| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1994: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1993: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
The objectives of this study are to investigate the effects of the sway of flexible standing roughness elements on the profiles of mean velocity, turbulence intensities and Reynolds stress, and to develop a theoretical model which can explain the experimental results.
A relationship between the deflection of reeds and water velocity was investigated in order to understand the physical characteristice of reeds, e.g.flexural rigidity.
The reeds as the roughness elements were used Hydrilla verticillata(L.f).Casp.KUROMO and Potamogeton oxyphyllus Miquel, YANAGIMO.The experiments were conducted in a recirculating open channel 7.0m long, 0.4m wide, and 0.4m deep. The roughness elements were placed in a bed 0.9m long with the same distance in a between in a square lattice. For each roughness, the experiment was divided to three cases.
In this model, the momentum equations are derived for the steady uniform flow and the displacement of roughness elements is analyzed as the static deflection problem of cantilever, in which the hydrodynamic force is converted into the external force acting on the roughness elements. The flow field may be conveniently separated into two region ; (1)the outer region, which corresponds to the region above roughness elements, (2)the inner region, which corresponds to the region within roughness elements.
The analytical velocity profile show that the theory could bu used efficiently to predict the characteristics of flow.
The hydrodynamic force acting on one roughness element is assumed to be proportional to the projected area in the flow-direction and to the square of mean velocity, and the displacement of roughness elements is derived from the bending moment at an arbitrary position.
The calculated deflection of the roughness element agree to all of the experimental profiles with exception of the case of slow velocities.
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