Investigation on the hydrodynamic damping using prescribed blade motion techniques

conference paper

en

Increasing requirements for a high efficiency in a wide operating range of hydraulic turbines lead to turbine designs being more susceptible for periodic and stochastic excitation forces. For periodic excitations like rotor-stator interaction, a large distance to runner natural frequencies is not always possible. And stochastic excitation may cause the runner to respond directly with one of its natural frequencies. Therefore, in both cases, the quantification of damping for runner mode shapes is necessary to predict dynamic stresses and to ensure the required lifetime. The main goal of this paper is to present numerical investigations of the hydrodynamic damping using unsteady CFD analyses with prescribed structural motion. The investigation is carried out on a simple hydrofoil, which is placed in a the cavitation tunnel test section. The natural vibration shape of the hydrofoil is prescribed as a periodic motion with the corresponding frequency. As a prerequisite, natural frequency and mode shape have to include the effects of water environment. Two different approaches (in time and frequency domain) have been applied and compared to 2-way fluid-structure-interaction analysis with respect to accuracy and calculation time. In addition numerical results are validated by compa

Increasing requirements for a high efficiency in a wide operating range of hydraulic turbines lead to turbine designs being more susceptible for periodic and stochastic excitation forces. For periodic excitations like rotor-stator interaction, a large distance to runner natural frequencies is not always possible. And stochastic excitation may cause the runner to respond directly with one of its natural frequencies. Therefore, in both cases, the quantification of damping for runner mode shapes is necessary to predict dynamic stresses and to ensure the required lifetime. The main goal of this paper is to present numerical investigations of the hydrodynamic damping using unsteady CFD analyses with prescribed structural motion. The investigation is carried out on a simple hydrofoil, which is placed in a the cavitation tunnel test section. The natural vibration shape of the hydrofoil is prescribed as a periodic motion with the corresponding frequency. As a prerequisite, natural frequency and mode shape have to include the effects of water environment. Two different approaches (in time and frequency domain) have been applied and compared to 2-way fluid-structure-interaction analysis with respect to accuracy and calculation time. In addition numerical results are validated by compa

hydrodynamic damping, blade, swirling flow, runner, turbine

20.12.2019

1755-1315

IOP Conference Series: Earth and Environmental Science

405

2019

1–6

6