Throughout the design and planning period for future hydroelectric generating stations, hydraulic engineers are increasingly integrating computational fluid dynamics (CFD) into the process. As a re...

Assessment of spillway modeling using computational fluid dynamics

In the present work, a numerical study was performed to analyze the flow behavior in a reservoir in the presence of strong vortices. A challenging subject in this study was the flow field in the reservoir and the mechanism of vortex formation. The numerical model was verified with the available theories and experimental data. Experiments were conducted in a reservoir in which strong vortices were formed over an intake. Measurements of the flow field were carried out with an Acoustic Doppler Velocimeter (ADV) for a constant intake submerged depth and two different intake Froude numbers. The agreement between numerical and experimental results for 3D velocity field was good. Finally, using the validated numerical results, the flow behavior in the reservoir was analyzed. A funnel shape flow pattern was recognized in the reservoir toward the intake and its boundaries were identified. Another flow pattern observed was a spiral vortex motion from the water surface towards the intake. The present paper i...

Numerical Simulation and Analysis of Flow In A Reservoir In The Presence of Vortex

In recent years, the design flood estimates of a number of dams in Australia have been revised, requiring their spillways to be upgraded to cope with increased flood discharges. Traditionally, reduced scale physical models were used in hydraulic laboratories to study spillway hydraulic performance. However, these are prone to problems associated with scaling effects, and cannot readily capture behaviours such as cavitation and air-entrainment effects, which can occur in reality. Nowadays, with the advancement in computing technology, the hydraulic performance of spillways can be investigated numerically. Since 2001, a number of spillway upgrade projects in Australia have been performed using computational fluid dynamics. This paper provides an overview of how this technology was applied to these projects. The validation process to ensure the numerical model is reliable, and various analysis capabilities allowing better understanding of the flow behaviour will be described. Current limitations are also highlighted in order that future research and development can resolve them, thus making this numerical modelling technique more robust for flow simulation of not just spillways, but also other hydraulic structures in the future.

Application of computational fluid dynamics to evaluate hydraulic performance of spillways in australia

Orifice spillways are in vogue for the dams in the hilly regions where the spillway has to serve the dual function of flood disposal and flushing of sediment through the reservoir. Deep-seated orifice spillways are subjected to cavitation damage as the cavitation index drops below the critical cavitation index of 0.2 because of negative pressures on the profile and high flow velocities. Aerators are provided for mitigating cavitation damage. Design guidelines for aerator of orifice spillways are scanty and not reported much in the literature so far; thus, there still remains gray area in the field of spillway aerator design. The present study investigates the performance of an offset aerator with and without a ramp for deep-seated orifice spillway on a physical and numerical model. Performance of the aerator for varying discharges, heads, and gate openings is studied for varying cavity subpressures. Results with respect to jet length, cavity subpressure and air entrainment coefficients are present...

Orifice Spillway Aerator: Hydraulic Design

Computational Fluid Dynamics (CFD) is used extensively by engineers to model and analyse complex issues related hydraulic design, planning studies for future generating stations, civil maintenance, supply efficiency, and dam safety. The integrity of computed values from CFD models is of considerable economic importance in the design, upgrading and maintenance of hydroelectric generating stations. CFD models have the ability to predict many characteristics flow over a spillway and Manitoba Hydro has had good agreement with physical model results in the past. However, date there has not been a review that brings all the available information together for a comprehensive assessment. The objective of this research is to build upon previous investigations on the use of CFD modelling, by focusing specifically on the ability to accurately model spillways using CFD. This paper discusses three-dimensional numerical modelling of several different spillway configurations using the CFD software Flow-3D and compares the predicted rating curves, pressures, and water surface elevations to corresponding physical model experimental values. The numerical model results were generally in agreement with physical model data, however, the relative differences in discharges were found to have a P/Hd dependency. The accuracy for a given model resolution and associated computational time required was also considered.

https://espace.library.uq.edu.au/view/UQ:120908/Chanel_afmc_16_07.pdf

An evaluation of computational fluid dynamics for spillway modeling

Hydropower Dam designers and developers are discovering the capabilities of computational fluid dynamics for a range of applications, from hydraulic design to the analysis of dam break flooding. The design and engineering assessment of hydroelectric facilities involves developing an understanding of the very complex behaviour of moving water. To accomplish this, the engineer must develop a thorough understanding of the complexities of fluid flow phenomena - complexities that are often highly two and three dimensional in nature. In early years, physical model studies would have been the only practical medium available to gain insight into the threedimensional and time-dependent nature of fluid flow. However, physical modelling is typically only undertaken during the final stages of design, and can be costly to execute. With the advancements in computing power made since the 1980's, CFD analysis has emerged as a powerful alternative design tool, and can be used to provide insight into hydraulic design at all levels of study. Manitoba Hydro and Acres International Ltd., both of Winnipeg, Manitoba, Canada, have undertaken an extensive 3-dimensional modelling program as a part of pre-commitment level studies for three proposed hydropower projects in Northern Manitoba. These three projects are the Gull Generating Station (680 MW) on the Nelson River, near Gillam, Manitoba, and the Notigi (100 MW) and Wuskwatim (200 MW) Generating Stations, both on the Burntwood River, near

David M. Fuchs

Papers

COMPUTATIONAL FLUID DYNAMICS: DIVERSE APPLICATIONS IN HYDROPOWER PROJECT's DESIGN AND ANALYSIS