scholarly journals WAVE LOADS ASSESSMENT FOR SUBMERGED WATER INTAKE DESIGN

2018 ◽  
pp. 56 ◽  
Author(s):  
Shen Saoxian ◽  
Zhang Yang ◽  
Andrew Cornett
Keyword(s):  
Water Intake ◽  
Physical Modeling ◽  
Breaking Waves ◽  
Wave Forces ◽  
Wave Loads ◽  
Test Results ◽  
Large Size ◽  
Intake Pipe ◽  
Wave Induced ◽  
Wave Properties

Estimating wave-induced forces on water intake is challenging, particularly for large size intake (up to 15m in its cap diameter) subject to breaking waves in shallow water. The relationships between wave properties and wave loads are not well understood, and no simple methods are available to predict hydrodynamic loads on submerged intakes, particularly under breaking waves. This paper attempts to provide a method of assessing wave forces on water intake pipe and velocity cap using the Froude-Krylov formula, based on physical modeling test results for submerged intake under breaking waves.

Characteristics of the Wave Slamming Forces on Jacket Structures Under Plunging Breaking Waves Based on Experimental Data

2017 ◽  
Author(s):  
Jithin Jose ◽  
Olga Podrażka ◽  
Ove Tobias Gudmestad ◽  
Witold Cieślikiewicz
Keyword(s):  
Energy Demand ◽  
Clean Energy ◽  
Breaking Waves ◽  
Offshore Structures ◽  
Offshore Wind ◽  
Wave Forces ◽  
Breaking Wave ◽  
Jacket Structures ◽  
Wave Slamming ◽  
Wave Properties

Due to increased energy demand and thrive for clean energy, offshore wind energy has become popular these days. A large number of offshore wind turbines supported by fixed type substructures have been installed, among which jacket structures are getting popular in recent times. The forces from breaking waves are a major concern in the design of offshore structures installed in shallow waters. However, there are only limited studies available regarding breaking wave forces on jacket structures and still there exist many uncertainties in this area. During the WaveSlam experiment carried out in 2013, a jacket structure of 1:8 scale was tested on a large number of breaking wave conditions. Wave properties and the forces on the structure were measured during the experiment. The total wave slamming forces are being filtered from the experimental measured force using the Empirical Mode Decomposition method and local slamming forces are obtained by the Frequency Response Function method. Based on these results, the peak slamming force and slamming coefficients on the jacket members are estimated. The wave parameters (wave height and period) and wave front asymmetry are obtained from measured wave properties. The variation of slamming forces and slamming coefficients with respect to these parameters are also investigated.

scholarly journals Experimental Evidence of the Influence of Recurves on Wave Loads at Vertical Seawalls

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 889 ◽  
Author(s):  
Dimitris Stagonas ◽  
Rajendran Ravindar ◽  
Venkatachalam Sriram ◽  
Stefan Schimmels
Keyword(s):  
Large Scale ◽  
Vertical Wall ◽  
Breaking Waves ◽  
Wave Loads ◽  
Incoming Wave ◽  
Wave Heights ◽  
The Mean ◽  
Peak Pressures ◽  
Wave Induced ◽  
Incident Waves

The role of recurves on top of seawalls in reducing overtopping has been previously shown but their influence in the distribution and magnitude of wave-induced pressures and forces on the seawall remains largely unexplored. This paper deals with the effects of different recurve geometries on the loads acting on the vertical wall. Three geometries with different arc lengths, or extremity angles (αe), were investigated in large-scale physical model tests with regular waves, resulting in a range of pulsating (non-breaking waves) to impulsive (breaking waves) conditions at the structure. As the waves hit the seawall, the up-rushing flow is deflected seawards by the recurve and eventually, re-enters the underlying water column and interacts with the next incoming wave. The re-entering water mass is, intuitively, expected to alter the incident waves but it was found that the recurve shape does not affect wave heights significantly. For purely pulsating conditions, the influence of αe on peak pressures and forces was also negligible. In marked contrast, the mean of the maximum impulsive pressure and force peaks increased, even by a factor of more than two, with the extremity angle. While there is no clear relation between the shape of the recurve and the mean peak pressures and forces, interestingly the mean of the 10% highest forces increases gradually with αe and this effect becomes more pronounced with increasing impact intensity.

Numerical Simulations of Breaking Waves and Steep Waves Past a Vertical Cylinder at Different Keulegan–Carpenter Numbers

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Shengnan Liu ◽  
Muk Chen Ong ◽  
Charlotte Obhrai
Keyword(s):  
Dynamic Pressure ◽  
Vertical Cylinder ◽  
Breaking Waves ◽  
Numerical Results ◽  
Wave Forces ◽  
Breaking Wave ◽  
Wave Loads ◽  
Time Step ◽  
Two Phase ◽  
Steep Waves

A three-dimensional (3D) numerical two-phase flow model based on solving unsteady Reynolds-averaged Navier–Stokes (URANS) equations has been used to simulate breaking waves and steep waves past a vertical cylinder on a 1:10 slope. The volume of fluid (VOF) method is employed to capture the free surface and the k–ω shear–stress transport (k–ω SST) turbulence model is used to simulate the turbulence effects. Mesh and time-step refinement studies have been conducted. The numerical results of wave forces on the structure are compared with the experimental data (Irschik et al., 2004, “Breaking Wave Loads on a Slender Pile in Shallow Water,” Coastal Engineering, Vol. 4, World Scientific, Singapore, pp. 568–581) to validate the numerical model, and the numerical results are in good agreement with the measured data. The wave forces on the structure at different Keulegan–Carpenter (KC) numbers are discussed in terms of the slamming force. The secondary load cycles are observed after the wave front past the structure. The dynamic pressure and velocity distribution, as well as the characteristics of the vortices around the structure at four important time instants, are studied.

Effect of Seabed Imperfection on the Buckling of Buried Pipelines Subjected to Wave-Induced Loads

2019 ◽  
Author(s):  
D. Suresh Kumar ◽  
M. R. Sunny ◽  
T. Sahoo
Keyword(s):  
High Pressures ◽  
Wave Forces ◽  
Wave Loads ◽  
Buried Pipelines ◽  
Soil Medium ◽  
Finite Element Software ◽  
Pore Pressures ◽  
Buckling Behavior ◽  
Wave Induced ◽  
Uplift Forces

Abstract Subsea pipelines operating under high pressures and temperatures are typically buried to protect from the environmental impacts and to prevent the instigation of global buckling. As the seabed profile is generally uneven, certain initial imperfections generally exist along the pipeline. As the pipe traverses in shallow waters, the seabed can be subjected to hydrodynamic loads caused by surface gravity waves. The hydrodynamic pressure, which typically depends on the wave height and water depth, leads to the development of pore pressures within the soil medium. This gradient of the pore pressures can cause significant uplift forces on the pipe, which may initiate the buckling in the vicinity of the imperfection. This study focuses on understanding the influence of these wave induced uplift forces on the buckling of the initial imperfect pipelines. Four typical imperfection profiles are considered in the study. The influence of imperfection shape on the buckling behavior is compared for surface laid and buried pipelines. Thereafter buckling behavior of the considered imperfect pipelines is studied with and without consideration of wave loads for a range of wave particulars and burial depths. The wave forces on the pipeline are estimated by solving Biot’s consolidation equations using finite element software COMSOL and the buckling studies are carried out using ABAQUS.

Flow and flexibility. II. The roles of size and shape in determining wave forces on the bull kelp nereocystis luetkeana

1997 ◽  
Vol 200 (24) ◽  
pp. 3165-3183 ◽  
Author(s):  
M Denny ◽  
B Cowen
Keyword(s):  
Laboratory Tests ◽  
Flexible Structures ◽  
General Rule ◽  
Ocean Waves ◽  
Wave Forces ◽  
Large Size ◽  
Nereocystis Luetkeana ◽  
Stipe Length ◽  
Inertial Loading ◽  
Wave Induced

Giant kelps (which may reach lengths of 45 m) are a prominent exception to the general rule that wave-swept organisms are small. The ability of these kelps to maintain their large size in the presence of ocean waves has been attributed to their extreme flexibility and the concomitant tendency to 'go with the flow', a tendency that reduces the hydrodynamic forces imposed on the plant. However, the flexibility of giant kelps carries with it the potential for the organism to apply an inertial load to its own structure if the blade mass reaches the end of its tether. Here, we examine the complex trade-off between flexibility and inertial loading using a simple computational model of the bull kelp Nereocystis luetkeana. In field and laboratory tests, the model accurately predicts the forces and motions imposed on flexible structures in wave-induced flows. Subsequent predictions from the model suggest that mature N. luetkeana can indeed benefit from moving with the flow, but that the forces imposed on juveniles are actually increased by the plant's flexibility. Furthermore, the benefit accrued from going with the flow is sensitive to the shape of the plant. If the bull kelp were to grow while maintaining a juvenile shape, the stress placed on its stipe would be drastically increased by dynamic loading, and these inappropriately shaped plants would be subjected to a high risk of breakage. For certain combinations of wave height, wave period and stipe length, the increased stress in hypothetical 'small'-shaped plants may be associated with chaotic motion of the blade mass.

scholarly journals DYNAMIC FORCES DUE TO WAVES BREAKING AT VERTICAL COASTAL STRUCTURES

1988 ◽  
Vol 1 (21) ◽  
pp. 186 ◽  
Author(s):  
Hans-Werner Partenscky
Keyword(s):  
Breaking Waves ◽  
Wave Forces ◽  
Test Results ◽  
Coastal Structures ◽  
Design Wave Height ◽  
Dynamic Forces ◽  
The Difference ◽  
Almost All ◽  
The Impact ◽  
Empirical Approaches

In the past 20 years, considerable effort has been devoted to replacing the widely used approaches of HIROI, MINIKIN, NAGAI, PLAKIDA and others /1,2,3,4/, for the design of vertical breakwaters under the impact of breaking waves, with improved and more exact calculation methods. However, almost all new theoretical and empirical approaches lacked the support of prototype measurements or test results from model measurements at a larger scale. The difference between the proposed design criteria and classical approaches is sometimes so great that engineers do not have a reliable method for the design of a vertical or composite breakwater. Figure 1 shows the resulting wave forces per unit width due to different theories as a function of the design wave height H.

scholarly journals Characteristics of Breaking Wave Forces on Piles over a Permeable Seabed

2021 ◽  
Vol 9 (5) ◽  
pp. 520
Author(s):  
Zhenyu Liu ◽  
Zhen Guo ◽  
Yuzhe Dou ◽  
Fanyu Zeng
Keyword(s):  
Wave Breaking ◽  
Stokes Equations ◽  
Slope Angle ◽  
Wave Force ◽  
Breaking Waves ◽  
Offshore Wind ◽  
Secondary Wave ◽  
Wave Forces ◽  
Breaking Wave ◽  
Breaking Wave Forces

Most offshore wind turbines are installed in shallow water and exposed to breaking waves. Previous numerical studies focusing on breaking wave forces generally ignored the seabed permeability. In this paper, a numerical model based on Volume-Averaged Reynolds Averaged Navier–Stokes equations (VARANS) is employed to reveal the process of a solitary wave interacting with a rigid pile over a permeable slope. Through applying the Forchheimer saturated drag equation, effects of seabed permeability on fluid motions are simulated. The reliability of the present model is verified by comparisons between experimentally obtained data and the numerical results. Further, 190 cases are simulated and the effects of different parameters on breaking wave forces on the pile are studied systematically. Results indicate that over a permeable seabed, the maximum breaking wave forces can occur not only when waves break just before the pile, but also when a “secondary wave wall” slams against the pile, after wave breaking. With the initial wave height increasing, breaking wave forces will increase, but the growth can decrease as the slope angle and permeability increase. For inclined piles around the wave breaking point, the maximum breaking wave force usually occurs with an inclination angle of α = −22.5° or 0°.

scholarly journals Determination of Force Coefficients for a Submerged Rigid Breakwater under the Action of Solitary Waves

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 315
Author(s):  
Francesco Aristodemo ◽  
Giuseppe Tripepi ◽  
Luana Gurnari ◽  
Pasquale Filianoti
Keyword(s):  
Solitary Waves ◽  
Pressure Sensors ◽  
Wave Forces ◽  
Wave Loads ◽  
Force Coefficients ◽  
Wave Flume ◽  
Physical Tests ◽  
The Difference ◽  
The University ◽  
Semi Empirical

We present an analysis related to the evaluation of Morison and transverse force coefficients in the case of a submerged square barrier subject to the action of solitary waves. To this purpose, two-dimensional experimental research was undertaken in the wave flume of the University of Calabria, in which a rigid square barrier was provided by a discrete battery of pressure sensors to determine the horizontal and vertical hydrodynamic forces. A total set of 18 laboratory tests was carried out by varying the motion law of a piston-type paddle. Owing to the low Keulegan–Carpenter numbers of the tests, the force regime of the physical tests was defined by the dominance of the inertia loads in the horizontal direction and of the lift loads in the vertical one. Through the use of the time series of wave forces and the undisturbed kinematics, drag, horizontal inertia, lift, and vertical inertia coefficients in the Morison and transverse semi-empirical schemes were calculated using time-domain approaches, adopting the WLS1 method for the minimization of the difference between the maximum forces and the linked phase shifts by comparing laboratory and calculated wave loads. Practical equations to calculate these coefficients as a function of the wave non-linearity were introduced. The obtained results highlighted the prevalence of the horizontal forces in comparison with the vertical ones which, however, prove to be fundamental for stability purposes of the barrier. An overall good agreement between the experimental forces and those calculated by the calibrated semi-empirical schemes was found, particularly for the positive horizontal and vertical loads. The analysis of the hydrodynamic coefficients showed a decreasing trend for the drag, horizontal inertia, and lift coefficients as a function of the wave non-linearity, while the vertical inertia coefficient underlined an initial increasing trend and a successive slight decreasing trend.

scholarly journals Prediction of Effects of Geogrid Reinforced Granular Fill on the Behaviour of Static Liquefaction

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
A. Hemalatha ◽  
N. Mahendran ◽  
G. Ganesh Prabhu
Keyword(s):  
Bearing Capacity ◽  
Load Test ◽  
Test Results ◽  
Plate Load Test ◽  
Large Size ◽  
Static Liquefaction ◽  
Granular Fill ◽  
Size Dimension ◽  
Subgrade Modulus ◽  
Different Thickness

The experimental investigation on the effects of granular fill and geogrid reinforced granular fill on the behaviour of the static liquefaction potential of the subsoil is reported in this study. A series of plate load test were carried out with different thickness of the granular fill, number of geogrid layers, and size/dimension of the footing. The test results were presented in terms of bearing capacity and subgrade modulus for the settlement ofδ10,δ15, andδ20. The experimental results revealed that the introduction of granular fill significantly increases the bearing capacity and effectively control the settlement behaviour of the footing. The introduction of geogrid in granular fill enhanced the Percentage of Control in Settlement and Bearing Capacity Ratio by a maximum of 328.54% and 203.41%, respectively. The introduction of geogrid in granular fill interrupts the failure zone of the granular fill and enhances the subgrade modulus of the footing by a maximum of 255.55%; in addition subgrade modulus of the footing was increased with an increase in the number of geogrid layers. Based on the test results it is suggested that the footing with large size has beneficial improvement on the reinforced granular fill.

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