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A technique for visualising global frequency modes and phasing information is presented using fast Fourier transforms applied to individual pixel intensities of high-speed photography image frames. A singular value decomposition is applied to the resulting complex data set to allow the application of windowing to the transforms. A high-speed image set of cloud cavitation about a sphere is used to demonstrate the technique and identify the dominant cavitation shedding modes. Three frequencies were found and the modal analysis show these to correspond to large-scale near symmetric shedding, intermediate-scale oblique shedding, and smallscale near symmetric shedding, respectively. Results obtained by the presented image analysis technique show close agreement to shedding frequencies obtained from pressure data.

Item Type:	Refereed Conference Paper
Keywords:	cloud cavitation, frequency analysis, modal decomposition
Research Division:	Engineering
Research Group:	Maritime Engineering
Research Field:	Ship and Platform Hydrodynamics
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in Engineering
UTAS Author:	Venning, JA (Dr James Venning)
UTAS Author:	Giosio, DR (Dr Dean Giosio)
UTAS Author:	Pearce, BW (Dr Bryce Pearce)
UTAS Author:	Brandner, PA (Professor Paul Brandner)
ID Code:	131934
Year Published:	2018
Deposited By:	NC Maritime Engineering and Hydrodynamics
Deposited On:	2019-04-12
Last Modified:	2019-06-19
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