The local shear stress and flow structures on symmytical ripples due to oscillatory flow

• Main Authors: Kuo, Li Ani, 郭禮安
• Other Authors: Kuo Ching-Ton
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/33857606712455758691

碩士 === 國立成功大學 === 水利及海洋工程學系 === 84 === In this paper we use the strain gages at the "crest", "lee side" and "trough" in the ripple model . So as to measuring shear stress in oscillatory water tunnel. In addition we employ the "LDV" system to measure the velocity field near the ripple. 1.For measuring shear stress: Indicating that the shear stress at "crest" is larger than at "lee side" . And the one at "lee side" are larger than at "trohgh". We find the flow in this study was rough turbulent flow by using Vongvisessomjai's regime function. And we using Jonsson's definition of friction factor "fw", and the form roughness "Ks" can be calculated from Swart's formula. Finally we using "fw" and "Ks" to do dimensional analysis and gain fitting curve for each other. 2.For measuring velocity: We using the "LDV" system to measure velocity field. We find the condition-"over shooting" at crest. At lee side the flow is confusion, then the velocity profile nonsmoothly. And the velocity profile at the trough is smooth. Finally we get the eddy viscosity "ε" by calculating with measuring shear stress and velocity field profile. In our experiment condition, the eddy viscosity "ε" value approximately ranges from 0.0000392 to 0.000422.