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Research Papers: Fundamental Issues and Canonical Flows

Experimental Investigations of Transfer Phenomena in a Confined Plane Turbulent Impinging Water Jet

[+] Author and Article Information
Amine Koched

Michel Pavageau

Ecole des Mines de Nantes Département Systèmes Energétiques et Environnement (DSEE) GEPEA CNRS UMR 6144, 4 rue Alfred Kastler BP20722, FR-44307 Nantes, Francemichel.pavageau@mines-nantes.fr

Fethi Aloui1

Ecole des Mines de Nantes Département Systèmes Energétiques et Environnement (DSEE) GEPEA CNRS UMR 6144, 4 rue Alfred Kastler BP20722, FR-44307 Nantes, France;  Université de Nantes Faculté des Sciences et des Techniques Département de Physique 2, rue de la Houssiniere BP92208, FR-44322 Nantes, France e-mail: fethi.aloui@univ-nantes.fr

1

Corresponding author.

J. Fluids Eng 133(6), 061204 (Jun 16, 2011) (13 pages) doi:10.1115/1.4004090 History: Received November 10, 2010; Revised April 28, 2011; Published June 16, 2011; Online June 16, 2011

In this study, we are interested in the hydrodynamics of impinging plane jets. Plane jets are widely used in ambience separation in HVAC, fire safety, food process engineering, cooling of electronic components etc. Despite their important industrial applications, plane jets have not been studied as extensively as axisymmetric jets. Plane jets exhibit different kind of instabilities stemming from either streamlines with strong curvature in the impingement region or inflection points in the transverse profile of the streamwise component velocity in the lateral mixing layers. Previous works in the GEPEA laboratory were performed on these flows. These works and the majority of the studies reported in the literature deal with turbulent air jets in various configurations. Very little studies have been done on water impinging jets. Taking into account the fact that the viscosity of water is smaller than air, at the same Reynolds number, it is easier to detect phenomena such as vortices. Phenomena can be observed at lower velocities making it possible to record signals with standard frequency bandwidths. This makes it easier also to do a Lagrangian tracking of vortices. We specially focused our study on the impinging zone of the jet. The dynamics of the impinging zone has not formed the subject of numerous studies. There were no studies that characterize the vortices at the impinging region of water jets in terms of size, centre position, vortex intensity, convection velocities, eccentricity, statistical distribution and turbulent length and time scales. Consequently, a confined water plane jet impinging a flat plate was studied using standard and high speed PIV (Particle Image Velocimetry). We used POD decomposition for filtering PIV data. Then, we applied the λ2 criterion to the recorded velocity fields to detect and characterize the vortices at the impingement. A statistical analysis was then performed. Turbulent length scales, time scales and convection velocities of eddies occurring at the impingement were determined using two point space time correlations. The obtained results were correlated to the dynamics and geometric properties of the jet. A wide range of Reynolds numbers is considered: 3000, 6000, 11000 and 16000. The corresponding results are presented in this paper.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 9

Variation of u'v'−/Vmax2 with Re number; H/e = 10

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Figure 10

PIV measurement in a plane parallel to the impingement

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Figure 11

11th spatial mode ( Φ11)

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Figure 12

11th spatial mode ( Φ11)

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Figure 13

(a) Tangential component velocity profile within the core of a vortex; (b) Radial directions considered for diameter estimation of the vortex

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Figure 14

Number of vortices detected for each plane and Reynolds number considered

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Figure 15

Percentage of counter-clockwise and clockwise vortices

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Figure 16

Probability density function of the mean diameter of vortices in the different planes: (a) P1 ; (b) P2 ; (c) P3 ; (d) P-2 ; (e) P-3

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Figure 17

Probability density function of eccentricity of vortices (plane P1 at the centre of the jet)

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Figure 18

Recording parameters for high-speed PIV acquisitions (f = 350 Hz)

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Figure 19

Reference position considered for space time two points correlations

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Figure 20

Space-time correlation functions for selected tests (8 positions at L5  = 150 mm) (a) Re = 1000; (b) Re = 3000; (c) Re = 6000; (d) Re = 11,000; (e) Re = 16,000

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Figure 21

Length scale function of the Reynolds number

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Figure 22

Convection velocity at the impingement of the jet function of the Reynolds number

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Figure 23

Time scales of the detected vortices at the impingement

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Figure 8

Streamlines at the transverse plane of the jet (Re = 16,000)

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Figure 7

Turbulent intensities at the nozzle (a) Iu (b) Iv

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Figure 6

Velocity profiles of the longitudinal velocity component at the nozzle

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Figure 5

Recording parameters for standard PIV acquisitions (f = 15 Hz)

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Figure 4

Position of the planes considered for PIV measurements

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Figure 3

Measurement planes considered for PIV technique

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Figure 2

Characteristic distances of the jet

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Figure 1

Experimental setup

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