Turbulent structure during transition to self-similarity in a round jet |
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Authors: | T H Weisgraber D Liepmann |
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Institution: | (1) Department of Mechanical Engineering University of California, Berkeley Berkeley, CA 94720, USA, US |
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Abstract: | The developing turbulent region of a round jet was investigated using an improved implementation of digital particle image
velocimetry (DPIV). The two-dimensional flow field in planes normal and parallel to the axial velocity was measured at locations
between 15 and 30 diameters downstream, for two Reynolds numbers of 5500 and 16,000. The study consisted of instantaneous
snapshots of the velocity and vorticity fields as well as measurements of velocity correlations up to third order. In this
regime, the Reynolds number had a significant effect on both the instantaneous flow structure and the profiles of mean velocity
across the jet. Coherent streamwise structures were present in the jet core for the lower Reynolds number. Additional structures
whose evolution was governed by time scales two orders of magnitude larger than the convective scale inside the jet were observed
in the entrainment field. The velocity correlations provided further support for the validity of DPIV turbulence measurements.
The data was consistent with the equations of motion and momentum was conserved. DPIV measurements of turbulent kinetic energy
components agreed with the hot-wire measurements of previous studies.
Received: 27 November 1996/Accepted: 14 July 1997 |
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