Investigation of flow upstream of hydropower intakes

Abstract

This thesis is primarily focused on flow-field upstream of hydropower intakes, with emphasis on the use of temperature control curtains and predicting the flow acceleration zone. By reviewing the available literature, it is concluded that the flow-field upstream of hydropower intake systems can be modeled by potential flow theory. The understanding of near intake flow-field can be useful in fish entrainment studies and in designing fish repulsion systems. To control downstream river temperatures, a flexible curtain was installed upstream of several dams in California. Flow downstream of the curtain was analyzed using a Computational Fluid Dynamic (CFD) solver with rigorous validation by experimental data. The experiment was conducted with a 4 beam Acoustic Doppler Velocimeter (ADV) probe. The study shows that wall jet properties downstream of the curtain are affected by the water depth and the inlet Reynolds number. Empirical expressions were developed to predict jet properties and the wall shear stress. Flow upstream of the curtain was analyzed using potential flow theories with validation by the CFD solver. In this part, a theory based on Schwarz-Christoffel transformation was developed to predict the flow-field upstream of the curtain without accounting for any density stratification in the water body. It is observed that the acceleration zone upstream of the curtain can be affected by sink opening size, its location and water depth. The effect of boundaries on flow upstream of a line sink and the interaction of multiple sinks were analyzed. The effect of stratification on a line sink is also analyzed. A theory is developed to predict the incipient withdrawal condition when a sink is located on the horizontal bottom. The theory is also extended to a tilted bottom. The effect of boundaries on the incipient withdrawal condition is analyzed. When only one layer is being withdrawn, it is shown that a homogenous equation can be applied to a stratified condition by assuming an upper layer boundary at the interface. In addition to these works, a despike algorithm for ADV data is developed, and a numerical analysis on central difference scheme is presented.