Page - 540 - in Book of Full Papers - Symposium Hydro Engineering

Fig 6. Average Annual Amount of Sediments(in Mt) Second, an assessment of the trapping efficiency was presented. MP must meet the velocity standard, 0.2m/s, to function as a sand trap. So a 2D numerical analysis (using TELEMAC) was conducted at a rate of 153 ㎥/s, the design discharge, and 200㎥/s, the bypass tunnel open condition. The results show that for discharge of 153㎥/s, the flow velocities in the MP do not exceed this limit except locally at the intake. For the discharge of 200㎥/s, there are some areas with velocities greater than 0.2m/s. In most of the MP, however, velocity is still below 0.2m/s. Therefore, the MP can act as a natural sand trap. 3.4. PHYSICAL MODEL INVESTIGATION 3.4.1. Introduction and Basic data Physical model investigation was conducted to verify the performance of sediment management using the OHDS technique. It is conducted by the Laboratory of Hydraulics, Hydrology and Glaciology(VAW) of the Swiss Federal Institute of Technology Zurich(ETH Zurich). The experiments were separated into hydraulic tests with a fixed bed and sedimentological tests with a movable bed and sediment supply. The inflow water flow discharge and suspended sediment data collected from 1960 to 2012 were used. The sediment rating curve described in the Feasibility Study was used to define the amount of suspended material. As well, the bed load was assumed to be 15% of the suspended load based on a conservative review. 3.4.2. Physical model construction In order to choose an appropriate model scale, Froude similarity was applied. This was because for free surface flow, scaling with the Froude law is the most commonly used model that represents the best the general hydraulic phenomena. Table 5 540