Richard K. Fisher

Overload Surge Investigation Using CFD Data

Pressure oscillations triggered by the unstable interaction of dynamic flow features of the hydraulic turbine with the hydraulic plant system - including the electrical design - can at times reach significant levels and could lead to damage of plant components or could reduce component lifetime significantly. Such a problem can arise for overload as well as for part load operation of the turbine. This paper discusses an approach to analyze the overload high pressure oscillation problem using computational fluid dynamic (CFD) modeling of the hydraulic machine combined with a network modeling technique of the hydraulic system. The key factor in this analysis is the determination of the overload vortex rope volume occurring within the turbine under the runner which is acting as an active element in the system. Two different modeling techniques to compute the flow field downstream of the runner will be presented in this paper. As a first approach, single phase flow simulations are used to evaluate the vortex rope volume before moving to more sophisticated modeling which incorporates two phase flow calculations employing cavitation modeling. The influence of these different modeling strategies on the simulated plant behavior will be discussed.

Advances in Turbine Development for Fish Survival

Development of a hydraulic turbine that is environmentally safe for fish passage continues to be an evolutionary process. The rate of increase of knowledge of mechanisms causing fish injury and mortality has gained momentum in recent years. Recent endangered fish listings on various stretches of major rivers have placed a priority on continuing this effort. Major research is underway by turbine designers, biologists and plant operators in an effort to understand the mechanisms for fish injury in hydraulic turbines and associated water passage structures. Funding by the Federal Government and certain industrial partners is now being provided to stimulate research on mortality mechanisms and to develop advanced hydro turbines designed to address improved survival.

A CFD Framework for Environmentally-Friendly Hydroturbines

The hydropower industry is faced today with a number of challenging problems arising from regulations that emphasize environmental objectives in the operation of its facilities. In spite of using a renewable, non-polluting source of energy, inconsiderate development can adversely impact the aquatic habitat either by inducing fish mortality or by deteriorating the quality of the tailrace water. This paper summarizes recent results from our ongoing research efforts aimed at developing advanced Computational Fluid Dynamics methods that are capable of assessing and improving the environmental comparability of hydropower installations.