Author(s): P. T. K. Ostby; S. Knutsen; J. T. Billdal

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Keywords: No Keywords

Abstract: Methods used to calculate the eigenmodes and eigenfrequencies of a Francis runner with the added mass from water are well established and have been verified by several experiments. The common explanation of the water's role is the added mass it brings to the runners structural eigenmodes and thereby reducing the eigenfrequencies. In this paper we calculate the first eigenfrequency of the runner from the acoustic properties of the runner channel and compare the result with full FEA calculations. Using this method we show that the local speed of sound for the water in the channel can be as low as 200m/s and that the density of the runner is not necessarily an important parameter for the first eigenfrequency with some Nodal Diameters of High Head Runners.

DOI: https://doi.org/10.1088/1755-1315/1079/1/012095

Year: 2022