Fluctuating Velocity-Pressure Field Structure in a Round Jet Turbulent Mixing Region

Nithianandan, C.K.

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https://hdl.handle.net/2142/67791 Copy

Description

Title

Fluctuating Velocity-Pressure Field Structure in a Round Jet Turbulent Mixing Region

Author(s)

Nithianandan, C.K.

Issue Date

1980

Department of Study

Nuclear Engineering

Discipline

Nuclear Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Engineering, Nuclear
• Energy

Language

eng

Abstract

• An experimental study of turbulent mixing has been conducted to provide detailed insight regarding the turbulent transport processes, especially those involving pressure. The investigation was conducted in the mixing region of a 6.35 cm diameter, isothermal, stationary jet having an exit velocity of 91.4 m/s.
• The study involved the following related parts: (1) measurements of single-point pressure-velocity correlations and estimation of the error involved in these correlations due to the velocity contamination of the pressure probe; (2) measurements of the three velocity components simultaneously, in order to obtain higher order velocity correlations and to verify the similarity of these correlations so that similarity assumptions can be used in the turbulent kinetic energy balance and in turbulent modeling work; (3) estimation of two-dimensional velocity vector patterns representing the large-scale coherent structures from the pressure-velocity correlation measurements using the linear estimation theory; (4) review and experimental verification of velocity and pressure spectra modeling theory based on dimensional analysis and extension of this study to include cross spectra of shear stress and pressure-velocity correlations; and (5) verification of the turbulent kinetic energy balance.
• Multi-channel hot wire anemometry techniques were used to study the turbulent characteristics of the velocity field. Both X-probes and a special 3-wire sensor probe were used in conjunction with a bleed type pressure transducer to obtain the velocity components and the pressure fluctuations simultaneously. The X-probe-PT (= pressure transducer) data were analyzed, assuming low intensity turbulence, using both analog and digital signal processing. The 3-wire-PT data were analog-to-digital converted and digitally analyzed on an IBM 360 computer using the analytical response equations for inclined hot-wires accurate to third-order velocity correlation terms.
• All of the correlations in the driven mixing region are found to be self similar. This observation helped considerably in obtaining the turbulent kinetic energy balance and in representing other aspects of the turbulent field, such as low wavenumber spectral similarity. The experimental verification of the turbulent kinetic energy balance is found to be satisfactory, and the mean error across the mixing region is about 5% of the sum of the absolute values of the terms in the kinetic energy equation. From these results, it is estimated that the error in the measured pressure-velocity correlation is about 9%.
• The single component spectra of pressure and velocity are found to agree well with the results obtained using dimensional analysis. The dimensional analysis approach is extended to the cross spectra of shear stress and pressure-velocity correlations. The measured results are found to agree well with the theoretical results. In the inertial subrange, the magnitude of the pressure-radial velocity spectra, along the centerline of mixing at four and five diamenters from the exit of the jet are found to agree well with the exact pressure-velocity spectra from theory.

Graduation Semester

1980

Type of Resource

text

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http://hdl.handle.net/2142/67791

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