Simulation of reservoir density current and muddy lake during storm

• Main Authors: Chun-Wei Wang, 王竣葦
• Other Authors: Kwan Tun Lee
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/39543140288405339821

碩士 === 國立臺灣海洋大學 === 河海工程學系 === 101 === Hillslopes in Taiwan are usually steep with rapid flow. Severe erosion and even large scale landslide usually occur in concentrated rainstorms, which result in a large amount of sediment flowing through overland areas to channel network and then to downstream reservoir to reduce the useful life of reservoir. Since the density of the sediment laden flow is different from reservoir ambient water, the turbidity flow plunges into the reservoir bottom as a density current. The behavior of the turbidity current in the reservoir was simulated by using a density current model to imitate the turbidity plunging into the reservoir bottom and move to the dam site. A second-order MacCormack scheme was adopted to simulate the one-dimensional unsteady density current. A simplified muddy-lake model based on mass conservation and empirical equations was also developed for reservoir operation to estimate the reservoir outflow concentration. Three major parameters, the water entrainment coefficient (Ew), the total drag coefficient (Cd), and the settling velocity (vs) were calibrated using the data from series saline-density-current flume tests. Sensitivity analysis was conducted to realize the influences of the coefficients on the thickness, velocity, and concentration of the density current. Good agreement can be found between the simulated and the recorded data using the calibrated Ew, Cd, and vs. Moreover, hydrological records from severe typhoons in the Tseng-wen reservoir of Taiwan were collected to demonstrate the capability of the proposed model for density current simulation. The developed model is promising to provide valuable information to authorities for reservoir operating to reduce reservoir sedimentation.