University of Illinois Urbana-Champaign

Fluctuating pressure and velocity fields in near field of round jet

Chang, Paul; Adrian, Ronald J.; Jones, Barclay G.

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https://hdl.handle.net/2142/112215

Description

Title
Fluctuating pressure and velocity fields in near field of round jet
Author(s)
  • Chang, Paul
  • Adrian, Ronald J.
  • Jones, Barclay G.
Issue Date
1985-11
Keyword(s)
  • Pressure Velocity Correlation
  • Triple Wire Anemometer Probe
  • Colling Velocity
  • Round Jet
  • Near Field
Abstract
A new analysis algorithm for analyzing signals of a triple-wire anemometer probe is presented which describes the performance of the hot-wire probe and shows the ambiguity in interpretation of the three effective colling velocities for a range of flow vector directions. Jorgensen's (1971) cooling law for cylinders inclined to the flow vector is adopted. Inverted velocity vectors are multiple, but a uniqueness domain is defined within which the vector coinciding with the true velocity vector can be singled out. Samples of linearized voltages were taken in the turbulent shear layer of a 6.35 cm diameter jet and analyzed by the algorithm. The results support the methodology of the algorithm. The mechanisms that cause some of the samples to reside outside the realizabilty domain are discussed. A dynamic test in terms of pressure-velocity correlation in an unsteady irrotational flow was performed for the bleed-type pressure transducer. Pressure-velocity correlations calculated from the unsteady Bernoulli equation agree closely with direct measurements with the pressure transducer has properly response. The triple-wire probe together with the pressure transducer were used to investigate the shear layer of a round jet. Comparison between the triple-wire and a regular X-wire data shows good agreement in low turbulence level regions. Experimental results support the existence of an apparent self-preserving zone between 3 X/D < 5. Single-point pressure-velocity correlations spanning the shear layer show that pressure is generated by a combination of the irrotational Bernoulli effect and rotational effects. The pressure fluctuations are correlated with relatively local velocity field behavior. P-u' cross spectra exhibit power law behavior between k18/3 and k1-2 but closer to k1-8/3 power law. Data support a simple gradient transport model for the transport of pressure energy. Two-point pressure-velocity spatial-time correlations were measured in detail with stationary velocity probe and a moving pressure probe. Conditional averages and linear estimation results agree very well. Conditional pressure fields show the vortex structure with a wavelength about 1.1 nozzle diameters.
Publisher
Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report Name or Number
  • TAM R 475
  • 1985-6006
ISSN
0073-5264
Type of Resource
text
Language
eng
Permalink
http://hdl.handle.net/2142/112215
Sponsor(s)/Grant Number(s)
TSI, Inc., St Paul Minn 85/11
Copyright and License Information
Copyright 1985 Board of Trustees of the University of Illinois

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Technical Reports - Theoretical and Applied Mechanics (TAM) PRIMARY
TAM technical reports include manuscripts intended for publication, theses judged to have general interest, notes prepared for short courses, symposia compiled from outstanding undergraduate projects, and reports prepared for research-sponsoring agencies.