Experimental investigation of rotating cylinders in flow

Abstract

Rotating cylinders with different diameters placed in uniform flow were investigated experimentally. The aspect ratios, $${\text{AS}}$$ (ratio of the length and the diameter) of cylinders, with the same length $$L=0.59\;{\text{m}}$$ were 1.85, 2.21, 2.73 and 5.78 with respective diameters of 0.319, 0.267, 0.216 and 0.102 m. The non-dimensional rotation rate, $$\alpha$$ , was the ratio of the rotating surface speed and the flow speed, which varied from 0 to 8 for the 0.319 m diameter cylinder. Hydrodynamics of the cylinders were analyzed based on two different conditions: cylinders in flow condition and rotating cylinders in flow condition. For the cylinders in flow, the influence of the aspect ratio and Reynolds number on the hydrodynamics coefficient and Strouhal number was discussed, the critical transition area was found at $$1.0 \times {10^5} \leqslant Re \leqslant 1.59 \times {10^5}$$ . For the cylinders rotating in flow, initial area, increasing area and equivalent area were defined to describe the variation of mean of hydrodynamics as the increase of rotation rates. The range of these areas was decided by the rotation rate and aspect ratio of the cylinders. Different from the mean hydrodynamics, for the Strouhal number (vortex shedding) and Root mean square of lift for the rotating cylinders, vortex shedding area, weak vortex shedding area and wake fluctuation area were defined to explain them and the range of these areas was only determined by rotation rate.