Resumen
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 k-? 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 x'-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 a = 15°. In addition, the standard deviation σx′" role="presentation">????'sx'
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of the time-averaged velocity U¯x′" role="presentation">???????????'U¯x'
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along the cylinder shows a trend of increasing at first and then decreasing, and that σy′" role="presentation">????'sy'
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also shows the same trend at a = 20°~45°; it fluctuates within a range of 0.05~0.2 at a = 0°~20°. Finally, two principal modes of vortex shedding are observed with a = 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 a = 15°; (ii) ?2 + 2? mode, four vortices shed off from the top and bottom sides of the cylinder at a > 15° in one vortex shedding period.