Author(s): C Ibanez; R Gustavsson

Linked Author(s):

Keywords: CFD; Added mass; Added damping; Kaplan turbine; Rotor dynamics

Abstract: This paper evaluates the use of CFD to compute added mass, added moment of inertia and added damping on a model scale Kaplan turbine surrounded by still water for different types of oscillatory motions and runner blade angles. The motions investigated are radial and axial translation, as well as radial and axial rotation. Different oscillatory frequencies (or maximum accelerations) are considered. The added mass and moments of inertia obtained are compared against structural acoustic simulation (SAS) results for the same geometry. Both CFD and SAS calculations show good agreement and similar trend for varied runner blade opening angles in both open water and with waterways configuration. The added mass (or moment of inertia) and added damping parameters from CFD are included in a rotor dynamic analysis. A comparison is made between including and excluding the extra added damping alongside the extra added mass (or moment of inertia). It is shown that the addition of added damping does not influence the extent of natural frequencies, but gives more stability to the system. Given that SAS is computationally faster and cheaper than CFD and since added damping has little effect on varying eigenfrequencies, the SAS method can therefore be considered a more precise alternative than traditional methods when it comes to design purposes and the calculation of added mass and added moment of inertia.

DOI: https://doi.org/10.1088/1755-1315/1483/1/012031

Year: 2023