The ultrasonic velocity profile measurement of flow structure in the near field of a square free jet |
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Authors: | Y Inoue S Yamashita K Kondo |
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Institution: | (1) Department of Mechanical and Systems Engineering Gifu University, Gifu 501-1193, Japan e-mail: efd@cc.gifu-u.ac.jp Tel.: +81-58-293-2527; +81-58-230-1892, JP;(2) Department of Mechanical Engineering Suzuka National College of Technology Shiroko, Suzuka, Mie 510–0294, Japan, JP |
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Abstract: | Coherent structures in the near field of a three-dimensional jet have been investigated. Experiments were carried out for
a free jet issuing from a square nozzle using a water channel. Instantaneous velocity profiles were obtained in the axial
and radial directions by using an ultrasonic velocity profile (UVP) monitor. Axial variations of dominant time-scales of vortex
structures were examined from one-dimensional wavelet spectra. Wavenumber-frequency spectra were calculated by two-dimensional
Fourier transform along the axial direction in a mixing layer, and it was found that a convective velocity of flow structures
was nearly constant independently of their scales in space and time. Coherent structures in the axial direction were investigated
in terms of proper orthogonal decomposition (POD). Eigenfunctions are similar to a sinusoidal wave, and reconstructed velocity
fields by the lower-order and higher-order POD modes demonstrate large-scale and smaller-scale coherent structures, respectively.
Received: 8 May 2000/Accepted: 23 January 2001 Published online: 29 November 2001 |
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