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Reynolds number effect on flow characteristics of surface single and twin jets

Author(s): Mohammad S. Rahman; Mark F. Tachie

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Keywords: Galilean decomposition; particle image velocimetry; Reynolds stress; surface jet; twin jet

Abstract: Turbulent characteristics of single and twin jets interacting with a free surface were investigated using a particle image velocimetry system. The exit Reynolds numbers were varied from 2300 to 11,900 at an offset height of two nozzle widths from the free surface. Galilean decomposition showed, irrespective of the Reynolds number, the free surface weakens the instantaneous spanwise vorticity. The jet attachment point to the free surface was located and found to be sensitive at lower Reynolds number. Scaling parameter for the surface velocity defect and turbulence intensities were explored for the single and twin jets. The mixing characteristics of the jets were investigated using maximum velocity decay rate, spread rate and entrainment coefficient, and results showed that the shear layer away from the free surface developed downstream like a free jet. One-dimensional profiles of mean velocity and Reynolds stresses were independent of Reynolds number except in the location of the attachment point.


Year: 2019

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