Indian Journal of Science and Technology
Year: 2019, Volume: 12, Issue: 32, Pages: 1-13
S. Ul. Islam1*, R. Manzoor2, M. Zahid3, S. Kulsoom2 and U. Kausar2
1Department of Mathematics, COMSATS University of Information Technology, Islamabad–44000, Pakistan
2Department of Mathematics, SBK Women’s University, Quetta, Balochistan, Pakistan; [email protected]
3School of Mathematics and Statistics, Zhengzhou University, Henan–450001, China.
*Author for correspondence
S. Ul. Islam
Department of Mathematics, COMSATS University of Information Technology, Islamabad–44000, Pakistan.
Objectives: To examine the effect of unequal gap spacing for flow past over three rectangular rods a fixed Re (Reynolds number) and Aspect Ratio (AR). Methodology: A two dimensional (2-D) numerical study of flow over three rectangular rods is conducted by using Single Relaxation Time Lattice Boltzmann Method (SRT-LBM). The gap spacing (g) between the rods is varied from 0.5 to 7 with fixed Reynolds number i.e., Re = 150 (Re = .U∞d/ υ., where U∞ is uniform velocity, d is size of an object and υ is the kinematic viscosity) and aspect ratio AR = 0.25 (where, AR = l/w, l is the length and w is the width of the rods). Different flow structures, power spectra analysis of lift coefficients and force statistics are studied for this analysis at small, moderate and large gap spacing. Findings: The present study revealed that the gap spacing between the rods has a great impact on the flow behaviour. Therefore, different flow patterns are observed and some of them are outlined as, i). Shear layer reattachment (SLR), ii). Semi developed single bluff body (SDSBB), iii). Fully developed vortex shedding (FDVS), iv). Semi developed irregular vortex shedding, v) Fully generated two row single bluff body, vi). Semi developed irregular single bluff body (SDISBB) and vii). Critical flow (CF) patterns. The critical flow behaviour is observed at the gap spacing (g1 , g2 ) = (5, 2.5), (here, g1 is the gap between upstream rods to middle one and g2 is the gap between middle rods to downstream rectangular rod). In force statistics analysis, the values of Cdmean and Strouhal number are computed at different spacing ratios. The value of mean drags coefficients for all three rodsat g1 = 3 is approximately same, but at g1 = 1 and 5, the maximum value of Cdmean is observed for C2 as compared to C1 and C3, that is 6.91. Furthermore, Strouhal number values are much less than the single rod (SR) value for all three chosen small, moderate and large gap spacing values. The maximum value of St is examined at (g1, g2) = (1, 1) i.e 0.19.
Keywords: Drag Coefficient; Rectangular Rods, Single Relaxation Time Lattice Boltzmann Method, Vortex Shedding Suppression
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