| Project/Area Number |
61302061
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| Research Category |
Grant-in-Aid for Co-operative Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
Hydraulic engineering
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| Research Institution | The University of Tokyo |
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Principal Investigator |
TAMAI Nobuyuki Professor, Dept. of Civil Eng., Univ. of Tokyo, 工学部, 教授 (90010818)
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| Co-Investigator(Kenkyū-buntansha) |
ASAEDA Takashi Assoc. Prof., Dept. of Civil Eng., Univ. of Tokyo, 工学部, 助教授 (40134332)
OHASHI Masakazu Assist. Prof., Dept. of Mathematics, Chuo Univ., 理工学部, 専任講師 (90160598)
OONARI Hirofumi Assoc. Prof., Dept. of Civil and Architecture Eng., Tokuyama Technical College, 土木建築工学科, 助教授 (30045041)
KOMATSU Toshimitsu Assoc. Prof., Dept. of Civil and Water Eng., Kyusyu Univ., 工学部, 助教授 (50091343)
NEZU Iehisa Assoc. Prof. Dept. of Civil Eng., Kyoto Univ., 工学部, 助教授 (30109029)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Turbulence / Coherent Structure / Inner Layer / Outer Layer / Separation Bubble / Boil / Free Shear-Layer / 混合層 / 連行 |
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| Research Abstract |
Coherent sturucture in turbulent flows is a new topic from historical point of view in the research on turbulence. Therefore, the role of coherent structures in hydraulic engineering problems has not been clarified and fully understood yet. A comprehensive study is sought to reach to a unified view and relationships among several problems. The main emphasis is laid on open channel flows and the study consists of two parts. The one is a fundamental part which aims at finding out cherent structures in inner and outer layers in open channel flows. The other is an application part in which the role of coherent vortices in open channel flows and in a shear layer is treated.
With simultaneous application of flow visualization techniques and a laser doppler anemometer, spatial and temporal cherent features of longitudinal vortices in an inner layer of an open channel flow were obtained. One to one correspondence between a time siries of signal of velocity and a transverse pattern of longitudinal vortices was found out. Average duration time in the longitudinal direction was specified. For longitudinal vortices in an outer layer, rotational spectrum was utilized. Near the bottom and the water surface, strong correlation was found in two-point probability density of vertical velocity.
At a downstream facing step, turbulence structures including pressure and the Reynolds stress were measured. Variation of the separation bubble and the merging of separation eddied are two major triggers to produce kolk-boil eddies at the rear of a step. Three-dimensional structure of separation eddies and horse-shoe vortices in fornt of a hemisphere was clarified. Features of a single vortex and its effect on average velocity fild over a favorable slope were clarified.
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