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The influence of fluid–structure interaction on cloud cavitation about a flexible hydrofoil. Part 2

Smith, SM, Venning, JA ORCID: 0000-0002-4097-2168, Pearce, BW ORCID: 0000-0003-2189-5598, Young, YL and Brandner, PA ORCID: 0000-0002-6721-878X 2020 , 'The influence of fluid–structure interaction on cloud cavitation about a flexible hydrofoil. Part 2' , Journal of Fluid Mechanics, vol. 897 , A28-1-A28-39 , doi: 10.1017/jfm.2020.323.

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The influence of fluid–structure interaction on cloud cavitation about a hydrofoilis investigated by comparing results from a relatively stiff reference hydrofoil,presented in Part 1, with those obtained on a geometrically identical flexible hydrofoil.Measurements were conducted with a chord-based Reynolds number Re = 0.8 × 106for cavitation numbers, σ, ranging from 0.2 to 1.2 while the hydrofoil was mounted atan incidence, α, of 6◦to the oncoming flow. Tip deformations and cavitation behaviourwere recorded with synchronised force measurements utilising two high-speed cameras.The flexible composite hydrofoil was manufactured as a carbon/glass-epoxy hybridstructure with a lay-up sequence selected principally to consider spanwise bendingdeformations with no material-induced bend–twist coupling. Hydrodynamic bend–twistcoupling is seen to result in nose-up twist deformations causing frequency modulationfrom the increase in cavity length. The lock-in phenomenon driven by re-entrant jetshedding observed on the stiff hydrofoil is also evident on the flexible hydrofoilat 0.70 ≤σ ≤ 0.75, but occurs between different modes. Flexibility is observed toaccelerate cavitation regime transition with reducing σ. This is seen with the rapidgrowth and influence the shockwave instability has on the forces, deflections andcavitation behaviour on the flexible hydrofoil, suggesting structural behaviour plays asignificant role in modifying cavity physics. The reduced stiffness causes secondarylock-in of the flexible hydrofoil’s one-quarter sub-harmonic, fn/4, at σ = 0.4. Thisleads to the most severe deflections observed in the conditions tested along with ashift in phase between normal force and tip deflection.

Item Type: Article
Authors/Creators:Smith, SM and Venning, JA and Pearce, BW and Young, YL and Brandner, PA
Keywords: cavitation, fluid-structure interactions, hydrodynamics, multiphase flow
Journal or Publication Title: Journal of Fluid Mechanics
Publisher: Cambridge Univ Press
ISSN: 0022-1120
DOI / ID Number: 10.1017/jfm.2020.323
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Copyright 2020 The Author(s)

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