- 作者: 李鴻源; 許盈松
- 作者服務機構: 國立臺灣大學土木工程學系; 國立臺灣大學水工試驗所
- 中文摘要: 水流中近床區域泥砂顆粒躍移機制的研究對於推移載運動理論的發展具有重要的意義。本研究運用「即時一流場顯影技術」與「高速攝影技術」,能在不影響流況的情況下,同時量測許多傳統方法所無法測得之數據,包括泥砂運動軌跡、運動速度及旋轉速度。試驗過程中採用不同顆粒條件和不同水流強度的組合,系統地量測了底床附近顆粒的躍移過程,得出在不同水流強度下躍移顆粒之最大躍高、最大躍長、縱向躍移平均速度及躍移旋轉速度。 本文同時提出顆粒單步躍移歷程之物理模式,在已知水流及顆粒條件下,本模式可模擬顆粒躍移軌跡與躍移過程中之速度、加速度及各作用力之沿程變化特性。與試驗結果相驗證,發現本文所建立的物理模式對近床區域泥砂顆粒躍移特性之模擬相當準確,同時發現躍移過程中的馬格納斯效應為一不可忽略的因素,應該加以考慮。經由本文之研究,可以清楚瞭解躍移顆粒之運動特性,對往後進一步深入探討底床質輸砂量推估之理論研究,有極大的助益。
- 英文摘要: A real-time flow visualization technique and a high-speed photographic technique were developedin this study to measure particle trajectories, velocities, and spinning rates.Different combinations ofwater depths, channel slopes, particle sizes, particle shapes, and particle densities were tested. Regressionequations for the dimensionless average saltation length, height, and velocity, lift-off spinning rates andlongitudinal variations of the spinning rates were obtained. A mathematical model which is able to simulateparticle single-step saltation behaviors is developed herein.This model is able to calculate the particletrajectories and the longitudinal variations of the velocities, accelerations, and corresponding forces actingupon the particle. The simulated saltation trajectories agree well with the experimental data. It is alsofound that the Saffman force and Magnus force play a very important role in the saltation process and,hence, cannot be neglected.
- 中文關鍵字: sediment transport; bed load transport; saltation; real-time flow visualization technique; highspeed photographic technique
- 英文關鍵字: --