Flow and mixing characteristics of dual parallel plane jets subject to acoustic excitation

The current study reports numerical analysis of turbulent jets. Effects of various parameters on the characteristics of two-dimensional turbulent plane parallel and offset jets are investigated. The emphasis is put on the effect of the wall angle and nozzle width on the location merging and the combining points. The flowfield under consideration are two-parallel plane jets and offset jets issued from plane wall. Four angles and three values of the nozzle width are used. Also, different values of Reynolds number between 9000 and 39000 have been examined. It is noted that the wall angle and the nozzle width linearly affect the location of the merging and the combining points, while Reynolds number plays no role in their location. The effect of the wall angle on the reattachment point is found to be non linear.

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Experimental investigation of five parallel plane jets with variation of Reynolds number and outlet conditions

EPJ Web of Conferences ◽

10.1051/epjconf/201818002018 ◽

2018 ◽

Vol 180 ◽

pp. 02018 ◽

Cited By ~ 2

Author(s):

Tomas Daubner ◽

Jens Kizhofer ◽

Mircea Dinulescu

Keyword(s):

Experimental Investigation ◽

Reynolds Number ◽

Near Field ◽

Parallel Plane ◽

Nozzle Geometry ◽

Channel Height ◽

Equivalent Diameter ◽

Free Atmosphere ◽

Single Plane ◽

Plane Jets

This article describes an experimental investigation in the near field of five parallel plane jets. The study applies 2D Particle Image Velocimetry (PIV) for ventilated and unventilated jets, where ventilated means exiting into a duct with expansion ratio 3.5 and unventilated means exiting to the free atmosphere. Results are presented for Reynolds numbers 1408, 5857 and 10510. The Reynolds number is calculated for the middle channel and is based on the height of the nozzle (channel) equivalent diameter 2h. All characteristic regions of the methodology to describe multiple interacting jets are observed by the PIV measurements - converging, merging and combined. Each of the five parallel channels has an aspect ratio of 25 defined as nozzle width (w) to height (h). The channels have a length of 185 times the channel height guaranteeing a fully developed velocity profile at the exit from the channel. Spacing between the single plane jets is 3 times the channel height. The near field of multiple mixing jets is depended on outlet nozzle geometry. Blunt geometry of the nozzle was chosen (sudden contraction).

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Modulating flow and mixing characteristics of an inclined jet in crossflow at a large backward inclination angle by acoustic excitation

International Journal of Mechanical Sciences ◽

10.1016/j.ijmecsci.2021.106708 ◽

2021 ◽

pp. 106708

Author(s):

Sukendro Broto Sasongko ◽

Rong Fung Huang ◽

Ching Min Hsu

Keyword(s):

Inclination Angle ◽

Acoustic Excitation ◽

Jet In Crossflow ◽

Mixing Characteristics

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Interaction of two parallel plane jets of different velocities

Journal of Visualization ◽

10.1007/bf03181586 ◽

2004 ◽

Vol 7 (2) ◽

pp. 135-142 ◽

Cited By ~ 39

Author(s):

N. Fujisawa ◽

K. Nakamura ◽

K. Srinivas

Keyword(s):

Parallel Plane ◽

Plane Jets

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Comparisons of Flow and Mixing Characteristics between Unforced and Excited Elevated Transverse Jets

Journal of Mechanics ◽

10.1017/jmech.2013.74 ◽

2013 ◽

Vol 30 (1) ◽

pp. 87-96 ◽

Cited By ~ 2

Author(s):

C. M. Hsu ◽

R. F. Huang

Keyword(s):

Velocity Field ◽

Momentum Flux ◽

High Speed ◽

Symmetry Plane ◽

Image Processing Technique ◽

Large Momentum ◽

Acoustic Excitation ◽

Recirculation Bubble ◽

Transverse Jet ◽

Mixing Characteristics

ABSTRACTThe influences of acoustic excitation on the velocity field and mixing characteristic of a jet in cross-flow were investigated in a wind tunnel. The acoustic excitation waves at resonance Strouhal number were generated by a loudspeaker. The time-averaged velocity field and streamlines of the excited elevated transverse jet in the symmetry plane were measured by a high-speed particle image velocimetry. The visual penetration height and spread width were obtained by using an image processing technique. The dispersion characteristics were obtained from the tracer-gas concentration measurement. The results showed that the streamline pattern of the non-excited transverse jet was significantly modified by the acoustic excitation—the bent streamlines evolved from the jet exit escalated and the vortex rings in the jet and tube wakes and the recirculation bubble in the jet wake disappeared. The time-averaged velocity distributions revealed that the excited transverse jet produces large momentum in the up-shooting direction so that the velocity trajectories were located at levels higher than those of the non-excited one. The mixing characteristics, which include the visual penetration height, spread width, and dispersion, were drastically improved by the acoustic excitation due to the changes in the flow structures. The excited transverse jet characterized at larger jet-to-crossflow momentum flux ratios presented larger improvement in the mixing characteristics than at lower jet-to-crossflow momentum flux ratios.

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Applicability of Reichardt's Hypothesis to the Prediction of Velocity Field of Multiple Parallel Plane Jets

Journal of Mechanics ◽

10.1017/s1727719100003117 ◽

2010 ◽

Vol 26 (2) ◽

pp. N17-N22

Author(s):

A. Nasr ◽

J. Lai

Keyword(s):

Velocity Field ◽

Parallel Plane ◽

Center Line ◽

Lateral Direction ◽

Free Jet ◽

Plane Jets ◽

The Individual ◽

Theoretical Results ◽

Good Agreement ◽

Made In

AbstractIn this paper the velocity distribution for multiple parallel plane jets based on the superposition of Reichardt's solution for single free jet is derived. The extend of the applicability of Reichardt's hypothesis to prediction of multiple parallel plane jets is examined. Both ventilated and unventilated two parallel plane jets data published in the literature and obtained for this study were used for comparisons with the theoretical results obtained from Reichardt's hypothesis. LDA measurements of mean streamwise velocities and turbulence characteristics of an array of 5 parallel plane jets were also made in order to establish the conditions under which this heuristic approach is valid. Results show that provided the pressure gradient in the lateral direction is small and hence the deflection of the individual jet center line is small, there is a good agreement between experimental results and predictions based on Reichardt's hypothesis for multiple parallel plane jets.

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