FLOW PAST A BLUFF BODY WITH A WAVY STAGNATION FACE
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文摘
Numerical investigations have been performed to study the flow past square-section cylinders with a spanwise geometric deformation leading to a stagnation face with a sinusoidal waviness. The computations were performed using a spectral/hp element solver over a range of Reynolds numbers from 10 to 500. Starting from fully developed shedding past a straight cylinder at a Reynolds number of 100, a sufficiently high waviness is impulsively introduced resulting in the stabilization of the the near-wake to a time-independent state. The steady nature of the near-wake is associated with a reduction in total drag of about 16 % at a Reynolds number of 100 as compared with a straight, non-wavy cylinder. Further increases in the amplitude of the waviness lead to the emergence of hairpin vortices from the near-wake region, similar to the wake of a sphere at low Reynolds numbers. At higher Reynolds numbers, the drag reduction increases substantially, e.g. at a Reynolds number of 500 it is 34 % , principally due to the increase in drag of the nonwavy cylinder. Alternative methods based on three-dimensional forms of bleed are investigated to suppress the von-Kármán vortex street of a straight, non-wavy cylinder.