複断面開水路に生じる大規模組織渦と浮遊砂輸送 [in Japanese] ORGANIZED HORIZONTAL VORTICES AND LATERAL SEDIMENT TRANSPORT IN COMPOUND OPEN CHANNEL FLOWS [in Japanese]
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複断面開水路では低水路と高水敷の境界部に大規模な組織渦が生じ, それが横断方向の運動量・物質輸送に大きな影響を与えることが知られている. 本研究ではSDS-2DHモデルを実験室スケールの複断面流れ場に適用し, 同モデルが時間平均流速, Reynolds 応力, 卓越波長をほぼ説明できることを示した. あわせてその流れ場のもとで浮遊砂の移流拡散を計算した結果, 浮遊砂濃度が組織渦による特徴的な分布パターンを示し, 横断方向への浮遊砂の輸送過程を再現できた.
It has been known that the shear instability generates large horizontal vortices at the junctions of main channel and flood plains for two-stage channels. The present laboratory tests show that the horizontal vortices appear for flow with small relative depth. For channels with bank vegetation, horizontal periodic vortices also appear for small relative depth, and it was seen that the vortices in the main channel is predominant.<br>Numerical computations were performed by employing SDS-2DH turbulence model, and the results obtained agree reasonably well with the experiments. The model can predict the wavelength of horizontal vortices, the lateral distributions of the Reynolds stress, temporally-averaged longitudinal flow velocity, etc. The numerical simulation, which was performed for lateral transport of suspended sediment, has revealed that the transport is closely correlated with the large scale horizontal vortices.
- Proceedings of the Japan Society of Civil Engineers
Proceedings of the Japan Society of Civil Engineers 656, 135-144, 2000-08-21
Japan Society of Civil Engineers