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On the unsteady behaviour of cavity flow over a two-dimensional wall-mounted fence

Citation

Barbaca, L and Pearce, BW and Ganesh, H and Ceccio, SL and Brandner, PA, On the unsteady behaviour of cavity flow over a two-dimensional wall-mounted fence, Journal of Fluid Mechanics, 874 pp. 483-525. ISSN 0022-1120 (2019) [Refereed Article]

Copyright Statement

Copyright 2019 Cambridge University Press

DOI: doi:10.1017/jfm.2019.455

Abstract

The topology and unsteady behaviour of ventilated and natural cavity flows over a two-dimensional (2-D) wall-mounted fence are investigated for fixed length cavities with varying free-stream velocity using high-speed and still imaging, X-ray densitometry and dynamic surface pressure measurement in two experimental facilities. Cavities in both ventilated and natural flows were found to have a re-entrant jet closure, but not to exhibit large-scale oscillations, yet the irregular small-scale shedding at the cavity closure. Small-scale cavity break-up was associated with a high-frequency broadband peak in the wall pressure spectra, found to be governed by the overlying turbulent boundary layer characteristics, similar to observations from single-phase flow over a forward-facing step. A low-frequency peak reflecting the oscillations in size of the re-entrant jet region, analogous to ‘flapping’ motion in single-phase flow, was found to be modulated by gravity effects (i.e. a Froude number dependence). Likewise, a significant change in cavity behaviour was observed as the flow underwent transition analogous to the transition from sub- to super-critical regime in open-channel flow. Differences in wake topology were examined using shadowgraphy and proper orthogonal decomposition, from which it was found that the size and number of shed structures increased with an increase in free-stream velocity for the ventilated case, while remaining nominally constant in naturally cavitating flow due to condensation of vaporous structures.

Item Details

Item Type:Refereed Article
Keywords:cavitation, multi-phase flows
Research Division:Engineering
Research Group:Maritime Engineering
Research Field:Ship and Platform Hydrodynamics
Objective Division:Manufacturing
Objective Group:Transport Equipment
Objective Field:Nautical Equipment (excl. Yachts)
UTAS Author:Barbaca, L (Dr Luka Barbaca)
UTAS Author:Pearce, BW (Dr Bryce Pearce)
UTAS Author:Brandner, PA (Professor Paul Brandner)
ID Code:134280
Year Published:2019
Deposited By:NC Maritime Engineering and Hydrodynamics
Deposited On:2019-08-06
Last Modified:2019-09-16
Downloads:0

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