水庫壩體坡度影響異重流運移之試驗研究
Other Title
Research of Density Current Movement by Variant Slopes of the Dam
Journal
台灣水利
Journal Volume
58
Journal Issue
2
Start Page
11
End Page
21
ISSN
0492-1550
Date Issued
2010-06
Author(s)
Abstract
當水庫集水區水流進入水庫後，因流速減緩使得輸砂能力降低，其挾帶入庫的泥砂可能沉降庫底或形成水庫異重流，若入庫的泥砂在水庫形成異重流且運移至壩體時，其運動行為將受到下游壩體形狀之影響。本研究進行水槽試驗，用以探討壩體附近無排砂操作情況下，水庫異重流運移至壩前，受阻於不同水庫壩體坡度後產生的現象及行為。由試驗結果可知，在相同單寬入流量及濃度下，異重流在壩體斜坡之爬升速度以及最大爬升高度與壩體坡度成正比關係；但在相同壩體坡度與單寬入流流量下，異重流最大爬升高度與異重流壅高高度反比於入流濃度；此外，試驗結果分析得知，異重流正湧波之波速主要受理查遜數（Richardson number）、異重流正湧波所行之相對距離及壩體坡度之影響。本研究異重流正湧波波速之經驗式，可供不同壩體坡度的水庫概算出異重流正湧波回溯上游之距離及速度，有助於估算形成渾水水庫所需的時間。
When turbidity current flows into a reservoir, the main cause of sedimentation problem is the sediment transport ability. The sediment transport ability decays by means of velocity when turbidity current flows into a reservoir. After that, the inflow sediment may deposit on the bottom of the reservoir or develops to the density current. When density current develops and moves to the downstream, its flow mechanism is affected by dam. Therefore, this study focus on the behavior and character of density current during density current is affected by different dam slopes. The experimental results present the density current climbing velocity and the maximum climbing height are directly proportional to the dam slopes. But, the maximum density current climbing height and its thickness are inverse proportional to the inflow concentration. On the other hand, the positive surge is mainly affected by Richardson number, the relative distance traveled by positive surge and dam slopes. Based on this research, the experimental formulas can utilize to compute positive surge velocity under variant slopes of the dam. It can be helpfully to estimate the timing of reservoir turning into turbidity.
Subjects
異重流
理查遜數
壩體坡度
正湧波
Density current
Richardson number
Dam slopes
Positive surge
Type
journal article