Experimental investigation on the influence of gap vortex streets on fluid-structure interactions in hexagonal bundle geometries

Experimental investigation on the influence of gap vortex streets on fluid-structure interactions in hexagonal bundle geometries

Bertocchi, F. (TU Delft RST/Reactor Physics and Nuclear Materials)
Rohde, M. (TU Delft RST/Reactor Physics and Nuclear Materials)
Kloosterman, J.L. (TU Delft RST/Radiation, Science and Technology)

RST/Radiation, Science and Technology

2019

Gap vortex streets characterise many industrial applications involving rod bundle flows, such as heat exchangers and nuclear reactors. These structures, known as gap vortex streets, may excite the structural components of the bundle to resonance, leading to fretting and fatigue. This work aims to measure these coherent structures and the resulting displacement and oscillation frequency of the neighbouring rod, to provide unique data for fluid-structure interaction studies and to develop a general correlation for estimating the coherent structure's wavelength. A water loop was built to host a hexagonal rod bundle. Fluorinated Ethylene Prophylene (FEP), a refractive index matching (RIM) material, was used to have undisturbed optical access in the area around the central rod. The flow was measured with Laser Doppler Anemometry (LDA) to detect coherent structures, while the vibrations were measured with a high speed camera. A new correlation for estimating the wavelength of the coherent structures is derived with dimensional analysis based on experimental evidence. The correlation is tested on different geometries: rectangular channels with single or half-rods, and two rod bundles, within the pitch-to-diameter ratio (P/D) range 1.02–1.2. Moreover fluctuations in the flow, given by the detected coherent structures, govern the structural response of the rod. The rod is excited to resonance if these fluctuations match twice the natural frequency of the rod.

Coherent structures
Fluid-structure interactions
Laser Doppler Anemometry
Rod bundle

http://resolver.tudelft.nl/uuid:cfc0e61e-d384-4a78-a431-c24c1096c73f

https://doi.org/10.1016/j.ijheatfluidflow.2019.108443

2020-04-23

0142-727X

International Journal of Heat and Fluid Flow, 79

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2019 F. Bertocchi, M. Rohde, J.L. Kloosterman