The interaction of water waves with a tensioned, unstretchable, vertical flexible membrane extended to the seabed is solved in the context of two-dimensional linear wave theory. First, analytic solutions are obtained based on the eigenfunction expansion of the velocity potential in two fluid domains and a continuous tensioned-string dynamic model. In contrast to the rigid-body hydrodynamics, the velocity potentials and membrane equation of motions are obtained simultaneously, since the membrane boundary condition is not known in advance. Second, a boundary element program based on a discrete membrane dynamic model and simple source distribution method is developed. Two different numerical methods, the iteration and whole matrix methods, are developed and both agree well with analytic solutions. Using those computer programs, the performance of a flexible-membrane wave barrier with varying initial tension, length, and mass density is investigated. It is found that almost complete reflection of incident wav...

Flexible-membrane wave barrier. I: Analytic and numerical solutions

A filter device for trapping particulates for diesel engine exhaust gases including an electrical heating element for regenerating the primary monolithic ceramic filter and a porous cermaic disc pre-filter between the heating element and the primary filter to provide a practical secondary source of heat when particulates on it combust during regeneration.

Ceramic foam prefilter for diesel exhaust filter system

The interaction of water waves with a tensioned, inextensible, vertical flexible membrane hinged at the sea floor and attached to a solid cylindrical buoy at its top, was investigated in the context of two-dimensional linear wave-body interaction theory. Both submerged and surface-piercing buoy/membrane wave barriers were considered. A two-domain boundary element program was developed based on a discrete-membrane dynamic model and simple-source distribution over the entire fluid boundaries. Since the boundary condition on the membrane is not known in advance, the membrane motion and velocity potentials were solved simultaneously. The accuracy and convergence of the developed program were checked using the energy-conservation formula. The numerical results were further verified by checking several limiting cases and through comparison with the experiments conducted in a 2D wave tank. Using the developed computer program, the performance of surface-piercing or submerged buoy/membrane wave barriers was tested with varying buoy radius and draft, water depth, membrane length, and mooring-line stiffness. The performance of the three different mooring types was also investigated. From our numerical examples, it can be concluded that the buoy/membrane wave barrier can function as a very effective breakwater if it is properly designed.

Flexible Membrane Wave Barrier. II: Floating/Submerged Buoy-Membrane System

An inflatable dike formed from sections includes an upper and lower partition The lower partition includes a water inlet and is water-fillable via the water inlet to add weight to the dike The upper partition attaches to partially surround to the lower partition The upper partition includes an air inlet for inflating the upper partition with air The upper partition inflates to add rigidity, and to laterally support the lower partition

Portable dike having air inflatable reinforcement

Bragg scattering of waves propagating over a series of poro-elastic submerged breakwaters

A new type of submeged structure called “Flexible Mound” is proposed, which consists of a thin flexible membrane filled with water. A numerical analysis based on the linear potential theory is carr...

Transmission and Reflection Characteristics of Waves Over a Submerged Flexible Mound

A resilient wave reducing structure which reduces waves propagating on liquid surface from propagating over the reducing structure and a method of constructing the wave reducing structure. The wave reducing structure of the present invention may be used to form a calm water surface region for harbors, for areas where construction work is being done or for areas where marine sports are to be performed etc. The resilient wave reducing structure includes at least one energy absorbing device having a resilient body constructed on a bottom of the liquid bounding the region where waves have to be reduced and filled with surrounding ambient liquid. This reduces the amplitude of waves passing over it by consuming the wave energy while it deforms according to the pressure distribution change caused by the waves and by radiating its kinetic energy into the liquid and the ground surrounding it. Because the wave reducing structure is resilient and deeply submerged under water, it does not hinder ships from passing over it. Therefore, it becomes possible to create a calm region on a liquid surface without hindering a navigation of ships and without creating a danger of wrecking the ships.

Submerged flexible wave restraining structure and a method of constructing it

PURPOSE: To prevent the liquefaction of sandy ground at earthquack by providing a drainage consisting of a porous member and granular articles in the sandy ground and thereby controlling the rise of an excessive neutral stress therein. CONSTITUTION: Based on an excessive neutral stress to take place in the ground 1 found in accordance with the magnitude (the size of shearing stress) of an earthquake estimated for the sandy ground 1 and in consideration of the size, importance etc. of a structure, the interval of the following drainage 2 to be laid is selected. The drainage 2 is constructed by filling the ground 1 with a member 3 of spongy or multifiber structure. In addition, a porous pipe body 4 with a bottom is also buried in the ground 1 and filled with large gravels 5 at need, thus the drainage 2 is formed. COPYRIGHT: (C)1980,JPO&Japio

Liquefaction preventing method for sandy ground

PROBLEM TO BE SOLVED: To stably hold a structure constructed on a floating body by discharging water from a water storage pit to bottom the floating body on a bottom of the water storage tank in the case of rainstorm, while keeping the advantages as a floating type base isoration structure usually SOLUTION: A water storage facility 5 is communicated with a water storage pit 1 through a communicating passage 6, and a pump 7 for feeding and discharging water is arranged in the communicating passage 6 Usually, a structure 4 floats in the water storage pit 1 through a floating body 3 so that floating body type base isolating action is obtained for the oscillation caused by an earthquake and the oscillation of the ground 2 due to the earthquake is hardly transmitted to the structure When a storm due to a typhoon comes, the pump 7 is operated to move substantially total amount of water W in the water storage tank 1 into the water storage facilities 5 in order to discharge the water W so that the floating body 3 is bottomed on a bottom part of the water storage tank 1 Consequently, the oscillation is completely prevented, even if a strong wind force F is applied to the structure 4 After the storm is over, the pump 7 is operated to return a predetermined amount of water into the water storage pit 1 from the water storage facilities 5, float the floating body 3 again, and return to the floating body type base isolation structure

Floating type base isolation structure

A new wave-generation system, composed of a source and an absorber, is proposed to realize a non-reflective wave field in a laboratory basin as an advanced alternative to conventional methods. Theoretical studies based on the linear potential theory were carried out to investigate the characteristics of wave fields generated by the proposed method. Performance of the new system was compared to that of conventional serpent-type wave-makers. The proposed system was founded to provide a significantly larger effective area for multi-directional waves than does the serpent-type wave makers. Experimental studies using a two-dimensional wave tank were also conducted to verify the performance and practicality of the new system. The results showed that the new devised equipment can produce a nearly non-reflective wave field and can generate waves efficiently even in deep water.

Tetsushi Kiyokawa

Papers

Transmission and Reflection Characteristics of Waves Over a Submerged Flexible Mound

Submerged flexible wave restraining structure and a method of constructing it

Liquefaction preventing method for sandy ground

Floating type base isolation structure

Non-reflective multi-directional wave generation by source method