本研究利用沙漣底床所造成之剪力摩擦而導致波浪能量的減衰，以能量耗損率的觀點，藉由實驗波高的紀錄，進而推估動床實驗下不同沙漣規模所相對應之摩擦係數f/sub w/，並以沙漣幾何形狀與流況得到動床經驗式為f/sub w/ =1.5468(η/sub m//sup 2//λ/sub m/a)/sup 0.64/；結果發現其f/sub w/值均較前人利用定床沙漣模型測其剪力所得到的結果為小。顯示底床沙漣的非對稱性，變動性與具遷移性，對於流體運動作用於底床之作用力大小有顯著的影響。利用Swart(1976)之半經驗公式，求得沙漣形狀粗糙度K/sub s/，發現 K/sub s/=0.9-2.7η/sub m/；且其相對形狀粗糙度K/sub s//η/sub m/與 Shields參數Ψ存在一指數關係式：K/sub s//η/sub m/=7.8Ψ/sup 0. 837/。 In this study, the effects due to the existence of the ripples on the changes of wave heights are studied in order to estimate the related friction factor f/sub w/. In which functional relationships between the ripple geometry and hydraulic parameters were derived as f/sub w/=1.5468(.eta./sub m//sup 2//.lambda./sub m/a)/sup 0.64/. The results of moving bed experiments are smaller than the former results of fixed artificial rippled shear plate. The form roughness K/sub s/ can be calculated from Swart's formula (1976), and K/sub s/ is about 0.9-2.7.eta./sub m/. The experimental results reveal that the relation between the equivalent form roughness K/sub s//.eta./sub m/ and Shields parameter .PSI. is K/sub s//.eta./sub m/=7.8.PSI./sup 0.837/.
Relation:
第二十屆海洋工程研討會論文集=Proceedings of the 20th Ocean Engineering Conference in Taiwan, R.O.C.，頁500-506
