Study on force and wake features of side-by-side stepped circular cylindrical structures in uniform flow
Stepped circular cylinders are common structural shapes in engineering,whose force characteristics and wake patterns in flow fields are significantly influenced by the diameter ratio,presenting a highly complex mechanism.This complexity affects the accuracy of force values used in engineering design.In this paper,three-dimensional direct numerical simulations of flow past two side-by-side stepped circular cylinders were performed.A specific range of diameter ratio(D/d=1.33-2)was selected,and the lift and drag characteristics,the wake mode,and the vortex structures were analyzed.The wake modulation of the side-by-side stepped cylinders and its mechanism were investigated.The results show that the wake mode of the side-by-side stepped cylinders is influenced not only by the proximity interference of the wakes but also by the interactions between the wakes of the larger and smaller cylinders,consisting of the stepped cylinders.In the case of small diameter ratio(D/d=1.33),the wake shows a combined mode consisting of a stable deflection(DF)mode and an alternating deflection(FF)mode.The mean drag and vortex-shedding frequency of the cylinder with a narrower wake are higher while those of the cylinder with a wider wake are lower.However,in the cases of moderate to large diameter ratios(D/d=1.67 and 2),the wake shows the FF mode.The two stepped cylinders alternately show a higher drag and vortex-shedding frequency.Different vortex dislocations exist in the narrower and wider wakes,with the narrower wake being dominated by half-loop connections and direct connections while the wider wake being dominated by multi-connections.
stepped cylindersside-by-side configurationforce featurewake modediameter ratio
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