Studies of Jet Flow in Enclosures

Abstract

<p>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.</p> <p>The impingement ofaxisynunetric jets in a cavity has been examined using<br />flow visualization, laser Doppler anemometry, and numerical simulations. When the<br />flow fIeld was examined under various geometrical and fluid parameters several flow<br />regions were found, depending on the geometrical and fluid parameters. Initially, a<br />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<br />oscillations and the upper limit of fmite oscillations were found to be a function of the<br />nozzle diameter to chamber dimeasion ratio. Although steady numerical simulations<br />predicted the steady flow field well. steady simulations of the oscillating flow field<br />over-predicted the peak axial velocities. The oscillating flow field is considered to be<br />a class of self-sustaining oscillations where instabilities in the jet shear layer are<br />amplified because of feed back from pressure disturbances in the impingement region.</p> <p>The turbulent wall jet in a cavity has been studied using flow visualization,<br />laser Doppler anemometry (LDA), particle streak velocimetry (PSV) and numerical<br />simulations. Instantaneous PSV measurements agreed well with time averaged LDA measurements. Two dimensional simulations using an algebraic stress turbulence<br />model (ASM) were in better agreement with the experimental data than two and three<br />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.</p>