean Waves ◽  
Transformation Process ◽  
Long Waves ◽  
Ocean Wave ◽  
Wave Characteristics ◽  
Wave Observation ◽  
The Waves

In order to clarify the transformation process of ocean waves in shallow water, a series of wave observations were carried out along some coasts in Japan by photographing two or three convenient buoys aligned m the direction of the waves with two 16 urn cine-cameras. The equipment and methods used in observations and analyses are here described together with some of the results obtained. By examining the motion of the buoys off the coast at Shirahama it was found that the method of wave observation by means of anchored buoys was very useful in the case of comparatively long waves.

scholarly journals CNOIDAL WAVES IN SHALLOW WATER

1964 ◽  
Vol 1 (9) ◽  
pp. 1
Author(s):  
Frank D. Masch
Keyword(s):  
Shallow Water ◽  
Power Transmission ◽  
Wave Train ◽  
Wave Theory ◽  
Finite Amplitude ◽  
Long Waves ◽  
Practical Application ◽  
Cnoidal Waves ◽  
Water Power ◽  
The Waves

The propagation of long waves of finite amplitude in water with depth to wavelength ratios less than about one-tenth and greater than about one-fiftieth can be described by cnoidal wave theory. To date little use has been made of the theory because of the difficulties involved in practical application. This paper presents the theory necessary for predicting the transforming characteristics of long waves based on cnoidal theory. Basically the method involves calculating the power transmission for a wave train m shallow water from cnoidal theory and equating this to the deep water power transmission assuming no reflections or loss of energy as the waves move into shoaling water. The equations for wave power have been programmed for the range of cnoidal waves, and the results are plotted in non-dimensional form.

Beachpull Installation of Long Pipelines and Cables

2012 ◽  
Author(s):  
Kiran Bhargav ◽  
Senthilkumar Durairaj
Keyword(s):  
Shallow Water ◽  
Joint Venture ◽  
Water Environment ◽  
Unique Challenge ◽  
Dynamic Loadings ◽  
Shallow Water Environment ◽  
Near Shore ◽  
Lateral Displacements ◽  
Shallow Water Depth ◽  
Good Agreement

Conventional pipelay (i.e. S-lay) is not feasible in shallow water locations owing to the draft of pipelay barges. Pipelay using beachpull method provides an alternative to such restrictions. A typical long beachpull operation in shallow water environment presents a substantial challenge, which calls for a thorough engineering analysis along with a detailed installation procedure. This paper highlights the methods and techniques of pipelay using beachpull method that were employed on the John Brookes joint venture (Apache and Santos) and the Aramco Karan project. The John Brookes project (Varanus Island, Australia) included the installation of a landfall section comprising an 18” FBE coated pipeline featuring a beachpull length of 7.0 km, one of the longest of its kind. The Karan project (Saudi Arabia) comprised the installation of a 38” trunkline, requiring a beachpull length of 3.0 km and also the installation of a 15kV cable having a beachpull length of 4.0 km. Beachpull engineering comprised checking the pipeline’s lateral stability under the influence of near-shore current-induced hydrodynamic forces. For the Apache Project, the 7.0 km long beachpull coupled with the proximity to the existing pipeline and near-shore currents offered a unique challenge. Supplementary buoyancy was utilized to limit the required beachpull tension within allowable limits. The drifting of the pipeline from the installation corridor was restricted by installing sand-filled bulker bags at designed intervals. The beachpull installation on the Karan project offered a different challenge owing to a larger pipe size and a piggybacked cable in a shallow water depth. Special consideration was given to the attachment of supplementary buoyancy bags and dynamic loadings that were acting throughout the beachpull length, especially during cable installation. This paper describes the technical challenges faced during the estimation of the pull-in loads and weather-induced lateral displacements encountered during the beachpull. This paper also elaborates the assessment of proposed winch, design of supplementary buoyancy, design of bulker bags, etc. Data collected on-site during installation of the pipelines are in good agreement with computed / designed values, ensuring the correctness of the beachpull simulations. Detailed engineering studies along with well developed installation procedures resulted in successful completion of the installation.

scholarly journals Wave Force Characteristics of Large-Sized Offshore Wind Support Structures to Sea Levels and Wave Conditions

2019 ◽  
Vol 9 (9) ◽  
pp. 1855
Author(s):  
Youn-Ju Jeong ◽  
Min-Su Park ◽  
Jeongsoo Kim ◽  
Sung-Hoon Song
Keyword(s):  
Shallow Water ◽  
Wave Height ◽  
Wave Force ◽  
Diffraction Effect ◽  
Support Structures ◽  
Sea Levels ◽  
Irregular Wave ◽  
Long Period ◽  
Short Period ◽  
Period Wave

This paper presents the results of wave force tests conducted on three types of offshore support structures considering eight waves and three sea levels to investigate the corresponding wave forces. As a result of this study, it is found that the occurrence of shoaling in shallow water induces a significant increase of the wave force. Most of the test models at the shallow water undergo a nonlinear increase of the wave force with higher wave height increasing. In addition, the larger the diameter of the support structure within the range of this study, the larger the diffraction effect is, and the increase in wave force due to shoaling is suppressed. Under an irregular wave at the shallow water, the wave force to the long-period wave tends to be slightly higher than that of the short period wave since the higher wave height component included in the irregular wave has an influence on the shoaling. In addition, it is found that the influence of shoaling under irregular wave becomes more apparent in the long period.

Validity of the Finite Fracture Mechanics Based Asymptotic Analysis for Predictions of Crack Deflection in Thin Layers of Ceramic Laminates

2014 ◽  
Vol 627 ◽  
pp. 237-240 ◽  
Author(s):  
Oldřich Ševeček ◽  
Dominique Leguillon ◽  
Tomáš Profant ◽  
Michal Kotoul
Keyword(s):  
Potential Energy ◽  
Asymptotic Solution ◽  
Asymptotic Analysis ◽  
Crack Extension ◽  
Crack Deflection ◽  
Thin Layers ◽  
Reference Solution ◽  
Finite Fracture Mechanics ◽  
Higher Order Terms ◽  
Good Agreement

The work studies and compares different approaches suitable for predictions of the crack deflection (bifurcation) in ceramic laminates containing thin layers under high residual stresses and discuss a suitability and limits of using of the asymptotic analysis for such problems. The thickness of the thin compressive layers where the crack deflection occurs is only one order higher than the crack extension lengths considered within the solution. A purely FEM based calculation of the energy and stress conditions, necessary for the crack propagation, serves as the reference solution to the problem. The asymptotic analysis is used after for calculations of the same quantities (especially of energy release rate – ERR). This concept enables semi-analytical calculations of ERR or changes in potential energy induced by the crack extensions of different lengths and directions. Such approach can save a large amount of simulations and time compared with the pure FEM based calculations. It was found that the asymptotic analysis provides a good agreement for investigations of the crack increments enough far from the adjacent interfaces but for longer extensions (of length above 1/5-1/10 of the distance from the interface) starts more significantly to deviate from the correct solution. Involvement of the higher order terms in the asymptotic solution or other improvement of the model is thus advisable.

Stability of offshore structures in shallow water depth

2011 ◽  
Vol 2 (2) ◽  
pp. 320-333
Author(s):  
F. Van den Abeele ◽  
J. Vande Voorde
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Fossil Fuels ◽  
Oil And Gas ◽  
Structural Response ◽  
Offshore Structures ◽  
Exploration And Production ◽  
Subsea Pipelines ◽  
Wave Induced ◽  
Shallow Water Depth

The worldwide demand for energy, and in particular fossil fuels, keeps pushing the boundaries of offshoreengineering. Oil and gas majors are conducting their exploration and production activities in remotelocations and water depths exceeding 3000 meters. Such challenging conditions call for enhancedengineering techniques to cope with the risks of collapse, fatigue and pressure containment.On the other hand, offshore structures in shallow water depth (up to 100 meter) require a different anddedicated approach. Such structures are less prone to unstable collapse, but are often subjected to higherflow velocities, induced by both tides and waves. In this paper, numerical tools and utilities to study thestability of offshore structures in shallow water depth are reviewed, and three case studies are provided.First, the Coupled Eulerian Lagrangian (CEL) approach is demonstrated to combine the effects of fluid flowon the structural response of offshore structures. This approach is used to predict fluid flow aroundsubmersible platforms and jack-up rigs.Then, a Computational Fluid Dynamics (CFD) analysis is performed to calculate the turbulent Von Karmanstreet in the wake of subsea structures. At higher Reynolds numbers, this turbulent flow can give rise tovortex shedding and hence cyclic loading. Fluid structure interaction is applied to investigate the dynamicsof submarine risers, and evaluate the susceptibility of vortex induced vibrations.As a third case study, a hydrodynamic analysis is conducted to assess the combined effects of steadycurrent and oscillatory wave-induced flow on submerged structures. At the end of this paper, such ananalysis is performed to calculate drag, lift and inertia forces on partially buried subsea pipelines.

scholarly journals The spin-up of a linearly stratified fluid in a sliced, circular cylinder

2016 ◽  
Vol 806 ◽  
pp. 254-303
Author(s):  
R. J. Munro ◽  
M. R. Foster
Keyword(s):  
Circular Cylinder ◽  
Rossby Waves ◽  
Rotation Axis ◽  
A Priori ◽  
Propagation Speed ◽  
Stratified Fluid ◽  
Decay Rates ◽  
The Waves ◽  
Western Half ◽  
Good Agreement

A linearly stratified fluid contained in a circular cylinder with a linearly sloped base, whose axis is aligned with the rotation axis, is spun-up from a rotation rate $\unicode[STIX]{x1D6FA}-\unicode[STIX]{x0394}\unicode[STIX]{x1D6FA}$ to $\unicode[STIX]{x1D6FA}$ (with $\unicode[STIX]{x0394}\unicode[STIX]{x1D6FA}\ll \unicode[STIX]{x1D6FA}$) by Rossby waves propagating across the container. Experimental results presented here, however, show that if the Burger number $S$ is not small, then that spin-up looks quite different from that reported by Pedlosky & Greenspan (J. Fluid Mech., vol. 27, 1967, pp. 291–304) for $S=0$. That is particularly so if the Burger number is large, since the Rossby waves are then confined to a region of height $S^{-1/2}$ above the sloped base. Axial vortices, ubiquitous features even at tiny Rossby numbers of spin-up in containers with vertical corners (see van Heijst et al.Phys. Fluids A, vol. 2, 1990, pp. 150–159 and Munro & Foster Phys. Fluids, vol. 26, 2014, 026603, for example), are less prominent here, forming at locations that are not obvious a priori, but in the ‘western half’ of the container only, and confined to the bottom $S^{-1/2}$ region. Both decay rates from friction at top and bottom walls and the propagation speed of the waves are found to increase with $S$ as well. An asymptotic theory for Rossby numbers that are not too large shows good agreement with many features seen in the experiments. The full frequency spectrum and decay rates for these waves are discussed, again for large $S$, and vertical vortices are found to occur only for Rossby numbers comparable to $E^{1/2}$, where $E$ is the Ekman number. Symmetry anomalies in the observations are determined by analysis to be due to second-order corrections to the lower-wall boundary condition.

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