scholarly journals PHYSICAL AND NUMERICAL MODELLING OF THE FLOW STRUCTURE BEHIND STRUCTURE IN TSUNAMI-LIKE FLOW

2018 ◽  
pp. 17
Author(s):  
Hidenori Ishii ◽  
Tomoya Shibayama ◽  
Jacob Stolles
Keyword(s):  
Wave Force ◽  
Flow Fields ◽  
Shielding Effect ◽  
Structure Stability ◽  
Wave Forces ◽  
Coastal Structures ◽  
Three Dimensional Model ◽  
Vertical Column ◽  
Measured Velocity ◽  
Plane Flow

Coastal structures are expected to play a role as evacuation buildings. Numerous studies have been examined tsunami-induced wave force acting on an inland building (Shigihara et al., 2009; Arimitsu et al., 2014). In addition, coastal structures have the potential to obstruct inundating tsunami waves, protecting structure further from the coastline. Hydraulic experiments and numerical calculations on shielding effect are being carried out. Alternatively, the vortices from these structures can result in significant scour downstream, influencing downstream structure stability. In the 2011 Tohoku Region Pacific Offshore Earthquake, many cases were reported that the structure was scrubbed and the structure fallen down. Skakiyama et al. (2007) and Sakakiyma et al. (2008) pointed out that the standing vortex generated around the structure winds sand and causes scouring. Therefore, understanding the vortices generated around the structure is also important in predicting the scouring phenomenon. As such, the flow properties around coastal structures must be considered and acknowledged within the design process. However, there are a few studies focusing on the flow fields behind structure.Arnason et al. (2009) measured velocity fields of dam-break flow around/in the wake of a vertical column. Wei et al. (2015) reproduced the experiment performed using SPH. However, in the experiment, vortexes are not considered and the influence of the existence of structures on the surroundings has not been sufficiently considered. Therefore, in this study, the flow fields of a tsunami-like wave around structures were examined through hydraulic experiments. This experiment was performed to clarify the local vortex structure behind structures by measuring the plane flow velocity field. Also, the effect of obstructing protecting the land side structure is assessed by measuring the wave force behind structures. Furthermore, a three-dimensional model (OpenFOAM) was used to further analyze the flow, focusing on water-level and wave forces behind the structure.

The Concept of the Optimum Alignment of Discharge Pipelines Due to the Minimization of the Wave Forces

1992 ◽  
Vol 25 (9) ◽  
pp. 211-216
Author(s):  
A. Akyarli ◽  
Y. Arisoy
Keyword(s):  
Wave Height ◽  
Wave Force ◽  
Wave Forces ◽  
Wave Direction ◽  
Incoming Wave ◽  
Pipeline Route ◽  
Optimum Alignment ◽  
The Cost ◽  
Resultant Wave

As the wave forces are the function of the wave height, period and the angle between the incoming wave direction and the axis of the discharge pipeline, the resultant wave force is directly related to the alignment of the pipeline. In this paper, a method is explained to determine an optimum pipeline route for which the resultant wave force becomes minimum and hence, the cost of the constructive measures may decrease. Also, the application of this method is submitted through a case study.

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 WAVE ACTION ON LARGE OFF-SHORE STRUCTURES

1976 ◽  
Vol 1 (15) ◽  
pp. 129 ◽  
Author(s):  
C.J. Apelt ◽  
A. Macknight
Keyword(s):  
Numerical Methods ◽  
Water Surface ◽  
Theoretical Method ◽  
Wave Force ◽  
Wave Action ◽  
Tidal Range ◽  
Scale Model ◽  
Wave Forces ◽  
Accurate Calculation ◽  
Scour Protection

The paper describes investigations carried out in order to design for the wave action, both wave force and scour, on large off-shore berthing structures sited approximately 1.3 miles (2.1 km) off-shore near Hay Point, North Queensland, in 56 feet (17 m) of water at low tide, the tidal range being 20 feet (6 m). The region is a cyclone area and the structures must be capable of withstanding attack from maximum predicted waves with period of 8.25 seconds and amplitude of 24 feet (7.3 m). The main units in the berthing structures are concrete caissons sunk on to the ocean bed and the largest of these have plan dimensions of approximately 150 feet (46.7 m) by 135 feet (41.4 m) with four columns approximately 40 feet (12.2 m) square projecting through the water surface. No theoretical method available at the time of the investigation was capable of accurate calculation of wave forces on these structures. A scale model was tested to obtain wave forces and the paper compares results from the model with those of numerical methods and discusses the application of the results to the design functions. Scour effects were also modelled and the results used as the basis for design of scour protection.

Experimental Study of Wave Force Distribution on a Monopile Structure

2018 ◽  
Author(s):  
Malene H. Vested ◽  
Stefan Carstensen ◽  
Erik Damgaard Christensen
Keyword(s):  
Experimental Studies ◽  
Cost Effective ◽  
Wave Force ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Force Distribution ◽  
Wave Forces ◽  
Total Force ◽  
Wave Flume ◽  
Effective Manner

As the demand for offshore wind energy continues to grow, the strive to understand the wave forces acting on the substructure of the wind turbines continues. In regard to wind turbine design, it is vital to consider not only the total wave force, but also the local wave forces. Local forces are particularly important for the design of secondary structures as e.g. mooring platforms. Typically, however, experimental studies mainly concern total forces or idealized local forces. We present here a rather simple way to measure local forces along a model monopile. The study is conducted in a wave flume of 28 m in length, in which waves are generated by a piston-type wave maker at a water depth of 0.515 m and shoal onto a bed of slope 1:25. A model monopile is installed and subjected to forcing from a series of both regular and irregular waves. In the experimental set-up, the model monopile is fixed at the bottom and the top and consists of seven independent cylindrical sections. The cylindrical sections are connected by force transducers which measure local shear, and so the associated local forces may be determined. The measured local forces are compared to the force distribution given by Morisons equation combined with linear theory and Wheeler stretching, which is a force estimate commonly used in the industry. This study shows that the total force is rather well captured by Morison’s equation. The force distribution estimated from Morison’s equation, however, shows larger discrepancies from the measured forces. This encourages for further measurements. In this study, we show that it is possible to measure force distribution on a model monopile in a simple and cost-effective manner. The aim is here to demonstrate the method and we will later present a larger body of work associated with the outcome of the measurements.

scholarly journals Wave interaction with Floating platform of different shapes and supports using BEM approach

2017 ◽  
Vol 14 (2) ◽  
pp. 115-133
Author(s):  
Anoop I. Shirkol ◽  
Nasar Thuvanismail
Keyword(s):  
Numerical Model ◽  
Elastic Plate ◽  
Wave Interaction ◽  
Wave Force ◽  
Ocean Waves ◽  
Wave Forces ◽  
Thin Elastic Plate ◽  
Floating Platform ◽  
Floating Elastic Plate ◽  
Different Shapes

Wave interaction with a floating thin elastic plate which can be used as floating platform is analyzed using Boundary Element Method (BEM) for different shapes such as rectangular, circular and triangular. Different support conditions are considered and the performance of the floating platform under the action of ocean waves is explored. The study is performed under the assumption of linearized water wave theory and the floating elastic plate is modelled based on the Euler-Bernoulli beam theory. Using Galerkin’s approach, a numerical model has been developed and the hydrodynamic loading on the floating elastic plate of shallow draft (thickness) is investigated. The wave forces are generated by the numerical model for the analysis of the floating plate. The resulting bending moment and optimal deflection due to encountering wave force is analysed. The present study will be helpful in design and analysis of the large floating platform in ocean waves.

Numerical Modelling of Breaking Wave Interaction With a Group of Four Vertical Slender Cylinders in Square Arrangements

2016 ◽  
Author(s):  
Mayilvahanan Alagan Chella ◽  
Hans Bihs ◽  
Arun Kamath ◽  
Dag Myrhaug ◽  
Øivind Asgeir Arnsten
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Model ◽  
Numerical Modelling ◽  
Wave Interaction ◽  
Wave Force ◽  
Wave Forces ◽  
Breaking Wave ◽  
Square Configuration ◽  
Breaking Wave Forces

The main purpose of the study is to investigate the breaking wave interaction with a group of four circular cylinders. The physical process of wave breaking involves many parameters and an accurate numerical modelling of breaking waves and the interaction with a structure remain a challenge. In the present study, the open-source (Computational Fluid Dynamics) CFD model REEF3D is used to simulate the breaking wave interaction with the multiple cylinders. The numerical model is based on the incompressible Reynolds Averaged Navier-Stokes (RANS) equations, the level set method for the free surface and the k–ω model for turbulence. The model uses a 5th-order conservative finite difference WENO scheme for the convective discretization and a 3rd-order Runge-Kutta scheme for time discretization. The numerical model is validated with experimental data of large-scale experiments for the free surface elevation and the breaking wave force on a single cylinder. A good agreement is seen between the numerical results and experimental data. Two different configurations with four cylinders are examined: in-line square configuration and diamond square configuration. The breaking wave forces on each cylinder in the group are computed for the two cases and the results are compared with the breaking wave force on a single isolated cylinder. Further, the study investigates the water surface elevations and the free surface flow features around the cylinders. In general, the cylinders in both configurations experience the maximum forces lower than the maximum force on a single cylinder. The results of the present study show that the interference effects from the neighbouring cylinders in a group strongly influence the kinematics around and the breaking wave forces on them.

Experimental Study on the Wave Loads on Monopile and Jacket Type Support of Offshore Wind Turbines

2018 ◽  
Author(s):  
Jing Zhang ◽  
Qin Liu ◽  
Xing Hua Shi ◽  
C. Guedes Soares
Keyword(s):  
Experimental Study ◽  
Wind Turbine ◽  
Nonlinear Wave ◽  
Wave Force ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Forces ◽  
Wave Loads ◽  
Morison Equation ◽  
Offshore Wind Turbines

As the offshore fixed wind turbine developed, more ones will be installed in the sea field with the depth 15–50 meters. Wave force will be one of the main forces that dominate the design of the wind turbine base, which is calculated using the Morison equation traditionally. This method can predict the wave forces for the small cylinders if the drag and inertia coefficients are obtained accurately. This paper will give a series scaled tests of monopile and jacket type base of the offshore wind turbine in tank to study the nonlinear wave loads.

Second-Order Diffraction Loads on Plural Vertical Cylinder With Arbitrary Cross Sections

1987 ◽  
Vol 109 (4) ◽  
pp. 314-319
Author(s):  
K. Masuda ◽  
W. Kato ◽  
H. Ishizuka
Keyword(s):  
Boundary Value Problem ◽  
Cross Sections ◽  
Present Method ◽  
Boundary Value ◽  
Vertical Cylinder ◽  
Wave Force ◽  
Second Order ◽  
Wave Forces ◽  
Order Diffraction ◽  
Rectangular Cylinders

The purpose of the present study is development of a powerful numerical method for calculating second-order diffraction loads on plural vertical cylinder with arbitrary cross sections. According to the present method, second-order wave force can be obtained from a linear radiation potential without solving second-order boundary value problem. The boundary value problem for the radiation potential is solved with the hybrid boundary element method. The computations for circular and rectangular cylinders were carried out and compared with the experiments. In addition, second-order wave forces on twin circular cylinder are calculated with the present method.

Structural Analysis of a Hybrid Substructure With Multi-Cylinder for 5MW Offshore Wind Turbines

2014 ◽  
Author(s):  
Min-Su Park ◽  
Youn-Ju Jeong ◽  
Young-Jun You
Keyword(s):  
Free Surface ◽  
Structural Analysis ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Expansion Method ◽  
Wave Force ◽  
Offshore Wind ◽  
Wave Forces ◽  
Offshore Wind Turbines ◽  
Scattering Wave

The substructure for offshore wind turbines is strongly influenced by the effect of wave forces as the size of substructure increases. Therefore, it is very important to reduce the wave force acting on substructures. In the present study the hybrid substructure, which is composed of a multi-cylinder having different radius near free surface and a gravity substructure at the bottom of multi-cylinder, is suggested to reduce the wave forces. The fluid domain is divided into two regions to calculate the wave forces acting on the hybrid substructure with multi-cylinder and the scattering wave in each fluid region is expressed by an Eigen-function expansion method. The comparison between the mono pile and the hybrid substructure is made for wave forces. Using the wave forces obtained from this study, the structural analysis of hybrid substructure is carried out through ANSYS mechanical. In order to investigate the resonance between the wind turbine and the hybrid substructure, the modal analysis is also carried out.

EXPERIMENTAL STUDY ON IMPULSIVE FORCE OF DRIFT BODY DUE TO TSUNAMI FLOW

2010 ◽  
Vol 04 (02) ◽  
pp. 127-133 ◽  
Author(s):  
TETSUYA HIRAISHI ◽  
KAZUTO HARUO ◽  
EIJI SAITOH
Keyword(s):  
Wave Force ◽  
Indian Ocean Tsunami ◽  
Vertical Column ◽  
Wave Basin ◽  
The Indian Ocean ◽  
Collision Force ◽  
Under Construction ◽  
Design Earthquake ◽  
A Current ◽  
Experimental Equation

In the Indian Ocean Tsunami, numerous drifting bodies like timbers induced by the strong tsunami flow caused the damage of houses. Such influences by the drifting body due to tsunami are worried especially in the Japanese harbor area where a new offshore runway is under construction using the jacket-type structure. The jacket is composed of vertical piers and oblique supporters with about 1 m diameter and is placed in the sea 20 m deep. In the paper, the impulsive wave force by a drifting timber due to tsunami flows is experimentally studied using a wave basin with a current generator. The target tsunami flow velocity calculated for the design earthquake is 0.9 m/s at the jacket location and the scale in the experiment is 1/10. In the experiments, the maximum total horizontal force acting on a vertical column fixed in a channel was measured and its characteristic was investigated. The collision force was mainly determined in the drifting velocity and timber mass. An experimental equation to evaluate the maximum force was derived and its accuracy was demonstrated.

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