投潭水作用下局部沖刷之沖刷率研究

Study on the Scour Rate Below Weirs by Free Overfall Flows

陳正炎(Jen-Yan Chen) ； 彭思顯(Shih-Hsien Peng) ； 鐘文傳(Wen-Chwan Jong)

《中華水土保持學報》 25卷3期 (1994/09) Pp. 135-141

https://doi.org/10.29417/JCSWC.199409_25(3).0002

摘要

本文旨在利用一系列不同堰高H_d，單寬流量q所組成之各種投潭水流作用於均匀粒徑渠床，配合渠床縱向流速場之檢測，以探討堰壩下游局部沖刷之淘刷行爲。經由理論分析之推導與觀測數據之驗證得知，投潭水所造成之瞬時局部沖刷剖面可用最大刷深h_(st)予以無因次化，且得無因次之最大刷深處水平距L_(st)/h_(st)≒0.88，最大坑長L(it)/h(st)≒3.05、剖面面積因子A_s，平均值約爲1.72，以及單寬沖刷率係隨時間增加而成冪次方遞減之定量、定性關係。

關鍵字

投潭水 ； 沖刷剖面 ； 面積因子 ； 沖刷率

並列摘要

The scouring phenomenon of free overfalls, constructed by a series of different weir heights H_d and unit width discharges q, acting on uniform graded-channel bottoms were studied. An electronmagnetic current meter was used to measure the velocity of the downstream flow of the weirs to explore the velocity field. Meanwhile, a theoretical formula was derived for analytical purpose. Results from experiments and analytical solutions were compared to study the scour rate. Based on the analysis of the observed data, several conclusions can be draw. The area factor of scour profile A_s equaled to 1.72; the dimensionless horizontal location of the maximum scour depth L_(st)/h_(st) and the dimensionless maximum scour length L_(it)/h_(st) approached to 0.88 and 3.05 respectively. Besides, the scour rate per unit width decreased with time in an exponential rate.

並列關鍵字

Free Overfall Flow ； Scour Profiles ； Area Factor ； Scour Rate