吳富春2006-07-252018-06-292006-07-252018-06-2920032003-07-31http://ntur.lib.ntu.edu.tw//handle/246246/10737泥砂顆粒之啟動機率為序率輸砂模式中不可或缺之要素，其精確與否影響輸砂率推估 之準確性，進而影響河川整治之成效。過去之研究並未有系統地探討泥砂顆粒啟動之機 制，亦未明確界定泥砂顆粒滾動與抬起之門檻條件，甚或採用不一致之啟動機率推導輸砂 模式，致使預測結果與實測資料差距甚大。本研究之目的即有系統地探討泥砂顆粒滾動與 抬起之門檻條件，並推估在不同流況下泥砂顆粒之啟動機率，進而將其應用於序率輸砂模 式推估礫砂河床之分區輸砂率。This study addresses the rolling and lifting probabilities for sediment entrainment by incorporating the probabilistic features of the turbulent fluctuation and bed grain geometry. The two threshold conditions identified herein enable us to precisely define the probabilities of entrainment in the rolling and lifting modes. The lifting probability increases monotonously with the dimensionless shear stress θ, consistent with the earlier results yet displaying improved agreement with the experimental data. The maximum value of rolling probability, with a magnitude of 0.25, occurs at 15 . 0 ≈ θ . For 05 . 0 < θ (or 6 . 0 > θ ), the rolling (or lifting) probability makes up more than 90% of the total entrainment probability and thus can be used as an approximation to the total entrainment probability. The rolling and lifting probabilities are further linked to two separate criteria for incipient motion. The results reveal that a consistent probability corresponding to the critical state of sediment entrainment cannot be found.application/pdf64455 bytesapplication/pdfzh-TW國立臺灣大學生物環境系統工程學系暨研究所滾動與抬起機率泥砂啟動亂流跳動河床幾何Rolling and lifting probabilitiessediment entrainmentturbulent fluctuationbed geometryreporthttp://ntur.lib.ntu.edu.tw/bitstream/246246/10737/1/912211E002037.pdf