Open Access

ARTICLE

Effects of Flow Pulsing on Passive Scalar Mixing in a Turbulent Round Jet

A. Benaissa¹, I. Yimer²

1 Royal Military College of Canada, Kingston Ontario Canada K7K 7B4, benaissa@rmc.ca
2 GTL-IAR. National Research Council, Ottawa, Ontario Canada

Fluid Dynamics & Materials Processing 2010, 6(2), 203-218. https://doi.org/10.3970/fdmp.2010.006.203

Abstract

This work presents a study on the effect of pulsing on a jet flow. Pulsing is used to modify jet inlet conditions with the objective of improving mixing. In this experimental work, a jet was slightly heated so that temperature could be considered as a passive scalar. The spectral behaviour of velocity and the passive scalar temperature was analyzed along the jet axis with and without pulsing. Low frequency pulsing (f/fS< 0.05 fSthe Strouhal frequency) modifies the spectral composition of the velocity at the jet exit, but it does not affect the asymptotic profile reached in the fully developed region of the jet at approximately x/d = 30. The lower frequency pulsations travel far downstream and stay visible in the fully developed region on both the velocity and temperature spectra. This pulsing affects slightly the scalar spectral composition at the jet exit for only the highest frequency used (f/fS= 0.04 (40 Hz) to 0.05 (80 Hz)). This indicates that mixing is improved since the change reflects mixing the main flow with the surrounding airflow. Also, the presence of low pulsing frequencies far downstream indicates the effect produced at the jet exit lasts into the far field.

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Keywords

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