Drag on a group of cylinders

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1972

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Abstract

An experimental investigation of the drag on a group of circular cylinders, in a variety of spacings and immersed in a uniform flow, was conducted. The study was made to determine how the presence of the other cylinders affect the loading on a given cylinder. The drag was determined by means of strain-gage measurements. The Reynolds number range over which the measurements were made was 2.78x10[superscript 4] to 7.82x10[superscript 4]. The results are presented in the form of diagrams of drag coefficient versus spacing at a given orientation and Reynolds number. Drag coefficient data were corrected for blockage effects in the wind tunnel. It was found that strong interaction exists between the cylinders when the axis of the row of cylinders is parallel to the direction of the flow. This interaction becomes gradually smaller as the orientation angle, which is the angle formed between the axis of the cylinders and the flow direction increases. At ninety degrees, or when the axis of the row of cylinders is perpendicular to the direction of the flow, the interaction is only noticeable when the cylinders are spaced very closely (less than twice the diameter of the cylinders). The tests were conducted for spacing varying from 1/8 diameters up to 4 diameters between cylinders. Preliminary tests showed that the drag coefficients were almost constant for spacings larger than four diameters. The drag coefficients varied only slightly with changing Reynolds number in the range that this study involves. This is to be expected since the drag coefficient for a single cylinder is nearly constant for all Reynolds numbers in the given range.

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