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The dynamics of cloud cavitation about a three-dimensional hydrofoil are investigated experimentally in a cavitation tunnel with depleted, sparse and abundant free-stream nuclei populations. A rectangular planform, NACA 0015 hydrofoil was tested at a Reynolds number of 1.4 × 10⁶, an incidence of 6◦ and a range of cavitation numbers from single-phase flow to supercavitation. High-speed photographs of cavitation shedding phenomena were acquired simultaneously with unsteady force measurement to enable identification of cavity shedding modes corresponding to force spectral peaks. The shedding modes were analysed through spectral decomposition of the high-speed movies, revealing different shedding instabilities according to the nuclei content. With no active nuclei, the fundamental shedding mode occurs at a Strouhal number of 0.28 and is defined by large-scale re-entrant jet formation during the growth phase, but shockwave propagation for the collapse phase of the cycle. Harmonic and subharmonic modes also occur due to local tip shedding. For the abundant case, the fundamental shedding is again large-scale but with a much slower growth phase resulting in a frequency of St = 0.15. A harmonic mode forms in this case due to the propagation of two shockwaves; an initial slow propagating wave followed by a second faster wave. The passage of the first wave causes partial condensation leading to lower void fraction and consequent increase in the speed of the second wave along with larger-scale condensation. For a sparsely seeded flow, coherent fluctuations are reduced due to intermittent, disperse nuclei activation and cavity breakup resulting in an optimal condition with maximum reduction in unsteady lift.

Item Type:	Refereed Article
Keywords:	cavitation inception, nuclei, nucleation, hydrofoil
Research Division:	Engineering
Research Group:	Maritime engineering
Research Field:	Ship and platform structures (incl. maritime hydrodynamics)
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in engineering
UTAS Author:	Venning, JA (Dr James Venning)
UTAS Author:	Pearce, BW (Dr Bryce Pearce)
UTAS Author:	Brandner, PA (Professor Paul Brandner)
ID Code:	154797
Year Published:	2022
Deposited By:	NC Maritime Engineering and Hydrodynamics
Deposited On:	2023-01-09
Last Modified:	2023-02-09
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