The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Hwunghweng Hwung - One of the best experts on this subject based on the ideXlab platform.
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structural permeability effects on the interaction of a solitary wave and a submerged Breakwater
Coastal Engineering, 2003Co-Authors: Chingjer Huang, Hsing Han Chang, Hwunghweng HwungAbstract:Abstract The unsteady two-dimensional Navier–Stokes equations and Navier–Stokes type model equations for porous flows were solved numerically to simulate the interaction between a solitary wave and a submerged porous Breakwater. The free surface boundary conditions and the interfacial boundary conditions between the water and the porous media are in complete form. A piston-type wavemaker, set-up in the computational domain, generated the incident solitary wave. The accuracy of the numerical model was verified by comparing the numerical results with the experimental data. Having verified the accuracy of the numerical model, the effects of several parameters on the interaction of a solitary wave and a submerged Breakwater were systematically investigated. These parameters include the incident wave height, the aspect ratio of the Breakwater, and the porosity including the impermeable case. The flow fields near the Breakwater are discussed in terms of the velocity vectors, the vortex shedding and the trajectories of the fluid particles. The pressure drag acting on the Breakwater was also calculated. The numerical results reveal that if the Breakwater width is small compared with the effective wave length, the structure permeability has no apparent effect on wave transformation. For wide porous Breakwaters, if the structure porosity is small, the increase in the porosity results in the reduction of the transmission coefficient; otherwise the transmission coefficient increases with porosity.
J. S. Mani - One of the best experts on this subject based on the ideXlab platform.
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Reef Breakwaters for Coastal Protection
2020Co-Authors: A. Chiranjeevi Rambabu, J. S. ManiAbstract:This paper presents results of a numerical modelling study to investigate the performance of impermeable reef Breakwaters for coastal protection. The study aimed to define the effect of depth of submergence, surface width of structure and reef Breakwater spacing on wave transmission characteristics. The results identify an optimum surface width of reefs and optimum spacing between reefs. The solution is written in terms of velocity potential of the waves. The scattered portion of potential is solved numerically based on Green's formulation. The results show that for ds/d>0.625 and Hi/gT2>0.006, the Breakwater is capable of reducing incident waves by about 60%. Results also indicate an optimum width ratio of B/d=0.75. By restricting the effective width ratio of the series of Breakwater to 0.75, studies were conducted to determine the effect of spacing between Breakwaters on the transmission coefficient, suggesting an optimum clear spacing of w/b=2.00.
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Numerical prediction of performance of submerged Breakwaters
Ocean Engineering, 2005Co-Authors: A. Chiranjeevi Rambabu, J. S. ManiAbstract:Abstract The results of a numerical model study on the transmission characteristics of a submerged Breakwater are presented. Study aimed to determine the effect of depth of submergence, crest width, initial wave conditions and material properties on the transmission characteristics of the submerged Breakwater. The results highlight the optimum crest width of the Breakwater and optimum clear spacing between two Breakwaters. A submerged permeable Breakwater with d s / d =0.5, p =0.3 and f =1.0, reduces the transmission coefficient by about 10% than the impermeable Breakwater. The results indicates an optimum width ratio of B / d =0.75 for achieving minimum transmission. By restricting the effective width ratio of the series of Breakwaters to 0.75, studies were conducted to determine the effect of clear spacing between Breakwaters on transmission coefficient, suggesting an optimum clear spacing of w / b =2.00 to obtain K t below 0.6.
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Dynamics of Cage Floating Breakwater
Journal of Offshore Mechanics and Arctic Engineering-transactions of The Asme, 2005Co-Authors: K. Murali, S. S. Amer, J. S. ManiAbstract:Floating Breakwaters have potential applications in protecting minor ports and harbors such as fisheries and recreational harbors, where-in stringent tranquillity requirements are not warranted. In field applications of the existing floating Breakwaters, limitations are imposed due to their large relative width (ratio between Breakwater width and wave length) requirements to achieve desirable tranquillity level. This relative width requirement is greater than 0.3 for the existing floating Breakwaters. To overcome the above drawback associated with the existing system a new configuration for a floating Breakwater is derived, which could yield the desired performance with minimum relative width requirement. The floating Breakwater comprises of two pontoons rigidly connected together and each of the pontoons having a row of cylinders attached beneath, for improved performance characteristics. The laboratory tests were conducted in both regular and random wave flumes to study the dynamic behavior of the Breakwater. Transmission and reflection coefficients, water surface elevations and velocities inside the cage like area provided in between the pontoons, rigid body motions floating Breakwater and mooring forces were studied under regular and random waves and under the regular waves followed by a uniform current. The results proved the suitability of the floating Breakwater to the field conditions even for large wave periods. In addition the variations in water particle kinematics, rigid body motion and mooring forces show nominal magnitudes when compared to the existing systems indicating the rigidness of the Breakwater.
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performance of cage floating Breakwater
Journal of Waterway Port Coastal and Ocean Engineering-asce, 1997Co-Authors: K. Murali, J. S. ManiAbstract:Conventional floating Breakwaters are examined and the feasibility of developing a cage floating Breakwater is explored. Earlier studies on floating Breakwaters reveal that, to achieve a transmission coefficient (\iK\i\dt) less than 0.5, the Breakwater width to wave length ratio (\IW/L\N) should necessarily be greater than 0.4 for most of the configurations. Recent studies on cost-effective floating Breakwaters indicate that by fixing a row of pipes below the floating body, the \IW/L\N requirement can be reduced to 0.15 without any compromise in the performance. This concept has been adopted in developing a new configuration to serve as: (1) a floating Breakwater; and (2) as a possible shallow water cage culture unit. Experiments were conducted to study the performance of the cage floating Breakwater under wave and wave-current environment. The results on transmission and reflection coefficients are presented and compared with those reported in the literature. The variation of water surface oscillations and velocities within the cage, the effect of mooring line stiffness, and initial tension on transmission characteristics are also discussed.
Chingjer Huang - One of the best experts on this subject based on the ideXlab platform.
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structural permeability effects on the interaction of a solitary wave and a submerged Breakwater
Coastal Engineering, 2003Co-Authors: Chingjer Huang, Hsing Han Chang, Hwunghweng HwungAbstract:Abstract The unsteady two-dimensional Navier–Stokes equations and Navier–Stokes type model equations for porous flows were solved numerically to simulate the interaction between a solitary wave and a submerged porous Breakwater. The free surface boundary conditions and the interfacial boundary conditions between the water and the porous media are in complete form. A piston-type wavemaker, set-up in the computational domain, generated the incident solitary wave. The accuracy of the numerical model was verified by comparing the numerical results with the experimental data. Having verified the accuracy of the numerical model, the effects of several parameters on the interaction of a solitary wave and a submerged Breakwater were systematically investigated. These parameters include the incident wave height, the aspect ratio of the Breakwater, and the porosity including the impermeable case. The flow fields near the Breakwater are discussed in terms of the velocity vectors, the vortex shedding and the trajectories of the fluid particles. The pressure drag acting on the Breakwater was also calculated. The numerical results reveal that if the Breakwater width is small compared with the effective wave length, the structure permeability has no apparent effect on wave transformation. For wide porous Breakwaters, if the structure porosity is small, the increase in the porosity results in the reduction of the transmission coefficient; otherwise the transmission coefficient increases with porosity.
Inigo J Losada - One of the best experts on this subject based on the ideXlab platform.
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rans modelling applied to random wave interaction with submerged permeable structures
Coastal Engineering, 2006Co-Authors: Javier L Lara, Nicolas Garcia, Inigo J LosadaAbstract:Abstract This paper is the second part of the work presented by Garcia et al. [Garcia, N., Lara, J.L., Losada, I.J., 2004. 2-D numerical analysis of near-field flow at low-crested Breakwaters. Coastal Engineering 51 (10), 991–1020]. In the mentioned paper, flow conditions at low-crested rubble-mound Breakwaters under regular wave attack were examined, using a combination of measured data of free surface, bottom pressure and fluid velocities from small-scale experiments and numerical results provided by a VOF-type model (COBRAS) based on the Reynolds-Averaged Navier–Stokes (RANS) equations. This paper demonstrates the capability of the COBRAS model to reproduce irregular wave interaction with submerged permeable Breakwaters. Data provided by the numerical model are compared to experimental data of laboratory tests, and the main processes of wave–structure interaction are examined using both experimental and numerical results. The numerical model validation is carried out in two steps. First, the procedure of irregular wave generation is verified to work properly, comparing experimental and numerical data of different cases of irregular wave trains propagating over a flat bottom. Next, the validation of the numerical model for wave interaction with submerged rubble-mound Breakwaters is performed through the simulation of small-scale laboratory tests on different incident wave spectra. Results show that the numerical model adequately reproduces the main aspects of the interaction of random waves with submerged porous Breakwaters, especially the spectral energy decay at the structure and the spectrum broadening past the structure. The simulations give good results in terms of height envelopes, mean level, spectral shape, root-mean-square height for both free surface displacement and dynamic pressure inside the Breakwater. Moreover, large-scale simulations have been conducted, on both regular and irregular incident wave conditions. The overall pattern of the wave interaction with a large-scale submerged Breakwater is adequately reproduced by the numerical model. The processes of wave reflection, shoaling and breaking are correctly captured. The good results achieved at a near prototype scale are promising regarding the use of the numerical model for design purposes.
Jorgen Juhl - One of the best experts on this subject based on the ideXlab platform.
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Berm Breakwater structures
1996Co-Authors: Jorgen JuhlAbstract:The overall objective of the research project on berm Breakwater structures is to arrive at a better design basis, which will bring the design standards of berm Breakwaters up to the level of design standards for other civil engineering structures. This objective will be reached by establishing an understanding of the physics of berm Breakwaters, studies of problems related to practical engineering applications, and studies of threedimensional effects. The research is a combination of theoretical work, physical model testing and numerical modelling. The paper gives an introduction to the berm Breakwater concept followed by a presentation of the main research results obtained within MAST 1. Finally, the research which is carried out as part of the MAST II project on berm Breakwater structures is described, including a brief presentation of the first results.
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Berm Breakwater structures: Berm Breakwater trunk exposed to oblique waves
1996Co-Authors: A. Alikhani, R.g. Tomasicchio, Jorgen JuhlAbstract:The major part of the research on berm Breakwaters has concentrated on the berm reshaping of a trunk section exposed to head-on waves. Recent research included aspects related to individual stone movements under perpendicular wave attack (eg Tomasicchio et al). For a berm Breakwater trunk section consisting of berm stones smaller than a certain size, the stones will continue to move in the wave direction (longshore transport) when the Breakwater is exposed to oblique waves. Only a little research has been made to study the effect of oblique waves on the reshaping and longshore transport of berm Breakwaters (eg Burcharth and Frigaard, and Van der Meer and Veldman). A series of comprehensive model tests and subsequent analyses were carried out with the aim to study the influence of wave obliquity on the reshaping process, on the initiation of longshore transport, and on the longshore transport rate. The model set-up and test programme are described in Juhl et al.
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Berm Breakwater structures: Roundhead stability of berm Breakwaters
1996Co-Authors: Jorgen Juhl, A. Alikhani, Peter Sloth, Renata ArchettiAbstract:For berm Breakwaters as compared with traditional rubble mound Breakwaters, special measures have to be taken for the Breakwater roundhead. If stone displacements occur on a roundhead, the stones will be moved in the wave direction and will loose most of their stabilising effect. The major part of the research on berm Breakwaters has concentrated on the reshaping of the seaward side of the trunk under perpendicular wave attack. Only a little research has been made to study the stability of berm Breakwater roundheads (eg Burcharth and Frigaard, Jensen and Sorensen, and Van der Meer and Veldman). Comprehensive three-dimensional (3D) model tests were carried out to study the reshaping of the roundhead as function of the wave conditions (wave height and wave period) and the angle of wave incidence. The reshaping process and the movements of stones on the berm were analysed based on both profile measurements and observations.
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Berm Breakwater structures: Roundhead stability of berm Breakwaters / Reshaping Breakwater - Longshore transport and recession of the berm
1995Co-Authors: Jorgen Juhl, A. Alikhani, Peter Sloth, Renata ArchettiAbstract:For berm Breakwaters as compared with traditional rubble mound Breakwaters, special measures have to be taken for the Breakwater roundhead. If stone displacements occur on a roundhead, the stones will be moved in the wave direction and will loose most of their stabilising effect. A point of special concern is whether, and under which conditions, a berm Breakwater roundhead will develop in a way that in the long-term will lead to structural failure. The major part of the research on berm Breakwaters has concentrated on the reshaping of the seaward side cif the trunk under perpendicular wave attack. Only a little research has been made to study the stability of berm Breakwater roundheads (eg Burcharth and Frigaard, Jensen and Serensen, and Van der Meer and Veldman). Comprehensive three-dimensional model tests have been carried out to study the reshaping of the roundhead as function of the wave conditions (wave height and wave period) and the angle of wave incidence. The reshaping process and the movements of stones on the berm have been analysed based on both profile measurements and observations.
