Hostname: page-component-5f745c7db-rgzdr Total loading time: 0 Render date: 2025-01-06T23:41:36.115Z Has data issue: true hasContentIssue false
  • English
  • Français

The flow structure in the near field of jets and its effect on cavitation inception

Published online by Cambridge University Press:  10 November 1999

SHRIDHAR GOPALAN ,
JOSEPH KATZ  and
OMAR KNIO
SHRIDHAR GOPALAN
Affiliation:
Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD 21218, USA
JOSEPH KATZ
Affiliation:
Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD 21218, USA
OMAR KNIO
Affiliation:
Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD 21218, USA
Get access Rights & Permissions [Opens in a new window]

Abstract

Cavitation experiments performed in the near field of a 50 mm diameter (D) jet at ReD = 5 × 105, showed inception in the form of inclined ‘cylindrical’ bubbles at axial distances (x/D) less than 0.55, with indices of 2.5. On tripping the boundary layer, cavitation inception occurred at x/D ≈ 2, as distorted ‘spherical’ bubbles with inception indices of 1.7. To investigate these substantial differences, the near field of the jet was measured using PIV. Data on the primary flow, the strength distribution of the ‘streamwise’ vortices and the velocity profiles within the initial boundary layers were obtained. The untripped case showed a direct transition to three-dimensional flow in the near field (x/D < 0.7) even before rolling up to distinct vortex rings. Strong ‘streamwise’ vortices with strengths up to 25% of the jet velocity times the characteristic wavelength were seen. Cavitation inception occurred in the core of these vortices. In contrast, in the tripped jet the vortex sheet rolled up to the familiar Kelvin–Helmholtz vortex rings with weak secondary vortices. Using the measured nuclei distribution, strengths and straining of the ‘streamwise’ structures, the rates of cavitation events were estimated. The estimated results match very well the measured cavitation rates. Also, the Reynolds stresses in the near field of the jet show similar trends and magnitudes to those of Browand & Latigo (1979) and Bell & Mehta (1990) for a plane shear layer.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 398 , 10 November 1999 , pp. 1 - 43
Copyright
© 1999 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)