Author(s): Pradeep Narrain; Nigel G. Wright
Linked Author(s):
Keywords: Water engineering; Computational methods; CFD; Low head hydropower
Abstract: Growing energy demand together with increasing environmental concerns has widened the scope of hydropower generation. In addition to conventional hydropower technology, several innovative hydropower machines have been developed in the last decade. Many of these new generation machines that have been constructed for low ratings are still in the developmental stage. As part of an EU project (www. hylow. eu) numerical models were used to understand better the physical processes involving free surfaces in rotating machines using computational fluid dynamics (CFD) simulation software. This includes implementing direct simulations using Volume-of-Fluid (Vo F) methods for free surfaces. This paper will present the approach to the numerical modelling of the machine and the parameters used in the setup of the simulation model. Various parameters such as choice of mesh elements, mesh consistency, choice of boundary conditions and turbulence model are discussed. Further development of the numerical model to improve design and efficiency of the machines will be presented. To ensure that the boundary conditions used are realistic, experimental results performed on a test rig were used to verify the models. With the help of this rig, flow measurements were performed around the machine. These measured quantities provide real boundary conditions for the numerical simulations. On the basis of the experimental data, the simulation results were checked and were used for the further development of the machines. This approach enables a better understanding of flow conditions during operation through the visualisation of flow patterns. The basic model supplies results that are plausible and match those of the experiments enabling modifications of the machine geometry e. g. blade angles to be made on the simulation models. The model can then be so modified and till a maximum efficiency is obtained in the simulations.
Year: 2015