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On the convective velocity of large-scale structures in compressible axisymmetric jets

Thurow, Brian S
http://rave.ohiolink.edu/etdc/view?acc_num=osu1102000184

Abstract Details

2005, Doctor of Philosophy, Ohio State University, Mechanical Engineering.
The role of compressibility on the convective velocity of large-scale structures in axisymmetric jets is studied using a home-built pulse burst laser system and newly developed high-repetition rate experimental diagnostics. A pulse burst laser system was designed and constructed with the ability to produce a burst of short duration (10 nsec), high energy (order of 10 -100 mJ/pulse) pulses over a ~150 microsecond period with inter-pulse timing as low as 1 microsecond (1 MHz). The application of the pulse burst laser for flow measurements was investigated through the development of MHz rate flow visualization and MHz rate planar Doppler velocimetry (PDV). MHz rate PDV is a spectroscopic technique that produces 28 time-correlated realizations of the velocity over a plane with a maximum repetition rate of up to 1 MHz and accuracies on the order of 5%. Space-time correlations were used to track structures within the flow field and determine their convective velocity. Data produced using flow visualization images agrees with previous research and indicates a strong departure of the convective velocity from theory. Data produced using velocity data, however, shows starkly different trends and does not produce the same measurements of convective velocity. This difference in measurement is attributed to a misinterpretation of the use of space-time correlation for tracking structures. The presence of a distinct boundary between the mixing layer and the jet core as well as the mixing layer and ambient air in the flow visualization data and some of the velocity data leads to a bias in the measurement. The space-time correlation is found to preferentially follow these boundaries, thus leading to faster and/or slower measurements of convective velocity. For the Mach 2.0 jet, velocity data was obtained with seed particles marking the jet core and the mixing layer, but not the ambient air. This lack of velocity measurements on the low-speed side of the jet’s mixing layer biased the space-time correlation results. An algorithm was developed to extrapolate the velocity into unseeded regions of the flow. Space-time correlation results based on the extrapolated data indicate a convective velocity close to the theoretical value.
Mo Samimy (Advisor)
226 p.
compressibility; compressible free shear layers; experimental fluid mechanics; fluid dynamics; aerodynamic measurement techniques; lasers; high-repetition rate lasers; advanced optical diagnostics; compressible fluid dynamics

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Citations

  • Thurow, B. S. (2005). On the convective velocity of large-scale structures in compressible axisymmetric jets [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1102000184

    APA Style (7th edition)

  • Thurow, Brian. On the convective velocity of large-scale structures in compressible axisymmetric jets. 2005. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1102000184.

    MLA Style (8th edition)

  • Thurow, Brian. "On the convective velocity of large-scale structures in compressible axisymmetric jets." Doctoral dissertation, Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1102000184

    Chicago Manual of Style (17th edition)

osu1102000184
1,436
© 2004, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.