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Research Papers

Characterization of Pulsating Submerged Jet—A Particle Image Velocimetry Study

[+] Author and Article Information
Harekrishna Yadav

Department of Mechanical Engineering,
Indian Institute of Technology Bombay,
Powai, Mumbai 400076, India
e-mail: krishna.04p@gmail.com

Atul Srivastava

Department of Mechanical Engineering,
Indian Institute of Technology Bombay,
Powai, Mumbai 400076, India
e-mail: atulsr@iitb.ac.in

Amit Agrawal

Department of Mechanical Engineering,
Indian Institute of Technology Bombay,
Powai, Mumbai 400076, India
e-mail: amit.agrawal@iitb.ac.in

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received April 30, 2014; final manuscript received March 6, 2015; published online November 11, 2015. Assoc. Editor: Suman Chakraborty.

J. Thermal Sci. Eng. Appl 8(1), 011014 (Nov 11, 2015) (9 pages) Paper No: TSEA-14-1108; doi: 10.1115/1.4030813 History: Received April 30, 2014

An experimental investigation has been performed to determine the flow characteristics of an axisymmetric submerged water jet with superimposed periodically oscillating flow. The objective of the study is to quantify in detail the near field of a pulsating jet using the particle image velocimetry (PIV) technique. The amplitude and frequency of oscillations are varied separately and the effect of each parameter is determined for a range of Reynolds numbers (ReD = 1602, 2318, and 3600). The experimental results indicate that for a given Reynolds number and amplitude, with an increase in the frequency of pulsation, the vortex formation shifts toward the nozzle exit. The number of vortices also increases with an increase in the jet pulsation frequency. Broadening of the jet and shortening of the potential core length are also observed. This indicates that mixing with the surrounding fluid is higher with pulsating jet even at relatively low Reynolds numbers. It is observed that frequency up to a critical frequency helps increase entrainment of the surrounding fluid. An upper critical frequency beyond which pulsation does not affect the entrainment is also determined. These results should eventually lead to a better understanding of the physical phenomena responsible for enhanced heat transfer rates in the presence of pulsating jets.

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Figures

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Fig. 1

(a) Schematic diagram and (b) picture of the experimental setup employed for the measurements

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Fig. 2

(a) Time series of velocity at the exit of the center of the nozzle for Re = 1602, f = 1 Hz, A = 10% and (b) zoomed view of (a) showing the definition of various parameters employed

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Fig. 3

Instantaneous velocity vectors at Re = 2318 and A = 12%: (a) steady jet, (b) f = 0.5 Hz, (c) f = 1 Hz, (d) f = 2 Hz, and (e) f = 3 Hz

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Fig. 4

Instantaneous velocity vectors at Re = 2318, f = 1 Hz, and A = 6%

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Fig. 5

Three successive instantaneous velocity vectors at Re = 2318, f = 2 Hz, and A = 12%: (a) instantaneous velocity vector at t = t1 s, (b) instantaneous velocity vector at t = (t1 + Δt) s, and (c) instantaneous velocity vector at t = (t1 +2Δt) s

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Fig. 6

Vortex location at Re = 1602, f = 0.5 Hz, and A = 6%: (a) t = 0 s, (b) Δt = 0.2 s, and (c) Δt = 0.4 s

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Fig. 7

Radial variation of instantaneous vorticity for (a) steady jet and (b) pulse jet at f = 3 Hz, A = 8%, and Re = 3600

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Fig. 8

Characterization of steady and pulsating jet at Re = 2318 and A = 12%: (a) variation of centerline velocity, (b) widening of jet with axial distance, and (c) variation of turbulence intensity with axial distance

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Fig. 9

Effect of pulsation amplitude at Re = 1602

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Fig. 10

Variation of centerline velocity with axial distance: (a) Re = 1602, A = 6% and (b) Re = 2318, A = 6%

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