Wave Energy Absorption Characteristics of Circular Air-Chamber for Use of Light Beacon Fixed on Sunken Rock

Author(s):  
R. Inoue ◽  
M. Iwai ◽  
M. Yahagi ◽  
T. Yamazaki
1985 ◽  
Vol 12 (6) ◽  
pp. 554-555 ◽  
Author(s):  
Reisaku Inoue ◽  
Masami Iwai ◽  
Masaru Yahagi ◽  
Tetsuo Yamazaki

Author(s):  
Tomoki Ikoma ◽  
Koichi Masuda ◽  
Hisaaki Maeda ◽  
Chang-Kyu Rheem

A pontoon type very large floating structure has elastic deformations in ocean waves. The deformation is larger than that of a semi-submergible type one. Thus, a pontoon type one will be installed to tranquil shallow water field enclosed by breakwaters. Moreover, a semi-submergible one will be applicable to development at offshore field. The authors has developed a pontoon type VLFS with an OWC (oscillating water column) type wave energy absorption system. This can be install to offshore field being deep water relatively. Such VLFS can reduce not only the elastic deformation but also the wave drifting forces. However, it is very difficult to reduce the wave drifting forces effectively because an effect of the reduction depends on the wave energy absorption. Therefore, the authors propose an air supported type VLFS. This idea has been already proposed. However, it wasn’t handled a flexible structure. Such an air-supported structure makes to transmit many waves. Therefore, the wave drifting forces may not increase. In addition, the elastic deformation may decrease because pressure distribution due to the incident waves becomes constant at the bottom of the structure, i.e. the pressure is constant in a same air chamber. We develop the program code for the analysis of the hydrodynamic forces on the VLFS with the air cushion. The potential flow theory is applied and the pressure distribution method is used to the analysis of the wave pressures. The zero-draft is assumed in this method. The pressure and volume change of the air cushion are linearized. In this paper, basic characteristics of the elastic deformations of the air-supported flexible floating structures are investigated. We confirm the effectiveness, and discuss behaviors of the water waves in air chamber areas.


1981 ◽  
Vol 104 ◽  
pp. 159-187 ◽  
Author(s):  
M. J. Simon

A cylindrical duct absorbing energy from incident surface waves is considered. The asymptotic properties of the scattering and radiation potentials are determined, to yield the hydrodynamic quantities on which the energy absorption characteristics of the duct can be shown to depend. It is shown that it is possible to tune the resonant response of the duct to absorb the maximum theoretical energy at a given frequency. Curves are presented showing the variation of energy absorption and the amplitude of the duct response with frequency for various depths of submergence and various tuning frequencies.


Author(s):  
Shi Hu ◽  
Huaming Tang ◽  
Shenyao Han

AbstractIn this paper, polyvinyl chloride (PVC) coarse aggregate with different mixing contents is used to solve the problems of plastic pollution, low energy absorption capacity and poor damage integrity, which provides an important reference for PVC plastic concrete used in the initial support structures of highway tunnels and coal mine roadway. At the same time, the energy absorption characteristics and their relationship under different impact loads are studied, which provides an important reference for predicting the energy absorption characteristics of concrete under other PVC aggregate content or higher impact speed. This study replaced natural coarse aggregate in concrete with different contents and equal volume of well-graded flaky PVC particles obtained by crushing PVC soft board. Also, slump, compression, and splitting strength tests, a free falling low-speed impact test of steel balls and a high-speed impact compression test of split Hopkinson pressure bar (SHPB) were carried out. Results demonstrate that the static and dynamic compressive strength decreases substantially, and the elastic modulus and slump decrease slowly with the increase of the mixing amount of PVC aggregate (0–30%). However, the energy absorption rate under low-speed impact and the specific energy absorption per MPa under high-speed impact increase obviously, indicating that the energy absorption capacity is significantly enhanced. Regardless of the mixing amount of PVC aggregate, greater strain rate can significantly enhance the dynamic compressive strength and the specific energy absorption per MPa. After the uniaxial compression test or the SHPB impact test, the relative integrity of the specimen is positively correlated with the mixing amount of PVC aggregate. In addition, the specimens are seriously damaged with the increase of the impact strain rate. When the PVC aggregate content is 20%, the compressive strength and splitting strength of concrete are 33.8 MPa and 3.26 MPa, respectively, the slump is 165 mm, the energy absorption rate under low-speed impact is 89.5%, the dynamic compressive strength under 0.65 Mpa impact air pressure is 58.77 mpa, and the specific energy absorption value per MPa is 13.33, which meets the requirements of shotcrete used in tunnel, roadway support and other impact loads. There is a linear relationship between the energy absorption characteristics under low-speed impact and high-speed impact. The greater the impact pressure, the larger the slope of the fitting straight line. The slope and intercept of the fitting line also show a good linear relationship with the increase of impact pressure. The conclusions can be used to predict the energy absorption characteristics under different PVC aggregate content or higher-speed impact pressure, which can provide important reference for safer, more economical, and environmental protection engineering structure design.


2010 ◽  
Vol 48 (6) ◽  
pp. 379-390 ◽  
Author(s):  
S. Salehghaffari ◽  
M. Tajdari ◽  
M. Panahi ◽  
F. Mokhtarnezhad

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