scholarly journals PERFORMANCE OF CONCRETE PONTOON FLOATING BREAKWATER WITH DOUBLE CONFIGURATION

2020 ◽  
Vol 11 (2) ◽  
pp. 83-92
Author(s):  
Irham Adrie Hakiki ◽  
Leo Eliasta Sembiring

Development of floating breakwater are increasing along with the rising interest of floating infrastructure. One of the applications is floating breakwater using concrete pontoon. Large and rigid structure are possible to construct with the usage of concrete. However, it still limited with the available construction and transportation method to handle such a large structure. Double configurations of floating breakwater proposed to increase the structure’s performance with the size limitation. The breakwater performance tested with physical model in laboratory by comparing performance of single pontoon with double pontoon for various structure spacing. Pontoon size are 1.2 m in length, 0.3 m in width, and 0.15 m in height and tested with many combination of irregular waves and for double configurations model, the spacing of 30 cm, 60 cm, and 90 cm are used. The structure works optimal in low range harmonic period. Performance of single configuration are in the range of Kt 0.6 up to 0.97, transmission increased along with the waves period. The Kt value of double configuration are around 0.45 up to 0.8. Performance of double configuration determined by ratio of structure spacing with wavelength. Larger ratio resulted a better performance in condition where the spacing did not exceed 0.65 length of wavelength.

2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Irham Adrie Hakiki ◽  
Vilda Ariviana ◽  
Ika Nur Afifah ◽  
Leo Eliasta Sembiring

Experimental Station for Coastal  developed a pilot project of modular concrete floating structure that served as a quay at Kalibaru in North Jakarta. The structure guided by piles and placed in front of Jakarta Coastal Dyke which is a vertical wall structure. From evaluating the structure performance, it is found that the strength of the pile is an important factor for service life of the structure. To provide this, a physical model test of the floating pontoon module guided by piles was conducted at the Laboratory of Balai Litbang Pantai. The model used to determine the behavior of the structure and loads that must be hold by the pile as a seakeeping mechanism. It is done by measuring force acting on piles that caused by pontoon impact by using load cells. The pontoon loaded by regular and irregular waves. From the tests result, the recorded forces has an impuls pattern which have maximum value of 112.67 N. The load that occurs on the pile was not spread evenly on the four piles that hold the floating module. The disrepancy are around 2 – 40%.   The forces acting on piles depends on the ponton distance to the vertical wall. The forces increases along with the increases of relative distances of structure to vertical wall  to the wavelength. The presence of vertical vall caused this increase because it amplify the waves acting on the structure. The amplification effect are the greatest when the structure distrance from the wall is the multiplication factor of halves of wavelength.Keywords : physical model test, pontoon, floating quay, pile guide, impact force


2021 ◽  
Vol 9 (4) ◽  
pp. 388
Author(s):  
Huu Phu Nguyen ◽  
Jeong Cheol Park ◽  
Mengmeng Han ◽  
Chien Ming Wang ◽  
Nagi Abdussamie ◽  
...  

Wave attenuation performance is the prime consideration when designing any floating breakwater. For a 2D hydrodynamic analysis of a floating breakwater, the wave attenuation performance is evaluated by the transmission coefficient, which is defined as the ratio between the transmitted wave height and the incident wave height. For a 3D breakwater, some researchers still adopted this evaluation approach with the transmitted wave height taken at a surface point, while others used the mean transmission coefficient within a surface area. This paper aims to first examine the rationality of these two evaluation approaches via verified numerical simulations of 3D heave-only floating breakwaters in regular and irregular waves. A new index—a representative transmission coefficient—is then presented for one to easily compare the wave attenuation performances of different 3D floating breakwater designs.


2012 ◽  
Vol 1 (33) ◽  
pp. 5 ◽  
Author(s):  
Hernan Fernandez ◽  
Gregorio Iglesias ◽  
Rodrigo Carballo ◽  
Alberte Castro ◽  
Marcos Sánchez ◽  
...  

The development of efficient, reliable Wave Energy Converters (WECs) is a prerequisite for wave energy to become a commercially viable energy source. Intensive research is currently under way on a number of WECs, among which WaveCat©—a new WEC recently patented by the University of Santiago de Compostela. In this sense, this paper describes the WaveCat concept and its ongoing development and optimization. WaveCat is a floating WEC intended for operation in intermediate water depths (50–100 m). Like a catamaran, it consists of two hulls—from which it derives its name. The difference with a conventional catamaran is that the hulls are not parallel but convergent; they are joined at the stern, forming a wedge in plan view. Physical model tests of a 1:30 model were conducted in a wave tank using both regular and irregular waves. In addition to the waves and overtopping rates, the model displacements were monitored using a non-intrusive system. The results of the physical model tests will be used to validate the 3D numerical model, which in turn will be used to optimize the design of WaveCat for best performance under a given set of wave conditions.


2021 ◽  
Author(s):  
Chien Ming Wang ◽  
Huu Phu Nguyen ◽  
Jeong Cheol Park ◽  
Mengmeng Han ◽  
Nagi abdussamie ◽  
...  

<p>Floating breakwaters have been used to protect shorelines, marinas, very large floating structures, dockyards, fish farms, harbours and ports from harsh wave environments. A floating breakwater outperforms its bottom-founded counterpart with respect to its environmental friendliness, cost-effectiveness in relatively deep waters or soft seabed conditions, flexibility for expansion and downsizing and its mobility to be towed away. The effectiveness of a floating breakwater design is assessed by its wave attenuation performance that is measured by the wave transmission coefficient (i.e., the ratio of the transmitted wave height to the incident wave height or the ratio of the transmitted wave energy to the incident wave energy). In some current design guidelines for floating breakwaters, the transmission coefficient is estimated based on the assumption that the realistic ocean waves may be represented by regular waves that are characterized by the significant wave period and wave height of the wave spectrum. There is no doubt that the use of regular waves is simple for practicing engineers designing floating breakwaters. However, the validity and accuracy of using regular waves in the evaluation of wave attenuation performance of floating breakwaters have not been thoroughly discussed in the open literature. This study examines the wave transmission coefficients of floating breakwaters by performing hydrodynamic analysis of some large floating breakwaters in ocean waves modelled as regular waves as well as irregular waves described by a wave spectrum such as the Bretschneider spectrum. The formulation of the governing fluid motion and boundary conditions are based on classical linear hydrodynamic theory. The floating breakwater is assumed to take the shape of a long rectangular box modelled by the Mindlin thick plate theory. The finite element – boundary element method was employed to solve the fluid-structure interaction problem. By considering heave-only floating box-type breakwaters of 200m and 500m in length, it is found that the transmission coefficients obtained by using the regular wave model may be smaller (or larger) than that obtained by using the irregular wave model by up to 55% (or 40%). These significant differences in the transmission coefficient estimated by using regular and irregular waves indicate that simplifying assumption of realistic ocean waves as regular waves leads to significant over/underprediction of wave attenuation performance of floating breakwaters. Thus, when designing floating breakwaters, the ocean waves have to be treated as irregular waves modelled by a wave spectrum that best describes the wave condition at the site. This conclusion is expected to motivate a revision of design guidelines for floating breakwaters for better prediction of wave attenuation performance. Also, it is expected to affect how one carries out experiments on floating breakwaters in a wave basin to measure the wave transmission coefficients.</p>


2003 ◽  
Vol 125 (2) ◽  
pp. 94-102 ◽  
Author(s):  
Svein Helge Gjøsund

It has proven difficult to describe the kinematics in irregular waves satisfactorily, in particular for the surface zone in broad-banded waves. A Lagrangian approach offers distinct advantages in this respect, eliminating the need for extrapolation of solutions or “stretching” of coordinates. This paper presents a model of irregular waves based on superposition of linear Lagrangian wave components, using an iterative method to obtain the Eulerian solution. This approach yields theoretically consistent results everywhere in the waves, and comparisons with wave flume measurements show good agreement. Also, the linear Lagrangian model includes wave interactions that would be nonlinear in an Eulerian formulation.


Author(s):  
Pengyao Yu ◽  
Guoqing Feng ◽  
Huilong Ren ◽  
Xiaodong Zhao

When the ship navigates in the sea, the dynamic deformation of the ship hull will be induced by the waves. The relative large deformation of the ship hull induced by the waves may affect the operation of some certain equipment. In order to keep the equipment operating normally, the influence of the ship deformation should be evaluated. The method for the calculation and analysis of the ship deformation is discussed here. The wave loads of the ship in unit regular wave amplitude are calculated based on 3-D linear potential flow theory. The sea pressure and inertial force of the ship are obtained and applied to the global finite element model of the ship. Under the quasi-static assumption, the structural deformation response in unit regular wave amplitude is calculated with the use of finite element analysis. Then, the amplitude frequency response of the relative deformation between two arbitrary positions in the hull is achieved. The history of the deformation can be obtained based on the simulation of deformation response in irregular waves or the modal superposition method. With the help of spectral analysis method, the spectrum of the relative deformation between two arbitrary positions in the hull may be obtained. The statistical analysis of ship hull deformation in the short-term sea state is realized. Considering the critical value of ship deformation, the reliability analysis method is adopted to assess the ability of hull to resist the deformation.


Author(s):  
Anne Katrine Bratland ◽  
Ragnvald Bo̸rresen ◽  
Per Ivar Barth Berntsen

Wave-current interaction refers to the interaction between surface gravity waves and ocean current flow. This interaction implies an exchange of energy, i.e. both the waves and the current are affected. The present paper describes the calculation of wave elevations in higher order unidirectional, irregular waves with a uniform current in deep water. Results for regular waves are compared with those obtained for Stokes second and third order waves with uniform current according to the method described by Fenton [1]. The results for higher order wave elevations in irregular waves have been compared with waves and current generated in a model test basin and reasonable agreement has been found.


Author(s):  
Aldric Baquet ◽  
Hyunchul Jang ◽  
Ho-Joon Lim ◽  
Johyun Kyoung ◽  
Nicolas Tcherniguin ◽  
...  

Abstract Following the successful application of CFD-based Numerical Wave Basin (NWB) to GBS, TLP and Semisubmersible platforms [1–4], the same methodology has been applied to simulate FPSO hull motion responses to irregular waves. It has been found that the NWB modeling practices developed for the other floater types must be modified for application to an FPSO. This paper describes how the NWB modeling practices have been improved, and then compares results from NWB simulations with those from physical model testing.


Author(s):  
Vengatesan Venugopal ◽  
Stefan Zlatev

A new concept floating breakwater was developed and tested to evaluate its hydrodynamic performance in this paper. This innovative floating breakwater has a rocking body shape which could also be used as a wave power device. A scale model was tested in a wave flume under regular and irregular wave conditions for various combinations of wave frequencies and wave heights. The breakwater has been tested for three immersion depths of 0.05 m, 0.09 m and 0.13 m from still water level. The measured transmitted and reflected waves were used to evaluate the coefficients of transmission (CT), reflection (CR) and dissipation (CL). The results illustrated that the breakwater model performed at its best when submerged at 0.13m, as this immersion depth produced lower coefficients of transmission (CT), lower reflection coefficients (CR) and higher energy dissipation (CL) coefficients. The comparison between regular and irregular waves produced similar ranges of transmission, reflection and energy coefficients.


2017 ◽  
Vol 372 ◽  
pp. 132-141
Author(s):  
Liliana Pinheiro ◽  
Joana Simão ◽  
João Alfredo Santos ◽  
Conceição Juana Fortes

A set of physical model tests was run in to characterize the ship’s response to different wave conditions going from frequently-occurring conditions up to extreme ones. Several wave heights, periods and directions were generated. The waves around the ship were measured with probes and the movements of the ship were measured with a fiber-optic gyrocompass. Transfer functions are established and compared with numerical ones obtained with the WAMIT model.


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