Spillway plunging jets and aeration: State-of-the-art assessment

Plunging jets are created by a wide variety of natural and man-made structures, each application usually having significantly different flow conditions. Numerous studies have been, performed to gain a better understanding of plunging jets. These studies have included basic experimental tests, physical models, prototype field investigations, and computational models. However, because of the complex two-phase flow conditions associated with plunging jets, adequate evaluation methods are still not available to accurately predict specific conditions in a stilling basin. The purposes of the research presented in this thesis are to determine the current state-of-the-art and identify potential improvements for evaluating spillway plunging jets with specific emphasis towards impacts on fish survival.; A comprehensive review of existing literature concerning plunging jets is presented. The emphasis of this review is on information to assist directly with the evaluation and design of alternatives to improve fish passage and survival. The review documents the current understanding of theories governing plunging jets and methods used for evaluation of design alternatives. Case studies for Rock Island Dam and Wanapum Dam are presented to explore the application of the state-of-the-art. These case studies illustrate how hydraulic model studies can be used to evaluate plunging jet impact pressures that can potentially injure fish and deflector alternatives to reduce total dissolved gas (TDG). Hydraulic model limitations are also presented.; Because of hydraulic model limitations in evaluating plunging jets, improved computational models are needed to better evaluate plunging jets and fish passage alternatives. The use of computational models has been limited because of inadequate information about velocity patterns, turbulence, and air bubble distribution in stilling basins. Improved non-intrusive measurement methods are needed to obtain this required information. This thesis presents an evaluation of Acoustic Doppler Velocimetry (ADV) and Particle Image Velocimetry (PIV) as non-intrusive measurement methods to obtain measurements in plunging jets. The capability and limits of ADV and PIV for measuring velocity and air concentration in complex stilling basin flows are presented. It is concluded that improvements in measuring stilling basin flow parameters can be achieved with ADV and PIV.