Author(s): Oyvind Pedersen; Nils Ruther
Linked Author(s): Nils Rüther
Keywords: No Keywords
Abstract: Hydropower peaking has become extremely popular among the energy suppliers when it comes to production of energy from an electrical hydropower plant. Electricity is produced in times of the day where the demand is high. Since these periods are short and frequently reoccurring, it can happen that the water level in the river is changing heavily during one day. The effects of this frequent changes has been studied recently, however many effects remain yet unknown, e.g. the effects of the frequent flow changes on the river bed. There are several hypotheses on how the river bed is behaving. However, there are few data sets available that describes the total distribution of bed shear stress over time in a river. Therefore does this study attempt to predict bed shear stresses by means of computational fluid dynamics (CFD). One commercial and one in-house CFD program is used to predict the bed shear stress during a hydro power peaking event. Both codes work with a finite volume technique to solve the Reynolds-averaged Navier Stokes equations. The goal of the study was to investigate the capability of the models to simulate hydrodynamic effects from the unsteady flow on the river bed. Measurements of discharge, waterlines and flow velocities were taken at three different flow rates. The results showed that both models are able to calculate the hydrograph given. The flow pattern and the velocity distribution matched well for both calculations.