Flow and heat transfer characteristics of blooming jets impinging upon wall using DNS
A single impinging jet exhibits high heat transfer performance around an impingement point on a wall. However, the heat transfer performance deteriorates as it moves away from the impingement point. Consequently, multiple impinging jets are commonly introduced to overcome the shortcomings of a singl...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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The Japan Society of Mechanical Engineers
2020-03-01
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| Series: | Journal of Fluid Science and Technology |
| Subjects: | |
| Online Access: | https://www.jstage.jst.go.jp/article/jfst/15/2/15_2020jfst0010/_pdf/-char/en |
| _version_ | 1818966064048898048 |
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| author | Kentaro ECHIGO Koichi TSUJIMOTO Toshihiko SHAKOUCHI Toshitake ANDO |
| author_facet | Kentaro ECHIGO Koichi TSUJIMOTO Toshihiko SHAKOUCHI Toshitake ANDO |
| author_sort | Kentaro ECHIGO |
| collection | DOAJ |
| description | A single impinging jet exhibits high heat transfer performance around an impingement point on a wall. However, the heat transfer performance deteriorates as it moves away from the impingement point. Consequently, multiple impinging jets are commonly introduced to overcome the shortcomings of a single jet: inhomogeneous heat distribution on the wall and a narrow heating area. However, inhomogeneous heat transfers still occur. Therefore, a new jet control is required to improve the uniformity of heat transfer. Meanwhile, blooming jets are produced by appropriate combinations of axial and helical excitations at the nozzle exit. Using appropriately selected excitations, a jet can split into two separate jets (bifurcating jet) or spread into a shower of toroidal vortex rings. Blooming jets exhibit good performances of mixing and diffusion, suggesting possible applications in flow control. However, studies regarding the heat transfer performance of blooming jets are non-existent. In this study, we conducted direct numerical simulations of blooming jets impinging upon a wall and investigated their flow characteristics and heat transfer performances. As control parameters, the impingement distance (the distance from the nozzle to the wall) and frequency ratio (the axial excitation frequency to the helical frequency) are varied. The vortex structures and velocity magnitude reveals flow modulations due to blooming control. With the time-averaged local Nusselt number, the heat transfer performance of the blooming jets is evaluated quantitatively. Compared with uncontrolled jets, the uniformity of heat transfer of blooming jets is better, suggesting their potential application for leveling the heat transfer of impinging jets. |
| first_indexed | 2024-12-20T13:26:57Z |
| format | Article |
| id | doaj.art-1712297c7a564687b9043489b73e5c8d |
| institution | Directory Open Access Journal |
| issn | 1880-5558 |
| language | English |
| last_indexed | 2024-12-20T13:26:57Z |
| publishDate | 2020-03-01 |
| publisher | The Japan Society of Mechanical Engineers |
| record_format | Article |
| series | Journal of Fluid Science and Technology |
| spelling | doaj.art-1712297c7a564687b9043489b73e5c8d2022-12-21T19:39:15ZengThe Japan Society of Mechanical EngineersJournal of Fluid Science and Technology1880-55582020-03-01152JFST0010JFST001010.1299/jfst.2020jfst0010jfstFlow and heat transfer characteristics of blooming jets impinging upon wall using DNSKentaro ECHIGO0Koichi TSUJIMOTO1Toshihiko SHAKOUCHI2Toshitake ANDO3Department of Mechanical Engineering, Mie UniversityDepartment of Mechanical Engineering, Mie UniversityDepartment of Mechanical Engineering, Mie UniversityDepartment of Mechanical Engineering, Mie UniversityA single impinging jet exhibits high heat transfer performance around an impingement point on a wall. However, the heat transfer performance deteriorates as it moves away from the impingement point. Consequently, multiple impinging jets are commonly introduced to overcome the shortcomings of a single jet: inhomogeneous heat distribution on the wall and a narrow heating area. However, inhomogeneous heat transfers still occur. Therefore, a new jet control is required to improve the uniformity of heat transfer. Meanwhile, blooming jets are produced by appropriate combinations of axial and helical excitations at the nozzle exit. Using appropriately selected excitations, a jet can split into two separate jets (bifurcating jet) or spread into a shower of toroidal vortex rings. Blooming jets exhibit good performances of mixing and diffusion, suggesting possible applications in flow control. However, studies regarding the heat transfer performance of blooming jets are non-existent. In this study, we conducted direct numerical simulations of blooming jets impinging upon a wall and investigated their flow characteristics and heat transfer performances. As control parameters, the impingement distance (the distance from the nozzle to the wall) and frequency ratio (the axial excitation frequency to the helical frequency) are varied. The vortex structures and velocity magnitude reveals flow modulations due to blooming control. With the time-averaged local Nusselt number, the heat transfer performance of the blooming jets is evaluated quantitatively. Compared with uncontrolled jets, the uniformity of heat transfer of blooming jets is better, suggesting their potential application for leveling the heat transfer of impinging jets.https://www.jstage.jst.go.jp/article/jfst/15/2/15_2020jfst0010/_pdf/-char/endirect numerical simulation (dns)blooming jetflow controlimpinging jetheat transfer |
| spellingShingle | Kentaro ECHIGO Koichi TSUJIMOTO Toshihiko SHAKOUCHI Toshitake ANDO Flow and heat transfer characteristics of blooming jets impinging upon wall using DNS Journal of Fluid Science and Technology direct numerical simulation (dns) blooming jet flow control impinging jet heat transfer |
| title | Flow and heat transfer characteristics of blooming jets impinging upon wall using DNS |
| title_full | Flow and heat transfer characteristics of blooming jets impinging upon wall using DNS |
| title_fullStr | Flow and heat transfer characteristics of blooming jets impinging upon wall using DNS |
| title_full_unstemmed | Flow and heat transfer characteristics of blooming jets impinging upon wall using DNS |
| title_short | Flow and heat transfer characteristics of blooming jets impinging upon wall using DNS |
| title_sort | flow and heat transfer characteristics of blooming jets impinging upon wall using dns |
| topic | direct numerical simulation (dns) blooming jet flow control impinging jet heat transfer |
| url | https://www.jstage.jst.go.jp/article/jfst/15/2/15_2020jfst0010/_pdf/-char/en |
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