Numerical Investigation of Vortex Shedding from a 5:1 Rectangular Cylinder at Different Angles of Attack
Although flow around a 5:1 rectangular cylinder at small angles of attack (AoA) has been extensively studied, when the AoA becomes larger, the research is rare. Therefore, this study performs Unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) using the <i>k-ω</i> SST turbulence...
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MDPI AG
2022-12-01
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| Series: | Journal of Marine Science and Engineering |
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| Online Access: | https://www.mdpi.com/2077-1312/10/12/1913 |
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| author | Jian Wu Yakun Liu Di Zhang Ze Cao Zijun Guo |
| author_facet | Jian Wu Yakun Liu Di Zhang Ze Cao Zijun Guo |
| author_sort | Jian Wu |
| collection | DOAJ |
| description | Although flow around a 5:1 rectangular cylinder at small angles of attack (AoA) has been extensively studied, when the AoA becomes larger, the research is rare. Therefore, this study performs Unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) using the <i>k-ω</i> SST turbulence model for unsteady flow around a two-dimensional 5:1 rectangular cylinder at different AoAs up to 45°. A strong dependence of the flow characteristics on AoA is observed through the analysis of the time-averaged lift coefficient, drag coefficient, and Strouhal number. The peak of lift and drag coefficient is observed to be correlated, respectively, to the leading- and trailing-edge vortex based on the analysis of the flow. The <i>x′</i>-directional length of the main recirculation bubble on the top side and the distance from the bubble center to the leading edge of the cylinder both reach the maximum when α = 15°. In addition, the standard deviation <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>x</mi><mo>′</mo></mrow></msub></mrow></semantics></math></inline-formula> of the time-averaged velocity <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mover accent="true"><mi>U</mi><mo>¯</mo></mover><mrow><mi>x</mi><mo>′</mo></mrow></msub></mrow></semantics></math></inline-formula> along the cylinder shows a trend of increasing at first and then decreasing, and that <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>y</mi><mo>′</mo></mrow></msub></mrow></semantics></math></inline-formula> also shows the same trend at α = 20°~45°; it fluctuates within a range of 0.05~0.2 at α = 0°~20°. Finally, two principal modes of vortex shedding are observed with α = 15° being their turning point, (i) “1 + 1” mode: in one vortex shedding period, two major vortices shed off from the top and bottom sides of the cylinder at α ≤ 15°; (ii) “2 + 2” mode, four vortices shed off from the top and bottom sides of the cylinder at α > 15° in one vortex shedding period. |
| first_indexed | 2024-03-09T16:14:16Z |
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| language | English |
| last_indexed | 2024-03-09T16:14:16Z |
| publishDate | 2022-12-01 |
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| spelling | doaj.art-cac1d1f1bd6c4800a69894401cd851762023-11-24T15:56:29ZengMDPI AGJournal of Marine Science and Engineering2077-13122022-12-011012191310.3390/jmse10121913Numerical Investigation of Vortex Shedding from a 5:1 Rectangular Cylinder at Different Angles of AttackJian Wu0Yakun Liu1Di Zhang2Ze Cao3Zijun Guo4School of Hydraulic Engineering, Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, ChinaSchool of Hydraulic Engineering, Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, ChinaSchool of Hydraulic Engineering, Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, ChinaSchool of Hydraulic Engineering, Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, ChinaChina Water & Power Press, Beijing 100038, ChinaAlthough flow around a 5:1 rectangular cylinder at small angles of attack (AoA) has been extensively studied, when the AoA becomes larger, the research is rare. Therefore, this study performs Unsteady Reynolds-Averaged Navier-Stokes simulations (URANS) using the <i>k-ω</i> SST turbulence model for unsteady flow around a two-dimensional 5:1 rectangular cylinder at different AoAs up to 45°. A strong dependence of the flow characteristics on AoA is observed through the analysis of the time-averaged lift coefficient, drag coefficient, and Strouhal number. The peak of lift and drag coefficient is observed to be correlated, respectively, to the leading- and trailing-edge vortex based on the analysis of the flow. The <i>x′</i>-directional length of the main recirculation bubble on the top side and the distance from the bubble center to the leading edge of the cylinder both reach the maximum when α = 15°. In addition, the standard deviation <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>x</mi><mo>′</mo></mrow></msub></mrow></semantics></math></inline-formula> of the time-averaged velocity <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mover accent="true"><mi>U</mi><mo>¯</mo></mover><mrow><mi>x</mi><mo>′</mo></mrow></msub></mrow></semantics></math></inline-formula> along the cylinder shows a trend of increasing at first and then decreasing, and that <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>σ</mi><mrow><mi>y</mi><mo>′</mo></mrow></msub></mrow></semantics></math></inline-formula> also shows the same trend at α = 20°~45°; it fluctuates within a range of 0.05~0.2 at α = 0°~20°. Finally, two principal modes of vortex shedding are observed with α = 15° being their turning point, (i) “1 + 1” mode: in one vortex shedding period, two major vortices shed off from the top and bottom sides of the cylinder at α ≤ 15°; (ii) “2 + 2” mode, four vortices shed off from the top and bottom sides of the cylinder at α > 15° in one vortex shedding period.https://www.mdpi.com/2077-1312/10/12/1913rectangular cylinderBARC benchmarkangle of attackflow structuresvortex coupling mode |
| spellingShingle | Jian Wu Yakun Liu Di Zhang Ze Cao Zijun Guo Numerical Investigation of Vortex Shedding from a 5:1 Rectangular Cylinder at Different Angles of Attack Journal of Marine Science and Engineering rectangular cylinder BARC benchmark angle of attack flow structures vortex coupling mode |
| title | Numerical Investigation of Vortex Shedding from a 5:1 Rectangular Cylinder at Different Angles of Attack |
| title_full | Numerical Investigation of Vortex Shedding from a 5:1 Rectangular Cylinder at Different Angles of Attack |
| title_fullStr | Numerical Investigation of Vortex Shedding from a 5:1 Rectangular Cylinder at Different Angles of Attack |
| title_full_unstemmed | Numerical Investigation of Vortex Shedding from a 5:1 Rectangular Cylinder at Different Angles of Attack |
| title_short | Numerical Investigation of Vortex Shedding from a 5:1 Rectangular Cylinder at Different Angles of Attack |
| title_sort | numerical investigation of vortex shedding from a 5 1 rectangular cylinder at different angles of attack |
| topic | rectangular cylinder BARC benchmark angle of attack flow structures vortex coupling mode |
| url | https://www.mdpi.com/2077-1312/10/12/1913 |
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