Hydrodynamic Damping of a Fluttering Hydrofoil in High-speed Flows

Abstract

A hydrofoil resembling a high head Francis runner blade was submerged in a rectangular channel and attached to the walls in a fixed-beam configuration. The hydrofoil was excited by piezoelectric Macrofiber composite actuators (MFCs), and the vibration was measured at the trailing edge with Laser Doppler Vibrometry (LDV) and semiconductor strain gauges. The hydrofoil was exposed to water velocities ranging from 0 to 25 m/s. Lock-in occurred at approx. 11 m/s. The damping increased linearly with the water velocity, with a slope of 0.02 %/(m/s) below lock-in, and 0.13 %/(m/s) above lock-in. The natural frequency of the foil increased slightly with increasing water velocity below lock-in, due to the added stiffness of the passing water. Additionally, the natural frequency increased significantly when passing through lock-in, due to the vortex shedding phase shift.

Model Order Reduction Technique Applied on Harmonic Analysis of a Submerged Vibrating Blade

“…The goal of these experiments is to study the damping characteristics of the fluid-structure system, and importantly, the relationship between the flow velocity and the damping. The experimental setup and results from the unsymmetrical hydrofoil can be found in [25], as well as on the Francis99 project homepage [10]. The same setup is used for the symmetric hydrofoil which will be studied here.…”

Experimental Study of a Low‐Specific Speed Francis Model Runner during Resonance

“…Here Φ j is the acoustic mode with a value for each sensor, j. Based on the measurements by Bergan et al [25] the damping is assumed to be proportional to the water velocity going through the runner.…”

Experimental investigation on the effect off near walls on the eigen frequency of a low specific speed francis runner

“…and 5.4mm towards the upper and lower cover, as shown in Figure 2b. to the setup used by other authors investigating added mass and damping of submerged structures [17,24,2].…”