Visualization of coherent structure in scalar fields of unsteady jet flows with interferometric tomography and proper orthogonal decomposition |
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Authors: | B J Pelliccia-Kraft D W Watt |
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Institution: | (1) Mechanical Engineering Department, University of New Hampshire, Durham, NH 03824, USA, US |
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Abstract: | Proper orthogonal decomposition (POD) is a method of examining spatial coherence in unsteady flow fields from an ensemble
of multidimensional measurements. When applied to experimental data, the proper orthogonal decomposition is generally restricted
to data sets with low spatial resolution. This is because of the inherent difficulties in generating an ensemble of measurements
that contain a large number of data points. In this paper, a system for obtaining a large ensemble of three-dimensional scalar
measurements using interferometric tomography is presented. The proper orthogonal decomposition is applied in three spatial
dimensions to experimental data of two jet-like flows. The coherent structure present in the near field of a neutrally buoyant,
helium–argon jet and the far field of a buoyant helium jet into air is visualized. The POD results of the helium–argon jet
clearly reveal the breakdown region of a sequence of vortex rings and a large-scale flapping motion in the jet far field.
The POD of the buoyant helium jet shows a number of competing modes with varying degrees of helicity.
Received: 14 January 2000/Accepted: 26 September 2000 |
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