Local wall shear stress and interface behavior of adiabatic air-water flows in rectangular ducts
| dc.contributor.advisor | Sridhar, K. R. | en_US |
| dc.contributor.author | Gottmann, Matthias, 1964- | |
| dc.creator | Gottmann, Matthias, 1964- | en_US |
| dc.date.accessioned | 2013-04-18T09:47:24Z | |
| dc.date.available | 2013-04-18T09:47:24Z | |
| dc.date.issued | 1997 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10150/282445 | |
| dc.description.abstract | An experiment was designed and built to study vertical annular air-water flows in a channel with a rectangular cross section with no heat transfer. Flush-wire electrical conductivity probes were theoretically analyzed to demonstrate their potential to accurately measure liquid film thickness in the experiment with high temporal and spatial resolution. Flush-wire probes were then successfully implemented and film thickness measurements obtained. From theoretical analysis, the suitability of micromachined hot film and floating element wall shear stress sensors for measurements of wall shear stress in the annular flow was investigated. A microfabricated hot film wall shear stress sensor was subsequently packaged and installed in the experiment, where it provided wall shear stress measurements with high temporal and spatial resolution. After the implementation of these new measurement techniques, a large suite of test cases was run and data for film thickness and wall shear stress acquired. A statistical analysis of the film thickness data indicates the existence of two distinct wave regimes, ripple waves and disturbance waves, within the annular flow regime. Spectral decomposition of film thickness and wall shear stress data demonstrates the existence of dominant frequencies in the wave spectrum and an exponential decay of wave amplitudes at high frequencies indicative of a force balance between capillary and momentum forces. Wave velocities were determined from cross correlations which again provided evidence of different types of waves each with different wave velocities and spatial extensions. A semi-analytical model for wave velocities as a function of superficial Reynolds numbers was validated and improved. The improved model gives an accurate prediction for wave velocities and is based on physical arguments representing the appropriate length scales in annular flow. The experimental results and data analysis provide a new perspective of annular two-phase flows in a channel with a rectangular cross section. | |
| dc.language.iso | en_US | en_US |
| dc.publisher | The University of Arizona. | en_US |
| dc.rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. | en_US |
| dc.subject | Engineering, Aerospace. | en_US |
| dc.subject | Engineering, Mechanical. | en_US |
| dc.title | Local wall shear stress and interface behavior of adiabatic air-water flows in rectangular ducts | en_US |
| dc.type | text | en_US |
| dc.type | Dissertation-Reproduction (electronic) | en_US |
| thesis.degree.grantor | University of Arizona | en_US |
| thesis.degree.level | doctoral | en_US |
| dc.identifier.proquest | 9806837 | en_US |
| thesis.degree.discipline | Graduate College | en_US |
| thesis.degree.discipline | Aerospace and Mechanical Engineering | en_US |
| thesis.degree.name | Ph.D. | en_US |
| dc.description.note | This item was digitized from a paper original and/or a microfilm copy. If you need higher-resolution images for any content in this item, please contact us at repository@u.library.arizona.edu. | |
| dc.identifier.bibrecord | .b37557130 | en_US |
| dc.description.admin-note | Original file replaced with corrected file October 2023. | |
| refterms.dateFOA | 2018-09-05T18:09:22Z | |
| html.description.abstract | An experiment was designed and built to study vertical annular air-water flows in a channel with a rectangular cross section with no heat transfer. Flush-wire electrical conductivity probes were theoretically analyzed to demonstrate their potential to accurately measure liquid film thickness in the experiment with high temporal and spatial resolution. Flush-wire probes were then successfully implemented and film thickness measurements obtained. From theoretical analysis, the suitability of micromachined hot film and floating element wall shear stress sensors for measurements of wall shear stress in the annular flow was investigated. A microfabricated hot film wall shear stress sensor was subsequently packaged and installed in the experiment, where it provided wall shear stress measurements with high temporal and spatial resolution. After the implementation of these new measurement techniques, a large suite of test cases was run and data for film thickness and wall shear stress acquired. A statistical analysis of the film thickness data indicates the existence of two distinct wave regimes, ripple waves and disturbance waves, within the annular flow regime. Spectral decomposition of film thickness and wall shear stress data demonstrates the existence of dominant frequencies in the wave spectrum and an exponential decay of wave amplitudes at high frequencies indicative of a force balance between capillary and momentum forces. Wave velocities were determined from cross correlations which again provided evidence of different types of waves each with different wave velocities and spatial extensions. A semi-analytical model for wave velocities as a function of superficial Reynolds numbers was validated and improved. The improved model gives an accurate prediction for wave velocities and is based on physical arguments representing the appropriate length scales in annular flow. The experimental results and data analysis provide a new perspective of annular two-phase flows in a channel with a rectangular cross section. |
