Buoyancy Profile Inhibition of Turbulence in Nearly Vertical Bubbly Shear Flow
We report mea.sUICJD.CD.ts of two-dimensional (B/D::S) fully tw:bulent and developed duct flows (overall length/depth. IlD=60; D-based Reynolds number Re>104) for inclinations to 30 degrees from vertical at low voidagcs (<5% sectional average) representative of disperse regime using tap water...
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| Format: | Article |
| Language: | English |
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National University of Sciences and Technology, Islamabad
2008-12-01
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| Series: | NUST Journal of Engineering Sciences |
| Online Access: | https://journals.nust.edu.pk/index.php/njes/article/view/27 |
| _version_ | 1797854235038056448 |
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| author | Khairuddin Sanaullah N. H. Thomas |
| author_facet | Khairuddin Sanaullah N. H. Thomas |
| author_sort | Khairuddin Sanaullah |
| collection | DOAJ |
| description |
We report mea.sUICJD.CD.ts of two-dimensional (B/D::S) fully tw:bulent and developed duct flows (overall length/depth. IlD=60; D-based Reynolds number Re>104) for inclinations to 30 degrees from vertical at low voidagcs (<5% sectional average) representative of disperse regime using tap water bubbles ( 4-6 mm) and smaller bubbles (2 mm) stabilised in ionic solution. Pitot and static probe instrumentation, primitive but validated, provided adequate (10% local value) discrimination of main aspects of Che mean velocity and voidage profiles at representative streamwise station i.e IlD =40. Our results can be divided into three categories of behavionr. For vertical flow (0 degrees) the evidence is inconclusive as to whether bubbles are preferentially trapped within the wall-layer as found in some, may be most, earlier experimental work. Thus the 4 mm bubbles showed indication of voidage retention but Che 2 mm bubbles did not. For nearly vertical flow (5 degrees) there was pronounced profiling of voidage especially with 4 mm bubbles but the Transvm e transport was not suppressed sufficiently to induce any obvious layering. In Chis context, we also refer to similarities wieh previous work on one-phase vertical and nearly vertical mixed convection flows displaying buoyancy inhibited mean shear turbulence. However, with inclined flow (10+ degrees) a distinctively layered pattem was invariably manifested in which voidage confinement increased with increasing inclination. In this paper we address flow behaviour at near vertical conditions.
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| first_indexed | 2024-04-09T20:02:35Z |
| format | Article |
| id | doaj.art-e25405520f5746eea69a37bde84910c3 |
| institution | Directory Open Access Journal |
| issn | 2070-9900 2411-6319 |
| language | English |
| last_indexed | 2024-04-09T20:02:35Z |
| publishDate | 2008-12-01 |
| publisher | National University of Sciences and Technology, Islamabad |
| record_format | Article |
| series | NUST Journal of Engineering Sciences |
| spelling | doaj.art-e25405520f5746eea69a37bde84910c32023-04-02T23:24:36ZengNational University of Sciences and Technology, IslamabadNUST Journal of Engineering Sciences2070-99002411-63192008-12-011110.24949/njes.v1i1.27Buoyancy Profile Inhibition of Turbulence in Nearly Vertical Bubbly Shear FlowKhairuddin SanaullahN. H. Thomas We report mea.sUICJD.CD.ts of two-dimensional (B/D::S) fully tw:bulent and developed duct flows (overall length/depth. IlD=60; D-based Reynolds number Re>104) for inclinations to 30 degrees from vertical at low voidagcs (<5% sectional average) representative of disperse regime using tap water bubbles ( 4-6 mm) and smaller bubbles (2 mm) stabilised in ionic solution. Pitot and static probe instrumentation, primitive but validated, provided adequate (10% local value) discrimination of main aspects of Che mean velocity and voidage profiles at representative streamwise station i.e IlD =40. Our results can be divided into three categories of behavionr. For vertical flow (0 degrees) the evidence is inconclusive as to whether bubbles are preferentially trapped within the wall-layer as found in some, may be most, earlier experimental work. Thus the 4 mm bubbles showed indication of voidage retention but Che 2 mm bubbles did not. For nearly vertical flow (5 degrees) there was pronounced profiling of voidage especially with 4 mm bubbles but the Transvm e transport was not suppressed sufficiently to induce any obvious layering. In Chis context, we also refer to similarities wieh previous work on one-phase vertical and nearly vertical mixed convection flows displaying buoyancy inhibited mean shear turbulence. However, with inclined flow (10+ degrees) a distinctively layered pattem was invariably manifested in which voidage confinement increased with increasing inclination. In this paper we address flow behaviour at near vertical conditions. https://journals.nust.edu.pk/index.php/njes/article/view/27 |
| spellingShingle | Khairuddin Sanaullah N. H. Thomas Buoyancy Profile Inhibition of Turbulence in Nearly Vertical Bubbly Shear Flow NUST Journal of Engineering Sciences |
| title | Buoyancy Profile Inhibition of Turbulence in Nearly Vertical Bubbly Shear Flow |
| title_full | Buoyancy Profile Inhibition of Turbulence in Nearly Vertical Bubbly Shear Flow |
| title_fullStr | Buoyancy Profile Inhibition of Turbulence in Nearly Vertical Bubbly Shear Flow |
| title_full_unstemmed | Buoyancy Profile Inhibition of Turbulence in Nearly Vertical Bubbly Shear Flow |
| title_short | Buoyancy Profile Inhibition of Turbulence in Nearly Vertical Bubbly Shear Flow |
| title_sort | buoyancy profile inhibition of turbulence in nearly vertical bubbly shear flow |
| url | https://journals.nust.edu.pk/index.php/njes/article/view/27 |
| work_keys_str_mv | AT khairuddinsanaullah buoyancyprofileinhibitionofturbulenceinnearlyverticalbubblyshearflow AT nhthomas buoyancyprofileinhibitionofturbulenceinnearlyverticalbubblyshearflow |