| Project/Area Number |
11450188
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
水工水理学
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| Research Institution | Nagoya University |
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Principal Investigator |
IWATA Koichiro Grad.School of Eng., Nagoya Univ., Professor, 大学院・工学研究科, 教授 (10029150)
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| Co-Investigator(Kenkyū-buntansha) |
TAKEHARA Kohsei School of Science and Eng., Kinki Univ., Associate Professor, 理工学部, 助教授 (50216933)
NOCHINO Masao School of Eng., Osaka Inst.of Eng., Professor, 工学部, 教授 (10116080)
ETOH Takeharu School of Science and Eng., Kinki Univ., Professor, 理工学部, 教授 (20088412)
SUMI Hirokazu School of Eng., Kanazawa Inst.of Eng., Associate Professor, 工学部, 講師 (10314048)
KAWASAKI Koji School of Eng., Osaka Univ., Research Associate, 大学院・工学研究科, 助手 (20304024)
IWATA Koichiro Grad.School of Eng., Nagoya Univ., Professor (10029150)
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| Project Period (FY) |
1999 – 2002
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| Keywords | Wave breaking limit / Air-water interface / Triple-type wave breaking / PTV / Air bubble generation mechanism / Wave pressure change / Wave sound / Ultra-sonic videocamera |
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| Research Abstract |
This research aims to develop a new ultra-high speed video-camera to measure the wave breaking inception and formation and collapsing of air bubbles at the air-water interface as accurately as possible and to investigate the breaking wave-caused turbulence by means of laboratory experiments and numerical calculation.
Main results obtained are as follows :
(1) An In-situ Storage Image Sensor (ISIS) of 1,000,000 fps with linear Charge Coupled Device (CCD) has been newly developed and an ultra-high speed video-camera of 1,000,000 fps with high sensitivity has been successfully manufactured for the fist time in the world.
(2) Kalman filtering and Chi-square Method (KC Method) has been much improved to trace the water particle motion after wave breaking. Using the new ultra-high speed video-camera (l,000,000 fps) and the improved KC Method, air bubble formation and collapsing process are filmed with very high accuracy for the first time in the world. The effect of viscosity and surface tension to the air bubble formation and collapsing are investigated.
(3) Surface tension waves are formed on the front surface of wave and are grown up. The front water surface is broken by the air-wrapping effect of the grown critical surface tension wave and air bubbles are introduced in the water body.
(4) FFT method and discrete wavelet analyses have revealed that high frequency components of water pressure rapidly increase after formation of air bubbles and that the sound wave is generated by the motion of air bubbles in water.
(5) The sound wave pressure decays inverse proportional to the distance from air bubble formation point and its magnitude is well estimated theoretically with the theory of spherical wave propagation.
(6) 3-dimensional numerical computation method DOLFIN has been newly developed, by extending CIP and SMAC methods, to evaluate the solid-water-air combined flow.
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