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RISS 인기검색어
- 검색키워드
- 저자 : Raheela Manzoor (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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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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Drag reduction on a square cylinder using multiple detached control cylinders
Shams-Ul-Islam,Raheela Manzoor,Umar Khan,Ghazala Nazeer,Sehrish Hassan 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.5
A two-dimensional numerical simulation for flow over a main cylinder with detached controlling cylinders placed at differentposition is performed through Lattice Boltzmann Method (LBM) to reduce fluid forces. For this study the Reynolds number (Re) isfixed at 160, while gap ratio between these cylinders are taken in the range from 0.5 to 8. The results yield in terms of vorticity, timeseriesanalysis of drag and lift coefficients, power spectra of lift coefficients and force statistics. Depending on gap spacing, flow isclassified into four different patterns, called as (i) single blender body, (ii) shear layer reattachment, (iii) fully developed flow and (iv)vortex suppression fully developed flow patterns. In comparison of all three configurations, it is examined that the maximum value ofCdmean and Strouhal number occurs for downstream configuration. Whereas, upstream and dual configuration play a vital role toreduce forces and to suppress vortex shedding. The maximum reduction found in mean drag coefficient for downstream, upstreamand for dual configuration is 8.3%, 51% and 50.8%, respectively. Whereas, the reduction in Clrms values for all three configurationsis 84.4%, 58.2% and 86.4% , respectively.
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Shams Ul Islam,Raheela Manzoor,Zhou Chao Ying,Mohammad Mehdi Rashdi,A. Khan 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2
A two-dimensional numerical study is carried out to analyze the drag reduction and vortex shedding suppression behind a square cylinder in presence of splitter plate arranged in upstream, downstream and both upstream and downstream location at low Reynolds number (Re = 160). Computations are performed using a Single relaxation time lattice Boltzmann method (SRT-LBM). Firstly, the code is validated for flow past a single square cylinder. The obtained results are compared to those available in literature and found to be in good agreement. Numerical simulations are performed in the ranges of 1 ≤ L ≤ 4 and 0 ≤ g ≤ 7, where L and g are the length of splitter plate and gap spacing between the splitter plate and main square cylinder, respectively. The effect of these parameters on the vortex shedding frequency, time-trace analysis of drag and lift coefficients, power spectra analysis of lift coefficient, vorticity contours visualization and force exerted on the cylinder are quantified together with the observed flow patterns around the main cylinder and within the gap spacings. The observed results are also compared with a single square cylinder without splitter plate. We found that at some combinations of L and g, the mean drag coefficient and Strouhal number reach either its maximum or minimum value. It is found that the drag is reduced up to 62.2 %, 13.3 % and 70.2 % for upstream, downstream and dual splitter plates, respectively as compared to a single square cylinder (without splitter plate). In addition, in this paper we also discussed the applications of SRT-LBM for suppression of vortex shedding and reduction of the drag coefficients.
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