ORCID Profile
0000-0001-5320-7222
Current Organisation
Australian Maritime College
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Publisher: AIP Publishing
Date: 2023
DOI: 10.1063/5.0132054
Abstract: The influence of nucleation on cavitation inception in a high Reynolds number shear layer in the wake of a backward-facing step was experimentally investigated in a water tunnel. The flow was investigated for two nuclei populations: the one naturally occurring in the water and for the water artificially seeded with monodisperse nuclei. Incipient events were observed to form in stretched quasi-streamwise vortices. The collapse of an incipient cavity resulted in a microbubble cloud dispersed into the shear layer and the step re-circulation zone. These microbubbles, generally larger than those naturally occurring in the water, act as preferential sites for re-nucleation, triggering the formation of developed cavitation. This phenomenon rendered statistical characterization of cavitation inception impractical for the natural nuclei population. The re-nucleation issue was addressed by seeding the flow with a population of large monodisperse nuclei, with a critical pressure higher than that of cavitation products. Spatial distribution of the nuclei within the seeded plume was characterized using a volumetric measurement based on Mie-scattering imaging. The ability to discern in idual incipient events enabled examination of the effect of cavitation number and the nuclei injection rate on the inception event rate. The event rate was found to follow a power law with cavitation number and vary linearly with the injection rate. Mapping of spatial distribution of cavitation susceptibility was obtained by combining the spatial distributions of incipient events and nuclei concentration. The current work provides a valuable dataset for the development of computational tools for modeling of cavitation inception in nucleated flows.
Publisher: AIP Publishing
Date: 2023
DOI: 10.1063/5.0132034
Abstract: Cavitation in a tip leakage flow is experimentally investigated in a cavitation tunnel using a stationary hydrofoil analogy. The experiments were performed for different tip clearances (τ=gap height/maximum profile thickness) and hydrofoil incidences (α). The chord-based Reynolds number remained fixed at Re=3×106. The influence of nucleation on both inception and developed cavitation is evaluated by performing tests with two populations of freestream nuclei: a low concentration with strong critical tensions for activation and a high concentration with weak critical tensions. These populations represent the extremes that would be expected in practical tip leakage flows. Cavitation was characterized using high-speed imaging and acoustic measurements. Following a survey of developed cavitation topology for a range τ and α values, α=6° was selected for further investigation of cavitation inception as it demonstrated a rich variety of physical processes. From the acoustic measurements, the worst performance in terms of cavitation inception was observed at an intermediate gap height of around τ=0.6–0.8 for the “strong water” case. Broadly, cavitation and inception is intermittent when nuclei are sparse, becoming continuous as additional nuclei are introduced. While a continuous cavity in the seeded flow resulted in a higher baseline acoustic signature, sparse populations allow the leakage vortex to sustain tension, which can result in extremely loud incipient events. Optimization of gap height will, therefore, depend on the expected nuclei population during operation.
Publisher: Springer Science and Business Media LLC
Date: 22-02-2020
Publisher: ASME Press
Date: 2018
Publisher: Springer Science and Business Media LLC
Date: 20-01-2017
No related grants have been discovered for Patrick Russell.