Study of Stay Vanes Vortex-Induced Vibrations with different Trailing-Edge Profiles Using CFD

Abstract

The 2D flow around 13 similar stay-vane profiles with different trailing edge geometries is investigated to determinate the main characteristics of the excitation forces for each one of them and their respective dynamic behaviors when modeled as a free-oscillating system. The main goal is avoid problems with cracks of hydraulic turbines components. A stay vane profile with a history of cracks was selected as the basis for this work. The commercial finite-volume code FLUENT® was employed in the simulations of the stationary profiles and, then, modified to take into account the transversal motion of elastically mounted profiles with equivalent structural stiffness and damping. The k-ω SST turbulence model is employed in all simulations and a deforming mesh technique used for models with profile motion.

The static-model simulations were carried out for each one of the 13 geometries using a constant far field flow velocity value in order to determine the lift force oscillating frequency and amplitude as a function of the geometry. The free-oscillating stay-vane simulations were run with a low mass-damping parameter (m*ζ=0.0072) and a single mean flow velocity value (5m/s). The structural bending stiffness of the stay-vane is defined by the Reduced Velocity parameter (Vr).

The dynamic analyses were divided into two sets. The first set of simulations was carried out only for one profile with 2≤Vr≤12. The second set of simulations focused on determining the behavior of each one of the 13 profiles in resonance.