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RISS 인기검색어
- 검색키워드
- 저자 : Waqas Sarwar Abbasi (검색결과 3 건)
- 무료
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Waqas Sarwar Abbasi,Shams-Ul-Islam,Suvash C. Saha,Yuan Tong Gu,Zhou Chao Ying 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.2
In this paper two-dimensional (2-D) numerical investigation of flow past four square cylinders in an in-line square configuration areperformed using the lattice Boltzmann method. The gap spacing g = s/d is set at 1, 3 and 6 and Reynolds number ranging from Re = 60 to175. We observed four distinct wake patterns: (i) a steady wake pattern (Re = 60 and g = 1); (ii) a stable shielding wake pattern (80 ≤ Re≤ 175 and g = 1); (iii) a wiggling shielding wake pattern (60 ≤ Re ≤ 175 and g = 3) and (iv) a vortex shedding wake pattern (60 ≤ Re ≤175 and g = 6). At g = 1, the Reynolds number is observed to have a strong effect on the wake patterns. It is also found that at g = 1, thesecondary cylinder interaction frequency significantly contributes for drag and lift coefficients signal. It is found that the primary vortexshedding frequency dominates the flow and the role of secondary cylinder interaction frequency almost vanish at g = 6. It is observed thatthe jet between the gaps strongly influenced the wake interaction for different gap spacing and Reynolds number combination. To fullyunderstand the wake transformations the details vorticity contour visualization, power spectra of lift coefficient signal and time signalanalysis of drag and lift coefficients also presented in this paper.
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Shams-Ul-Islam,Hamid Rahman,Waqas Sarwar Abbasi,Uzma Noreen,Aftab Khan 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.12
A numerical study for flow past a square cylinder in a two-dimensional channel with a detached flat plate is investigated in this paper. A flat plate is detached downstream in order to control the flow around and behind the square cylinder. Fluid forces acting on the squarecylinder, wake structure mechanism and vortex shedding frequency are presented systematically for different Reynolds numbers andspacing ratios. Effects of Reynolds numbers upon physical parameters are also studied. Variation of Reynolds number is from 75 to 200,based on the incoming flow velocity and width of cylinder. The lattice Boltzmann method is used for this numerical investigation. In thisstudy, we choose three different spacing ratios namely closely, moderately and widely. Numerical studies show that some physical parameterssignificantly reduced by the detached flat plate for closely spacing ratio. The results which we obtained in this investigation areauthentic in the sense that some other experimental observations by different authors can be deduced from our results.
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Variation of wake patterns and force coefficients of the flow past square bodies aligned inline
Raheela Manzoor,Shams-Ul-Islam,Waqas Sarwar Abbasi,Sajida Parveen 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.4
In this numerical study, the variation of wake patterns and force coefficients of the flow past four square bodies aligned inline are investigated. A two-dimensional numerical code is developed using the Lattice Boltzmann method (LBM) for this study. The code is first validated for the flow past a single and two tandem square cylinders. The results are compared to those available in literature and found to be in good agreement. After validation the calculations are further performed to investigate the effect of gap spacing (g) for the flow past four inline square cylinders at two different Reynolds numbers (Re) 100 and 200. The gap spacing is chosen in the range 0.25 ≤ g ≤ 7. Six different flow patterns: Single slender body, alternate reattachment, quasi steady reattachment, intermittent shedding, chaotic flow and periodic flow are found in this study with successive increment in spacing. It is found that some flow patterns existing at Re = 100 do not exist at Re = 200. The generated vortices at Re = 200 are much stronger as compared to those at Re = 100. The spacing value g = 3 is found to be critical at Re = 100 while at Re = 200 the spacing value g = 2 is critical due to abrupt changes in flow characteristics. At some spacing values the downstream cylinders have higher values of average drag coefficients as compared to upstream ones. In general the upstream cylinder (c1) have higher drag forces at Re = 200 than at Re = 100. The root mean square values of lift coefficient are found to be greater than the corresponding root mean square values of drag coefficient.
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