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Date of Award

6-1994

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Supervisor

P.E. Wood

Abstract

The flow of jets in confining enclosures has significant application in many engineering processes. In particular, two jet flows have been studied; the impingement of axisymmetric jets in a confined space and a turbulent inlet wall jet in a confining enclosure.

The impingement ofaxisynunetric jets in a cavity has been examined using
flow visualization, laser Doppler anemometry, and numerical simulations. When the
flow fIeld was examined under various geometrical and fluid parameters several flow
regions were found, depending on the geometrical and fluid parameters. Initially, a
steady flow field existed for all arrangements for Red < -90 but subsequent increments in the fluid velocity caused an oscillating flow field to emerge. The onset of the
oscillations and the upper limit of fmite oscillations were found to be a function of the
nozzle diameter to chamber dimeasion ratio. Although steady numerical simulations
predicted the steady flow field well. steady simulations of the oscillating flow field
over-predicted the peak axial velocities. The oscillating flow field is considered to be
a class of self-sustaining oscillations where instabilities in the jet shear layer are
amplified because of feed back from pressure disturbances in the impingement region.

The turbulent wall jet in a cavity has been studied using flow visualization,
laser Doppler anemometry (LDA), particle streak velocimetry (PSV) and numerical
simulations. Instantaneous PSV measurements agreed well with time averaged LDA measurements. Two dimensional simulations using an algebraic stress turbulence
model (ASM) were in better agreement with the experimental data than two and three
dimensional simulations using a k - ɛ turbulence model in the wall jet region. A wall jet growth rate was found to be 54% higher than a wall jet in stagnant surroundings due to the enclosure boundaries.

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