The effects of sampling location and turbulence on discharge estimates in short converging turbine intakes

Abstract

Standards provide recommendations for best practice when installing current meters to measure fluid flow in closed conduits. A central guideline requires the velocity distribution to be regular and the flow steady. Because of the nature of the short converging intakes typical of low-head hydroturbines, these assumptions may be invalid if current meters are intended to be used to estimate discharge. Usual concerns are (1) the effects of the number of devices, (2) the sampling location and (3) the high turbulence caused by the presence of fish diversion screens. These three effects were examined in the present study by using 3D simulated flow fields in both steady-state and transient modes. In the process of describing an application at an existing hydroturbine intake at Ice Harbor Dam, the present work outlined the methods involved, which combined computational fluid dynamics, laboratory measurements in physical models of the hydroturbine, and current meter performance evaluations in experimental settings. The main conclusions in this specific application were that a steady-state flow field sufficed to determine the adequate number of meters and their location, and that both the transverse velocity and turbulence intensity had a small impact on estimate errors. However, while it may not be possible to extrapolate these findings to other field conditions and measuring devices, the study laid out a path to conduct similar assessments in other applications. ARTICLE HISTORY

Numerical simulation and analysis of five-stage lifting pump by improved turbulence model and catastrophe theory

“…Many researchers have studied turbulence and discovered the law of turbulence, which is the variation of energy fluctuation with time-scale or wave number (Chen, Chen, Eyink, & Sreenivasan, 2003;Falkovich & Ryzhenkova, 1992;Frisch, 1995;Liang, Wu, & Zhong, 2017;Young & Read, 2017). So, the other two important variables for the turbulent phase transition are the energy spectrum (E k ) and time index factor (g) (Frisch, 1995;Layek & Sunita, 2018;Montoya, Nieto, Alvarez, Hernandez, & Jurado, 2018;Romero-Gomez, Harding, & Richmond, 2017).…”

Fish Response to Turbulence Generated Using Multiple Randomly Actuated Synthetic Jet Arrays

“…The CFD velocities in the upstream model were compared with experimental velocities measured within a reduced-scale model of the turbine geometry. The reduced-scale experimental velocities were measured using laser Doppler velocimetry (LDV) at the location shown in Figure A1a and scaled up using Froude scaling to compare with the full-scale values [20,21,33]. To the best of our knowledge, the aforementioned features have not been simultaneously implemented in the modeling of flow in a complete turbine system.…”

Field validation of an actuated convergent-beam acoustic Doppler profiler for high resolution flow mapping

“…Other scenarios of high spatial variability in a velocity flow field include the short convergent intake structure typical of most low-head Kaplan turbine hydropower plants. The nonhomogeneous flows in both the forebay [14] and the intake structures [15] also represent flow environments which require greater measurement resolution than that offered by a conventional ADCP.…”