報告書番号

N08022

タイトル（和文）

河床変動を考慮したダム放流・貯水池内流動の3次元数値解析－ダム改修計画事例への適用－

タイトル（英文）

Three dimensional numerical simulations on dam discharge and flow field in a dam reservoir considering bed deformation

概要 （図表や脚注は「報告書全文」に掲載しております）

ダム形状の影響を考慮してダム貯水池内での流動及び河床変動を解析する手法を提案した．ダム改造計画事例へ本手法を適用することにより，本手法の妥当性を調べた．まず，非静水圧3次元数値モデルRESERV3D version 2007を用いてダム近傍での流動を調べた．次に，この計算から得られた貯水池内水位を下流端境界条件として用いて，ダムから上流100-2300mの領域を対象とした流動と河床変動を静水圧3次元数値モデルC-HYDRO3D reservoirにより計算した．まず，提案した手法の妥当性を確認するために，1/50空間スケールでの河床変動解析を実施し，計算結果を室内実験結果と比較した．そして，侵食領域における侵食量の再現性が優れていることを確認した．次に，実機スケールの計算を実施した．貯水池横断方向に見られるダム形状に起因した水位差は，現状ダムのケースではダム堤体から5m上流まで，改造ダムのケースでは50m上流まで見られることがわかった．改造ダムでの侵食・堆積地点における侵食・堆積量は現状ダムでのそれらより大きいことがわかった．また，流量が増加するにつれて，侵食・堆積箇所における侵食量及び堆積量は大きくなるが，局所的な侵食・堆積位置は流量にほとんど依存しないことがわかった．

概要 （英文）

We propose a method to analyze flow and bed deformation in a dam reservoir, which are effected by its dam form. In our method, first, non-hydrostatic three-dimensional numerical simulations are carried out to investigate flow patterns near the dams, using Reserv3D version 2007. Next, by using the water levels in the reservoirs obtained by the numerical simulations as downstream boundary conditions, hydrostatic three-dimensional numerical simulations are carried out to investigate flow patterns and bed deformations in the region of 100m-2300m upstream of the dams. In order to investigate the validation of the proposed method, we apply this method to reservoirs of both the before-renovated and after-renovated dams. First, bed deformation analyses under a 1/50 scale are carried out and the numerical results are compared with those of laboratory experiment. It is confirmed that erosion volumes at erosion regions obtained by the numerical simulations agree with those obtained by the laboratory experiment. Then, we carry out the numerical simulations under actual scale. The results show that, although water level differences in the transverse direction induced by the dam forms are observed in the region of 5m upstream of the before-renovated dams, they were observed in the region of 50m upstream of the after-renovated dams. The total potential head in the reservoir of after-renovated dam is approximately 4m higher than that of before-renovated dam. The erosion (or deposition) volumes at the erosion (or deposition) regions in the case of after-renovated dam are larger than those in the case of before-renovated dam. On the other hand, the locations, where the erosion and deposition were observed, were independent of the flow volume.

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