越流型水制の周りにおける流速分布 : 現地観測と数値シミュレーション
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Velocity distribution around submerged spur dikes : field observation and numerical simulation
primary and intermittent vortex
two-dimensional flow model
finite element method
At meander concave bank, Spur dike is appropriate for protecting bank from erosion and control bed topography. But the flow around spur dike are occur transverse component of spiral current. The meander zone is expanded to overcome the frictional resistance of the channel boundary in case during floods. So, without designing spur dike by more carefully using detail survey, numerical simulation and laboratory experimentation test, the scour and deposition of sediment occur a undefined and unexpected place by the stream flow variations caused by flood. Numerical simulation a two-layer model was developed as the extension of the two-dimensional flow model could get good result, comparing with field measurement distributions of velocity around spur dikes in Ushizu River, Saga Prefecture Kyushu region. The field observation continued from 1994 to 1996 covering the pre-and past-construction periods of the spur dikes. The characteristics of physical current at low and high water have been studied through field measurement and numerical simulation using two dimensional flow models. At result of spiral current, primary and intermittent vortex deflected current could define by numerical simulation. This basic equations are constructed by the finite element method to be appropriate for complicated topography like around spur dikes.