scholarly journals Wave-induced loads on a lock gate provided with an opening through the ballast tank

2020 ◽  
Vol 6 (4) ◽  
pp. 415-425
Author(s):  
Luca Cavallaro ◽  
Claudio Iuppa ◽  
Pietro Scandura ◽  
Enrico Foti
Keyword(s):  
Mathematical Model ◽  
Wave Theory ◽  
Maximum Load ◽  
Wave Number ◽  
Linear Wave ◽  
Vertical Force ◽  
Wave Loads ◽  
Wave Load ◽  
Ballast Tank ◽  
Lock Gate

AbstractThe wave loads on a navigation lock gate provided with an opening in the ballast tank are analyzed using a mathematical model based on the linear wave theory. The analysis focuses on the influence of the wave number and the geometrical characteristics of the structure on the applied load. It is shown that the maximum value of the vertical force mainly depends on the height of the ballast tank and on the width of the opening. The wave number for which the maximum load occurs significantly depends on the geometric characteristics of the structure except for the water depth above the ballast tank which has a negligible effect. An increase in the height of the ballast tank causes an increase in the wave load while an increase in the width of the opening causes a decrease in the wave load. Based on the results of the mathematical model an easy to use regression model has been developed which can be employed to evaluate the wave load.

scholarly journals WAVE LOADS ON A NAVIGATION LOCK SLIDING GATE: NON-LINEAR EFFECTS

2020 ◽  
pp. 8
Author(s):  
Luca Cavallaro ◽  
Claudio Iuppa ◽  
Rosaria Ester Musumeci ◽  
Pietro Scandura ◽  
Enrico Foti
Keyword(s):  
Analytical Model ◽  
Cfd Simulation ◽  
Analytical Models ◽  
Wave Number ◽  
Linear Wave ◽  
Vertical Force ◽  
Wave Loads ◽  
Vertical Load ◽  
Non Linear ◽  
Navigation Lock

The wave loads on a navigation lock gate provided with an opening in the ballast tank are analyzed using a mathematical model based on the linear wave theory and the numerical integration of the Navier-Stokes Equation. The analysis focuses on the evaluation of the non-linear effect influence on the vertical load on the gate. It is shown that the numerical and analytical models agree on the identification of the value of the wave number at which the maximum value of the dimensionless vertical force on the gate is detected. However the analytical model overestimates the peak value of the vertical load with respect to the CFD simulation. To fill this gap, in this paper an easy to use procedure is developed which allows to correct the results of the analytical model.

Calculation of Wave Forces Acting on a Cylinder With a Porous Plate Fixed Inside

2009 ◽  
Author(s):  
Weiguang Bao ◽  
Fenfang Zhao ◽  
Takeshi Kinoshita
Keyword(s):  
Body Surface ◽  
Porous Body ◽  
Porous Plate ◽  
Wave Theory ◽  
Wave Forces ◽  
Linear Wave ◽  
Normal Velocity ◽  
Wave Loads ◽  
Eigen Values ◽  
Eigen Function

To evaluate wave forces and to estimate the motion of breakwater, a circular cylinder is investigated based on the linear wave theory in the present work. The cylinder possesses a porous sidewall, an impermeable bottom and a horizontal porous plate inside that is fixed in the cylinder to work as obstruct and make wave dissipation more effectively. To simplify the problem, the Darcy’s fine-pore model is applied to the boundary condition on the porous body surface. The boundary value problem is solved by means of the eigen-function expansion approach. The fluid domain is divided into three regions and different eigen-function series are used. The so-called dispersion relation for the region inside the cylinder is quite different from a conventional one due to the existence of the porous plate. It leads to eigen values of complex number. To obtain solutions for the radiation problems, particular solution should be constructed to take account of the normal velocity appearing on the porous boundary. The wave loads are evaluated by integrating the pressure difference on two sides of the wetted body surface. The theoretical works are in good consistence with the experimental results. The Haskind relations are examined for the porous body. It is found that the damping coefficient consists of two parts. In addition to the component of conventional wave-radiating damping, exists a second component caused by the porous effects.

Influence of Second-Order Difference-Frequency Wave Loads on the Floating Wind-Wave Hybrid Platform

2017 ◽  
Author(s):  
Hyebin Lee ◽  
Yoon Hyeok Bae ◽  
Kyong-Hwan Kim ◽  
Sewan Park ◽  
Keyyong Hong
Keyword(s):  
Wind Wave ◽  
Computational Effort ◽  
Second Order ◽  
Difference Frequency ◽  
Linear Wave ◽  
Wave Loads ◽  
Wave Load ◽  
Frequency Wave ◽  
Order Difference ◽  
Hybrid Platform

A wind-wave hybrid power generation system is a floating offshore energy platform which is equipped with a number of wind turbines and wave energy converters (WECs) to harvest energy from various resources. This wind-wave hybrid platform is moored by eight catenary lines to keep its position against wind-wave-current environment. In most cases, the resonant frequency of horizontal motion of moored platform is very low, so a resonance is hardly seen by numerical simulation with linear wave assumptions. However, the incident waves with different frequency components are accompanied by sum and difference frequency loads due to the nonlinearity of the waves. Typically, the magnitude of the second-order wave loads are small and negligible, but once the second-order wave loads excite the platform at its natural frequency, the resonance can take place, which results in adverse effects on the platform. In this paper, the second-order difference frequency wave load on the wind-wave hybrid platform is numerically assessed and time domain simulation by coupled platform-mooring dynamic analysis is carried out. As a result, the horizontal motions of the platform was highly excited and the increased motions led higher top tension of the mooring lines compared with the case of linear wave environment. Especially, the combination of the wind and wave loads excited the horizontal motions more and made the mooring top tension far higher than wave load was only applied. With regards to the second-order difference frequency wave load, the result with the Quadratic Transfer Function (QTF) is compared to the one with Newman’s approximation. As the simulation results between them was insignificant, the Newman’s approximation can be used instead of the complete QTF to reduce the computational effort.

Calculated Dynamic Response of an Articulated Tower in Waves—Comparison With Model Tests

1987 ◽  
Vol 109 (1) ◽  
pp. 43-51 ◽  
Author(s):  
T. E. Schellin ◽  
T. Koch
Keyword(s):  
Dynamic Response ◽  
Axial Flow ◽  
Wave Theory ◽  
Diffraction Theory ◽  
Model Tests ◽  
Linear Wave ◽  
Vertical Force ◽  
Hydrodynamic Coefficients ◽  
Test Results ◽  
Statistical Measures

Calculated dynamic response of an articulated tower in waves is compared with model tests. The theory used is based on Morison’s equation and linear wave theory and requires specified hydrodynamic force coefficients. Calculations are done with three different sets of coefficients. Firstly, coefficients are assumed not to vary with wave period. Secondly, they are selected from experimental data of oscillating flow past stationary cylinders. Thirdly, they are based on calculations using diffraction theory. Added mass and inertia coefficients have a predominant effect on calculated response, drag coefficients have almost no effect. Calculated tower top motion and horizontal force at the universal joint correlate well for all three sets of coefficients, indicating that hydrodynamic coefficients for normal flow are reasonably well selected and need not be specified with undue precision. In contrast, hydrodynamic coefficients for axial flow need to be chosen carefully. Calculated vertical force at the joint, using initially specified axial flow coefficients, correlates poorly with measurements. Correlation is greatly improved using reduced coefficients for axial flow. Calculated response is reasonably linear with wave height. Spectral analysis techniques are used to determine statistical measures for three irregular seastates. Agreement with corresponding model test results is satisfactory.

Stability of Artificial Subaqueous Slopes in Sandy Soils Under Wave Loads

2015 ◽  
Author(s):  
Julian Bubel ◽  
Marc-André Pick ◽  
Jürgen Grabe
Keyword(s):  
Surface Waves ◽  
Wave Length ◽  
Ground Surface ◽  
Sandy Soils ◽  
Wave Theory ◽  
Friction Angle ◽  
Shallow Foundation ◽  
Cohesionless Soil ◽  
Linear Wave ◽  
Wave Loads

Shallow foundation structures in marine environments can rarely be placed on top of the sea floor. Weak soils usually need to be excavated to place the structure on more stable ground. Steep but stable slopes of the resulting pit meet both economic and ecologic aims as they minimise material movement and sediment disturbance. This paper focuses changes of geometry of submarine slopes in non-cohesive soils (erosion, sedimentation, breach failure, liquefaction failure) due to surface waves. After Terzaghi the angle between slope and the horizontal of the ground surface of cohesionless soil is at most equal to the critical state friction angle, as obviously true for dry soil. However, it can be observed that natural submarine slopes of sandy soils are always mildly sloped. During the construction of artificial submarine pits under offshore conditions it should be considered that the long-term slope-inclination is less than onshore due to hydrodynamic actions (e. g. flow, waves, earthquakes). Large surface waves cause excess pore water pressures within the soil body, leading to a reduction of effective stresses and in case of submarine slopes to changes of the slope geometry depending on wave length L, wave height H, water depth h and soil properties (permeability k, relative density Dr). During our preliminary work we investigated such processes based on the coupling of linear wave theory and linear quasistatic consolidation theory (e.g. [1]). With the help of numerical modelling we solved corresponding equations considering also materially nonlinear consolidation. However, deformations were always limited by used Lagrangian-FEM. Recent developments at our Institute enable the use of an Eulerian-FEM approach with an u-p-Formulation for fully saturated soil [2]. This allows larger deformations of the subaqueous slope to be numerically investigated.

scholarly journals Wave-Generated Current: A Second-Order Formulation

2020 ◽  
Vol 8 (6) ◽  
pp. 418
Author(s):  
Anne Katrine Bratland
Keyword(s):  
Wave Theory ◽  
Second Order ◽  
Stokes Drift ◽  
Wave Number ◽  
Stokes Wave ◽  
Wave Loads ◽  
Third Order ◽  
The Third ◽  
Computational Fluid Dynamics Cfd ◽  
The Mean

In Stokes’ wave theory, wave numbers are corrected in the third order solution. A change in wave number is also associated with a change in current velocity. Here, it will be argued that the current is the reason for the wave number correction, and that wave-generated current at the mean free surface in infinite depth equals half the Stokes drift. To demonstrate the validity of this second-order formulation, comparisons to computational fluid dynamics (CFD) results are shown; to indicate its effect on wave loads on structures, model tests and analyses are compared.

Fatigue Strength Assessment Analysis of Large Container Ship

2014 ◽  
Vol 602-605 ◽  
pp. 385-389 ◽  
Author(s):  
Feng Lei Han ◽  
Chun Hui Wang ◽  
An Kang Hu ◽  
Ya Chong Liu
Keyword(s):  
Fatigue Strength ◽  
Hot Spot ◽  
Direct Calculation ◽  
Linear Wave ◽  
Container Ship ◽  
Wave Loads ◽  
Wave Load ◽  
Strength Assessment ◽  
Fatigue Strength Assessment ◽  
Large Container

Fatigue assessments of container ship structures can be processed using various direct calculation approaches or various approaches of classification societies [1,2]. In this investigation, the fatigue strength assessment to the key positions of a 9200TEU container ship has been performed ,subjected to the rules of BV about fatigue strength specification of large container ships, based on design wave method and Miner fatigue cumulative damage theory analysis method. Wave loads have been computed using linear wave load calculation method based on three-dimensional potential flow theory. And the fatigue strength assessment of the typical hot spot structures has also been conducted based on a series of critical single design wave.

scholarly journals An Experimental Investigation of Wave Forces on a Submerged Horizontal Plate over a Simple Slope

2020 ◽  
Vol 8 (7) ◽  
pp. 507
Author(s):  
Jie Dong ◽  
Leiping Xue ◽  
Kaiyu Cheng ◽  
Jian Shi ◽  
Chi Zhang
Keyword(s):  
Wave Length ◽  
Wave Forces ◽  
Linear Wave ◽  
Intermediate Water ◽  
Vertical Force ◽  
Wave Loads ◽  
Horizontal Plate ◽  
Flat Bottom ◽  
Simple Slope ◽  
Submerged Horizontal Plate

We experimentally investigated the forces induced by monochromatic and solitary waves on a submerged horizontal plate in a wave flume. The experimental results of two-dimensional wave forces on the plate over a 1:10 simple slope and a flat bottom are presented. The effects of the uneven bottom on wave loads are discussed by comparing the results with those in a constant water depth. The measured nonlinear wave forces exhibited considerable discrepancies with the theoretical results from the linear wave theory. The wave forces on the plate induced by monochromatic waves over the simple slope in intermediate water showed no appreciable difference with the flat-bottom results. The solitary wave forces in terms of the downward vertical force and overturning moment significantly decreased in the existence of the simple slope. Furthermore, the dependency of the wave length, wave height and the submergence depth on the wave loads is also discussed.

scholarly journals Theoretical Hydrodynamic Analysis of a Surface-Piercing Porous Cylindrical Body

Fluids ◽  
2021 ◽  
Vol 6 (9) ◽  
pp. 320
Author(s):  
Dimitrios N. Konispoliatis ◽  
Ioannis K. Chatjigeorgiou ◽  
Spyridon A. Mavrakos
Keyword(s):  
Water Waves ◽  
Wave Attenuation ◽  
Three Dimensional ◽  
Cylindrical Body ◽  
Expansion Method ◽  
Wave Theory ◽  
Linear Wave ◽  
Wave Loads ◽  
Dimensional Solution ◽  
Eigenfunction Expansion Method

In the present study, the diffraction and the radiation problems of water waves by a surface-piercing porous cylindrical body are considered. The idea conceived is based on the capability of porous structures to dissipate the wave energy and to minimize the environmental impact, developing wave attenuation and protection. In the context of linear wave theory, a three-dimensional solution based on the eigenfunction expansion method is developed for the determination of the velocity potential of the flow field around the cylindrical body. Numerical results are presented and discussed concerning the wave elevation and the hydrodynamic forces on the examined body for various values of porosity coefficients. The results revealed that porosity plays a key role in reducing/controlling the wave loads on the structure and the wave run-up, hence porous barriers can be set up to protect a marine structure against wave attack.

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