Wind induced countercurrent flow in shallow water

This thesis presents a study of wind-generated flow in shallow water, which may occur in lakes, tailings ponds or other closed low-aspect ratio (height/width) water bodies. The main focus was on wind-generated flow motions associated with water covers overlying mine tailings. There are two major parts of the thesis.; In the first part, experimental and numerical studies of the evolution of surface shear-induce countercurrent flow were conducted. A two-dimensional lid-driven cavity apparatus was developed to explore the flow structure in low aspect ratio cavities. A critical aspect ratio for the onset of fully developed countercurrent flow was presented.; In the second part, experimental and theoretical studies were carried out to examine the countercurrent flow motions generated by wind-induced surface shear and waves in a closed shallow water body. A synchronized LDV measurement of velocity, wind waves, and pressures was conducted in a wind-wave tunnel. A triple decomposition method and phase averaging method were used to analyze the velocity data. Under intermediate water wave conditions, it was found that while periodic fluid velocities vary at the frequency of the surface waves, a vortex structure travels downstream in the direction of wind. A mathematical model of the fluid velocity was developed to express the time-averaged distribution and periodic nature of such flow. A periodic varying bed shear stress was also found, which varied at the frequency of the surface wave under intermediate water wave conditions. A model was developed to predict shear stress distribution in such flow, which is also capable of estimating the bed shear stresses.