圖書典藏及影音數位平台

石岡壩自921地震後下游河床因下切嚴重，而發生河床面之向源侵蝕現象，對石岡壩的結構安全造成嚴重的威脅。 雖然石岡壩之土木設施有定期之檢查與維護，但對於可能發生的原因，並沒有進一步的力學分析與計算。因此，本計畫將對於壩體、靜水池及下游河道進行三維數值模擬分析，希望進一步了解水工結構物之複雜流場及作用力，有助於後續改善工程之規劃與設計。

This project aims to develop a 3D numerical computation model in order to carry out the simulation of the fluid filed near Shingang dam located in Daja River. This 3D numerical computation model is established by means the ANSYS computation fluid mechanics software based on the exact digital-elevation map within and the hydraulic structures of the Shihgang dam, including the dam body, the associated gates, the energy-dissipation pool, the protection dike, the side dam, and the downstream river channel. It can be also known that aforementioned digital data should be investigated and corrected based on the latest design planning report. In addition, under the consideration of the scale effect of the hydraulic structure, two types of computation grids are adopted in the proposed 3D numerical simulation model: (1) the low resolution, in which the length of the gird is about 0.2 cm - 2m, used in the hydraulic structure; and (2) the other is high resolution (1 m – 2m) applied the river channel. In addition to the numerical simulation, this project intends to measure the speed profile of the surface flow at the Befong Bridge located at downstream of Shihgang dam using the radar RiverSurveyor_M9 produced by SonTek company. Specifically, the maximum speed which can be recorded by RiverSurveyor_M9 approximates 20 m/s within a possible range of water depth about 0.2 m to 80 m. Before simulating the entire fluid filed in the Shihgang dam watershed, the proposed 3D numerical model should be demonstrated in the cases of discharges from numerous gates, i.e. 48.6 cms, 71.5 cms and 63.7 cms, respectively. The verification results present that the average speed estimated by the 3D numerical model ranges from 0 m/s to 2 m/s and it is similar to the observation (about 0.5 m/s – 2 m/s). This reveals that the proposed 3D numerical model for the Shihgane dam can 國家高速網路與計算中心 摘要 National Center for High-Performance Computing VII reasonably simulate the temporal variation of the fluid filed and flow characteristics in the downstream area of the dam under the various conditions of outflow.