THE STRUCTURES OF SPACE-TIME CORRELATIONS IN UNSTEADY OPEN-CHANNEL FLOW OVER DUNES

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  • 河床波上非定常開水路流れの時空間相関構造に関する研究
  • カショウハジョウ ヒテイジョウ カイスイロ ナガレ ノ ジクウカン ソウカン

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Abstract

In open-channel flows such as rivers and estuaries, various coherent vortices are often observed and greatly affect sediment transport. These coherent structures often occur especially in flooded fluvial rivers. The hydrodynamic behavior of flood structures is quite different between the rising and falling stages of flood period. In the rising stage, the concentration of suspended sediment increases owing to the kolk-boil vortex because the rising stage corresponds to the growing period of dunes and because separated vortex from the dune collides intermittently at the next dune and washes out bed materials around there. Therefore, it is very important to investigate unsteadiness effects on the coherent structures in unsteady open-channel flows so that the growing process of the dunes and the behavior of the suspended sediment can be explained dynamically. In the present study, the specific behaviors of coherent vortices over dunes were accurately measured by means of simultaneous use of two sets of LDA. The differences of convection properties on coherent vortices between the rising and falling stages were discussed by evaluating the conventional and conditional space-time correlation structures.

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