scholarly journals NUMERICAL SIMULATION FOR TSUNAMI-HEIGHT REDUCTION USING A VERY LARGE FLOATING STRUCTURE

2017 ◽  
pp. 24
Author(s):  
Taro Kakinuma ◽  
Tatsuya Nakahira ◽  
Takatsugu Kamba ◽  
Takahiro Murakami ◽  
Keisuke Nakayama
Keyword(s):  
Water Waves ◽  
Flexural Rigidity ◽  
Reduction Rate ◽  
Two Dimensional ◽  
Floating Structure ◽  
Tsunami Height ◽  
Tsunami Propagation ◽  
Height Reduction ◽  
Very Large Floating Structure ◽  
Crest Line

The tsunami-height reduction using a very large floating structure, i.e., VLFS, is discussed, with the water waves, interacting with a floating thin-plate, simulated numerically. The final tsunami-height reduction rate increases, as VLFS length, VLFS flexural rigidity, or the wave height of an incident tsunami, is increased. If two VLFSs are utilized, the final tsunami-height reduction rate, also depends on the distance between the VLFSs. In two-dimensional tsunami propagation, another wave propagates to the outside, along the crest line of the main wave, leading to an additional tsunami-height reduction.

scholarly journals A NUMERICAL SIMULATION OF TSUNAMI-HEIGHT REDUCTION USING A VERY LARGE FLOATING STRUCTURE

2015 ◽  
Vol 71 (2) ◽  
pp. I_1033-I_1038
Author(s):  
Tatsuya NAKAHIRA ◽  
Taro KAKINUMA ◽  
Takatsugu KAMBA ◽  
Takahiro MURAKAMI ◽  
Keisuke NAKAYAMA ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Floating Structure ◽  
Tsunami Height ◽  
Height Reduction ◽  
Very Large Floating Structure

scholarly journals Surface and Internal Waves due to a Moving Load on a Very Large Floating Structure

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Taro Kakinuma ◽  
Kei Yamashita ◽  
Keisuke Nakayama
Keyword(s):  
Thin Plate ◽  
Internal Waves ◽  
Water Waves ◽  
Moving Load ◽  
Fluid Motion ◽  
Point Load ◽  
Internal Mode ◽  
Floating Platform ◽  
Floating Structure ◽  
Very Large Floating Structure

Interaction of surface/internal water waves with a floating platform is discussed with nonlinearity of fluid motion and flexibility of oscillating structure. The set of governing equations based on a variational principle is applied to a one- or two-layer fluid interacting with a horizontally very large and elastic thin plate floating on the water surface. Calculation results of surface displacements are compared with the existing experimental data, where a tsunami, in terms of a solitary wave, propagates across one-layer water with a floating thin plate. We also simulate surface and internal waves due to a point load, such as an airplane, moving on a very large floating structure in shallow water. The wave height of the surface or internal mode is amplified when the velocity of moving point load is equal to the surface- or internal-mode celerity, respectively.

Effects of Aircushion Division to Hydroelastic Responses of an Aircushion Type Very Large Floating Structure

2003 ◽  
Author(s):  
Tomoki Ikoma ◽  
Koichi Masuda ◽  
Hisaaki Maeda ◽  
Chang-Kyu Rheem
Keyword(s):  
Water Waves ◽  
Final Section ◽  
Three Dimensional ◽  
Offshore Structure ◽  
Floating Structure ◽  
Distribution Method ◽  
Steady Wave ◽  
Elastic Deflection ◽  
Momentum Theory ◽  
Very Large Floating Structure

A target offshore structure in this study is an aircushion supported very large floating structure. The aircushion type VLFSs behave elastically in water waves. Corresponding aircushions are very large or relatively small size. The VLFSs considered in this study are supported by a large aircushion, two aircushions, or several module aircushions. The zero-draft theory is applied to the prediction of the hydrodynamic forces. The zero-draft theory is based on the pressure distribution method. The elastic deflection predicted by the zero-draft method is compared with that by another three-dimensional method in order to confirm the validity of it. In addition, the steady wave drifting forces on VLFSs with the aircushion are shown and their characteristics are examined. Then, the momentum theory is applied to the prediction. In the final section, effects of aircushion division to the elastic deflection and the wave drifting force are investigated. From the results, it is confirmed that the elastic deflection is can be reduced in the specification relation between the wavelength and the length of a module aircushion. In addition, it is possible to ajust the aircushion setting in order to simultaneously reduce the elastic deflection and the steady wave drifting force of the aircushion type VLFS on the case.

A Prediction Method of Hydroelastic Motion of Aircushion Type Floating Structures Considering With Draft Effect Into Hydrodynamic Forces

2008 ◽  
Author(s):  
Tomoki Ikoma ◽  
Masato Kobayashi ◽  
Koichi Masuda ◽  
Chang-Kyu Rheem ◽  
Hisaaki Maeda
Keyword(s):  
Potential Theory ◽  
Water Waves ◽  
Large Scale ◽  
Prediction Method ◽  
Linear Potential ◽  
Wave Loads ◽  
Floating Structure ◽  
Model Experiments ◽  
Very Large Floating Structure ◽  
Linear Potential Theory

An aircushion type floating structure can prevent to enlarge the wave drifting force restraining the hydroelastic response of it in water waves. The floating structure should be large scale to incident waves in order to make the best use of such advantages, i.e. it is a very large floating structure. The linear potential theory is useful to easily handle the wave force etc. on the aircushion type floating structure theoretically because it is predicted that its theory can give good results of behaviors of water elevation within aircushions and pressure and of wave loads on the structure qualitatively. The authors have confirmed from our past model experiments that non-linear effect does not always increase but for some exceptions. A prediction method of hydroelastic responses for the aircushion type very large floating structure by using the three-dimensional linear potential theory is shown in this paper. The validity of the method is proven and the application of the method is investigated by comparing the theoretical results with the results of the past model experiments.

scholarly journals New exact relations for steady irrotational two-dimensional gravity and capillary surface waves

2017 ◽  
Vol 376 (2111) ◽  
pp. 20170220 ◽  
Author(s):  
Didier Clamond
Keyword(s):  
Free Surface ◽  
Gravity Waves ◽  
Water Waves ◽  
Two Dimensional ◽  
Physical Plane ◽  
Theme Issue ◽  
Nonlinear Water Waves ◽  
Dimensional Gravity ◽  
Irrotational Motion ◽  
Exact Relations

Steady two-dimensional surface capillary–gravity waves in irrotational motion are considered on constant depth. By exploiting the holomorphic properties in the physical plane and introducing some transformations of the boundary conditions at the free surface, new exact relations and equations for the free surface only are derived. In particular, a physical plane counterpart of the Babenko equation is obtained. This article is part of the theme issue ‘Nonlinear water waves’.

FABRICATION OF TWO-DIMENSIONAL PHOTONIC CRYSTALS WITH GE2SB2TE5 NANOHOLE ARRAYS BY NANOSPHERE LITHOGRAPHY

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1300-1305
Author(s):  
KI-HO SONG ◽  
HYUN-YONG LEE ◽  
HOE-YOUNG YANG ◽  
SUNG-WON KIM ◽  
JAE-HEE SEO ◽  
...  
Keyword(s):  
Photonic Crystals ◽  
Plasma Treatment ◽  
Treatment Time ◽  
Reduction Rate ◽  
Nanosphere Lithography ◽  
Two Dimensional ◽  
Photonic Bandgaps ◽  
Nanohole Arrays ◽  
Plasma Treatment Time ◽  
Lift Off

Two-dimensional photonic crystals (2D-PCs) with Ge 2 Sb 2 Te 5 ( GST ) nanohole arrays were prepared by the nanosphere lithography (NSL) process. A primary factor of PCs is that the refractive index (n) and the n-modulation can be realized by using the GST films, which exhibit a reversible phase transformation between amorphous and crystalline states by laser illumination. The polystyrene (PS) spheres with a diameter of 500 nm were spin-coated on Si substrate and subsequently reduced by O 2-plasma treatment. The reduced spheres were utilized as a lift-off mask of the NSL process and their size and separation could be precisely controlled. Amorphous GST films were thermally evaporated and then the reduced PS spheres were removed. The fabricated GST nanohole arrays were observed by SEM and AFM. The nanohole diameters are nearly linearly reduced with increasing plasma-treatment time (t). The reduction rate (δ) for the conditions of this work was evaluated to be ~ 0.92 nm/s. The period (Λ) and filling factor (η) of PCs are structure parameters that determine their photonic bandgaps (PBGs). η-modulation can be easily achieved via a control of t and the Λ can be also modulated by the use of PS spheres with specific diameter. In addition, the PBGs for the fabricated GST 2 D PC were calculated by considering the amorphous and crystalline states of GST .

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