Performance Analysis of a Semicircular Free Surface Breakwater

2011 ◽  
Author(s):  
Hee Min Teh ◽  
Vengatesan Venugopal ◽  
Tom Bruce
Keyword(s):  
Free Surface ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Wave Forces ◽  
Front Wall ◽  
Wave Flume ◽  
Horizontal Wave ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
Semicircular Breakwater

In the present study, the hydrodynamic performance of a semicircular free surface breakwater (SCB) has been investigated through a systematic experimental programme. Three semicircular breakwater models were tested: one with impermeable front and rear walls; a second with perforated front wall and impermeable rear wall; and a third with perforated front and rear walls. The models were tested for three submergence depths with reference to the still water level in a wave flume under irregular seas with different significant wave heights and peak periods. The performance of the breakwaters was evaluated in the form of coefficients of transmission (CT), reflection (CR) and energy dissipation (CL). The measured wave modification in front of the structure and in the breakwater’s chamber were quantified and presented in the form of a ratio relative to the incident wave height, respectively. Also, the measured horizontal wave forces acting on the SCB were analysed and reported in a dimensionless form. Empirical equations were then developed using nonlinear multiple regression models to estimate the hydrodynamic characteristics of the SCB models.

scholarly journals HYDRODYNAMIC PERFORMANCE OF A FREE SURFACE SEMICIRCULAR PERFORATED BREAKWATER

2011 ◽  
Vol 1 (32) ◽  
pp. 20 ◽  
Author(s):  
Hee Min Teh ◽  
Vengatesan Venugopal ◽  
Tom Bruce
Keyword(s):  
Free Surface ◽  
Wave Attenuation ◽  
Hydrodynamic Performance ◽  
Wave Transformation ◽  
Hydrodynamic Characteristics ◽  
Wave Forces ◽  
Irregular Wave ◽  
Energy Dissipater ◽  
Horizontal Wave ◽  
Perforated Breakwater

The increasing importance of the sustainability challenge in coastal engineering has led to the development of free surface breakwaters of various configurations. In this study, the hydrodynamic characteristics of a perforated semicircular free surface breakwater (SCB) are investigated for irregular wave conditions. The hydrodynamic performance of the breakwater is evaluated in the form of transmission, reflection and energy dissipation coefficients, which are then presented as a function of the relative submergence depth (D/d) and the relative breakwater width (B/Lp), where D = the depth of immersion, d = the water depth, B = the breakwater width and Lp = the wavelength corresponding to the peak wave period. It is found that the wave attenuation ability of the SCB model improves with the increase of D/d and B/Lp. The SCB performs better as an energy dissipater than as a wave reflector. Based on the analysis of measured data, some empirical equations are proposed to predict the performance of the breakwater under varying submergence depths. The behaviour of wave transformation around and within the breakwater’s chamber is discussed. Also, the measured horizontal wave forces acting on the SCB are reported.

Optimization of Hydraulic Efficiency of a Free Surface Semicircular Breakwater Using Wave Screens

2015 ◽  
Author(s):  
Hee Min Teh ◽  
Vengatesan Venugopal
Keyword(s):  
Free Surface ◽  
Wave Climate ◽  
Wave Transmission ◽  
Hydrodynamic Performance ◽  
Wave Transformation ◽  
Random Waves ◽  
Wave Flume ◽  
Wave Measurements ◽  
Test Models ◽  
Semicircular Breakwater

A free surface semicircular breakwater (SCB) with rectangular perforations has been developed to serve as a wave defence structure. Hydrodynamic performance of the breakwaters of various perforations has been thoroughly investigated through wave measurements in a wave flume under random waves. The SCBs were experimentally confirmed to be good anti-reflection wave structures; however, the level of wave transmission at the leeside of the SCBs was rather high particularly when immersed in limited depth and confronted by waves of longer period. This study aims at optimizing the hydraulic characteristics of the SCB by extending its draft by means of wave screens. Three test configurations have been identified in this study, namely (1) the SCB with front screen, (2) the SCB with rear screen, and (3) the SCB with double screens. For each wave screen, three porosities (i.e. 25, 40 and 50%) have been considered in the experiments. The models of shallow immersion depths have been tested in random waves of different characteristics in a wave flume. Wave transformation at different locations upstream and downstream of the test models has been recorded by wave probes. The hydraulic performance of the breakwater are quantified by the coefficients of wave transmission, reflection and energy dissipation, and the wave climate in the vicinity of the breakwater are presented in the form of a ratio relative to the incident wave height. The optimum design of SCB supplemented by truncated wave screen(s) is proposed at the end of the study.

scholarly journals WAVE FORCES ON SQUARE CAISSONS

1976 ◽  
Vol 1 (15) ◽  
pp. 132 ◽  
Author(s):  
G.R. Mogridge ◽  
W.W. Jamieson
Keyword(s):  
Experimental Data ◽  
Theoretical Method ◽  
Wave Forces ◽  
Simple Method ◽  
Method Of Calculation ◽  
Wave Flume ◽  
Wide Range ◽  
Wave Heights ◽  
And Storage ◽  
Water Depths

The forces and overturning moments exerted by waves on large vertical square-section caissons have been measured in the laboratory. Each model caisson extended from the bottom of a wave flume through the water surface and was oriented either with one side perpendicular to the direction of wave propagation or turned through an angle of forty-five degrees to this position. For a given orientation, each model was tested for a range of wave heights (up to the point of breaking) for various wave periods and water depths. A digital computer was used for the acquisition, processing, plotting and storage of the experimental data. In addition to the experimental work, an approximate theoretical method is presented which allows the wave loadings on a square caisson to be estimated by means of a simple desk calculation. The experimental data shows that this simple method of calculation is reasonably accurate over a wide range of wave conditions and caisson sizes.

Hydrodynamic Performance of a Novel Free Surface Pitching Breakwater

2014 ◽  
Author(s):  
Vengatesan Venugopal ◽  
Stefan Zlatev
Keyword(s):  
Body Shape ◽  
Hydrodynamic Performance ◽  
Irregular Waves ◽  
Scale Model ◽  
Reflected Waves ◽  
Irregular Wave ◽  
Wave Flume ◽  
Floating Breakwater ◽  
Wave Heights ◽  
Transmission Ct

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.

scholarly journals PERFORMANCE ANALYSIS OF COMPOSITE SEMICIRCULAR BREAKWATERS OF DIFFERENT CONFIGURATIONS AND POROSITIES

2012 ◽  
Vol 1 (33) ◽  
pp. 38 ◽  
Author(s):  
Hee Min Teh ◽  
Vengatesan Venugopal ◽  
Tom Bruce
Keyword(s):  
Free Surface ◽  
Energy Dissipation ◽  
Performance Analysis ◽  
Physical Modelling ◽  
High Energy ◽  
Immersion Depth ◽  
Irregular Waves ◽  
Hydrodynamic Characteristics ◽  
Semicircular Breakwater ◽  
High Energy Dissipation

The perforated free surface semicircular breakwater developed by Teh et al. (2010) was experimentally proven to be an effective anti-reflection structure with high energy dissipation ability. However, the performance characteristics of the breakwater deteriorated with a decrease in the immersion depth and an increase in wavelength. To enhance the performance of the breakwater with limited immersion depth, wave screens of different configurations and porosities were introduced below the free surface semicircular caisson. The hydrodynamic characteristics of these composite breakwaters were investigated in irregular waves using physical modelling. Comparisons of the experimental results showed that the semicircular caisson with a double screen of 25% porosity was a better breakwater configuration compared to that with a single screen. The extension of wave screen was also found to be particularly helpful in attenuating longer waves.

Performance Analysis of a Semicircular Free Surface Ocean Structure under the Different Water Depths

2011 ◽  
Vol 90-93 ◽  
pp. 2782-2789
Author(s):  
Gang Jun Zhai ◽  
Zhe Ma ◽  
Hee Min Teh ◽  
Vengatesan Venugopal
Keyword(s):  
Free Surface ◽  
Wave Height ◽  
Incident Wave ◽  
Wave Attenuation ◽  
Hydrodynamic Characteristics ◽  
Irregular Wave ◽  
Surface Ocean ◽  
Semicircular Breakwater ◽  
Water Depths ◽  
Structure Width

The increasing importance of the sustainability challenge in o engineering has led to the development of free surface ocean structure of various configurations. In this study, the hydrodynamic characteristics of a perforated free surface, semicircular breakwater (SCB) are investigated for irregular wave conditions under the different water depths. The performance of the breakwaters was evaluated in the form of coefficients of transmission (CT), reflection (CR) and energy dissipation (CL). The measured wave modification in front of the structure and in the structure’s chamber were quantified and presented in the form of a ratio relative to the incident wave height, respectively, which are then presented as a function of the relative immersion depth (D/d) and the relative structure width (B/Lp), where D = the depth of immersion, d = the water depth, B = the structure width and Lp = the wavelength corresponding to the peak wave period. The measured wave modification in front of the structure and in the breakwater’s chamber were quantified and presented in the form of a ratio relative to the incident wave height, respectively. It is found that the wave attenuation ability of the SCB model improves with the increase of D/d and B/Lp. The SCB performs better as an energy dissipater than as a wave reflector.

Regular Wave Experiments for Twin Circular Submerged Floating Tunnel Tethered to Sea Bottom

2017 ◽  
Author(s):  
Sang-Ho Oh ◽  
Woo Sun Park
Keyword(s):  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Two Dimensional ◽  
Wave Loading ◽  
Regular Waves ◽  
Wave Flume ◽  
Sea Bottom ◽  
Physical Experiments ◽  
Tensile Forces ◽  
Submerged Floating Tunnel

Assessment of hydrodynamic performance of submerged floating tunnel (SFT) under wave loading is one of important factor in the design of the structure. In this study, physical experiments were conducted in a two-dimensional wave flume to investigate hydrodynamic characteristics of a twin circular SFT model under the action of regular waves having different heights and periods. Five different configurations of the twin SFT model was tested in the experiment. The experimental results showed that the three-degree motions of the twin SFT and the associated tensile forces on the tension legs greatly vary with the configurations of the model. It was found that the CD0 configurations are most adequate for satisfactorily restricting the horizontal and vertical motions of the SFT model.

scholarly journals Influence of the Perforated Rate on the Wave Attenuation Performance of Perforated Caisson Set on a Rubble Bed

2021 ◽  
Author(s):  
Peihong Zhao ◽  
Dapeng Sun ◽  
Hao Wu
Keyword(s):  
Reflection Coefficient ◽  
Wave Attenuation ◽  
Wave Force ◽  
Wave Forces ◽  
Front Wall ◽  
Minimum Value ◽  
Physical Experiments ◽  
Horizontal Wave ◽  
Horizontal Wave Force ◽  
Perforated Caisson

A Jarlan-type perforated caisson (JTPC) was an important form of structure in offshore and coastal engineering and its wave attenuation performance was greatly affected by μ (the perforated rate). In the present research, a numerical model based on VARANS equations was tested by comparing the simulation results with physical experiments and then adopted to study the effect of a larger range of μ on wave attenuation performance which included both the horizontal wave forces and the reflection coefficients. Conclusions were drawn that the total horizontal wave force and the reflection coefficient both tended to decrease and then increase with increasing μ; when the reflection coefficient reached its minimum value as about μ=0.2, the wave force at the seaward side of the perforated front wall tended to be equal to that at the solid rear wall; the total horizontal wave force reached its minimum value as about μ=0.3.

scholarly journals Influence of Wave-Absorbing Chamber Width on the Wave Attenuation Performance of Perforated Caisson Sitting on Rubble-Mound Foundation

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Peihong Zhao ◽  
Dapeng Sun ◽  
Hao Wu
Keyword(s):  
Numerical Model ◽  
Wave Attenuation ◽  
Wave Force ◽  
Reflection Coefficients ◽  
Wave Forces ◽  
Front Wall ◽  
Horizontal Wave ◽  
Rubble Mound ◽  
Horizontal Wave Force ◽  
Perforated Caisson

A Jarlan-type perforated caisson consisted of a perforated front wall, a solid rear wall, and a wave-absorbing chamber between them. The wave-absorbing chamber was the main feature of the perforated caisson, and its width had a great effect on wave attenuation performance. In this study, a larger range of the wave-absorbing chamber width was observed in model experiments to investigate the effect on wave attenuation performance including the reflection coefficients and the horizontal wave forces of a perforated caisson sitting on a rubble-mound foundation. A resistance-type porosity numerical model based on the volume-averaged Reynolds-averaged Navier–Stokes (VARANS) equations was validated by comparing the present results with those of previously reported and present experiments. The validated numerical model was then used for extended research. It was found that the reflection coefficients, the total horizontal wave force, and its components all tended to oscillate in a decrease ⟶ increase ⟶ decrease manner with increasing the wave-absorbing chamber width. The reflection coefficients and wave forces acting on both sides of the perforated front wall were found to be synchronized regardless of perforation ratio or the rubble-mound foundation height.

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