查詢結果分析
來源資料
頁籤選單縮合
| 題 名 | 泥砂顆粒帶起機率之研究=An Investigation on Pickup Probability for Sediment Entrainment |
|---|---|
| 作 者 | 吳富春; 林曜成; | 書刊名 | 農業工程學報 |
| 卷 期 | 47:1 2001.03[民90.03] |
| 頁 次 | 頁87-93 |
| 分類號 | 443 |
| 關鍵詞 | 帶起機率; 泥砂揚起; 機率分佈; 無因次剪應力; 上升力; Pickup probability; Sediment entrainment; Probability distribution; Dimensionless shear stress; Lift force; |
| 語 文 | 中文(Chinese) |
| 中文摘要 | 渠道中水流之輸砂能力與泥砂顆粒帶起機率關係密切,本研究以理論方式探討泥砂顆粒被水流帶起之機率,並與文獻資料進行比較。渠道中泥砂顆粒所承受之上升力大於其有效重量時,泥砂顆粒即被帶起而產生移動,上升力之大小與近床水流速度有密切關聯。過去之相關研究初步假設近床速度之機率分佈為常態分佈,並利用實驗資料推估亂流流況時近床水流速度之平均值及標準偏差與剪力速度之關係,進而推求泥砂顆粒在不同剪應力下之帶起機率。然而根據理論值與實驗值之比較顯示近床速度假設為常態分佈導致顯著之誤差,因此本研究乃以較合於物理現象之對數常態分佈探討泥砂顆粒之帶起機率,以增進計算精度。研究結果顯示近床水流速度假設為對數常態分佈計算所得帶起機率與實驗數據更為吻合,可降低50%以上之誤差。在相同的流況及上升力係數條件下,對數常態分佈有較高的帶起機率,約為常態分佈所得帶起機率之4~6倍。 |
| 英文摘要 | The transport of sediment in open-channel flows is closely related to its pickup probability. This study theoretically investigates the pickup probability for sediment entrainment and compares the results with the published data. When the flow-induced lift force for a particle is greater than its submerged weight, the movement of sediment particle will occur. The lift force is a function of the near-bed velocity approaching to the particle. The previous study has assumed that the probability density of the near-bed velocity is normally distributed and used the experimental mean value and standard deviation to formulate a theoretical relationship between the pickup probability and the dimensionless shear stress. However, the previous result reveals a significant error as compared to the experimental data. This study aims to improve the accuracy by using the log-normal distribution to characterize the near-bed velocity because it is more physically reasonable for open-channel flows. The results indicate that the pickup probability derived from the log-normal distribution is in better agreement with the experimental data. The improvement of the accuracy exceeds 50%. Under the identical flow condition and the lift coefficient, the pickup probability derived from the log-normal distribution is approximately 4-6 times of that from the normal distribution. |
本系統中英文摘要資訊取自各篇刊載內容。