Study On 3D Hydraulic Behavior Of Lateral Intake Flow And Its Sediment Control

The thesis serves as a partial fulfillment of the requirement of Doctor Degree. It could also be regarded as the final report of a subproject of the "Study on Sediment, Debris and Pollutant Control of Water Intake of Thermal Nuclear Power Plants " sponsored by the Ministry of Power Industry. It was aimed at the hydraulic-sediment problems arising from 90 lateral open channel water intaking. The main object of this study was to get a better understanding of the flow and the bed-load transport behavior of such lateral flow diversion and the measures for its improvement. Both experimental investigation and mathematical simulating were conducted. 3D flow structures of the related water region were carefully observed and analyzed.The main aspects of the work proceeded and the results obtained were summarized as follows:1. Systematic experiments were carried out in a 14 m X 5m glass flume with a 90 lateral 3m X 0.8m diversion flume. The main parameters were taken (1)the aspect ratio of the intake section and (2)the velocity ratio which was defined as the ratio of the average velocity at the intake section to the approaching velocity of the main channel. Detailed velocity fields of 6 depth layers under different hydraulic conditions were measured by 3D Acoustic Doppler Velocimeter. It has been demonstrated: The remarkable non-uniformity of the velocity distribution at the intake entrance and its high dependence on . The lateral velocity near the bottom is somewhat larger than that of the upper layer. The largest kinetic energy k and shear stress of turbulence of the lateral flow occurred near the bottom and downstream side of the intake section.2. The 3D velocity, Reynolds stress and turbulent kinetic energy distributions of the lateral intake flow were also analyzed by solving the Reynolds-averaged Navier-Stokes equations closed with the anisotropic Reynolds Stress Model. Thorough comparisons of the calculated results and measured values were performed. The good agreement indicated theadoptability and credibility of the numerical approach used. Parametric studies were thus extended and more hydraulic behaviors of the flow revealed.3. In comply with the flow characteristics at the intake water region, two simple but effective measures for sediment control have been suggested: using sloped or staggered bottom sill with higher elevation downstream side at the entrance section, adding bottom guide plate just upstream of the entrance section.4. Detailed patterns of helical flow induced by a guide plate were obtained and analyzed. The optimum arrangement of the guide plate and the relevant "protected length P" could be predicted under some given condition. A semi-empirical formula for assessing the helical velocity distribution in lateral diversion flow is presented.