Structure-structure coupling by liquids: Vibration measurements on a rotating disk with self-tracking LDV

Weder, Mario; Horisberger, Beat; Monette, Christine; Dual, Jürg

doi:10.1063/1.4952685

Cited by 1 publication

(1 citation statement)

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“…Numerical Fluid-Structure Interactions (FSI) models using Finite Element Analysis (FEA) are powerful tools for the structural design analysis of these machines (Dompierre & Sabourin, 2010;Hübner et al, 2016). This method is applicable to natural frequency prediction of standing circular plates (Hengstler, 2013), disk-fluid-disk systems, rotor-stator systems (Specker, 2016;Weder et al, 2016Weder et al, , 2019, and rotating disks in fluid (Weber & Seidel, 2015). This shows that the application range of numerical FSI is extremely broad, and widely used to deal with disk frequency prediction.…”

Section: Introductionmentioning

confidence: 99%

Modal analysis of a spinning disk in a dense fluid as a model for high head hydraulic turbines

Louyot

Nennemann

Monette

et al. 2020

Journal of Fluids and Structures

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In high head Francis turbines and pump-turbines in particular, Rotor Stator Interaction (RSI) is an unavoidable source of excitation that needs to be predicted accurately. Precise knowledge of turbine dynamic characteristics, notably the variation of the rotor natural frequencies with rotation speed and added mass of the surrounding water, is essential to assess potential resonance and resulting amplification of vibrations. In these machines, the disk-like structures of the runner crown and band as well as the head cover and bottom ring give rise to the emergence of diametrical modes and a mode split phenomenon for which no efficient prediction method exists to date. Fully coupled Fluid-Structure Interaction (FSI) methods are too computationally expensive; hence, we seek a simplified modelling tool for the design and the expected-life prediction of these turbines.We present the development of both an analytical modal analysis based on the assumed mode approach and potential flow theory, and a modal force Computational Fluid Dynamics (CFD) approach for rotating disks in dense fluid. Both methods accurately predict the natural frequency split as well as the natural frequency drift within 7.9% of the values measured experimentally. The analytical model explains how mode split and drift are respectively caused by linear and quadratic dependence of the added mass with relative circumferential velocity between flexural waves and fluid rotation.

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