Flow Around a Rotatable Circular Cylinder-Plate Body at Subcritical Reynolds Numbers

摘要

The behavior of a stationary circular cylinder with an attached plate, under conditions where the entire cylinder-plate body rotates about the cylinder axis, has been investigated experimentally for Reynolds numbers between 8 x 10~3 and 6 X 10~4. To see the effect of the plate inclination on the pressure distributions and vortex shedding, the cylinder-plate body was rotated from 0 to 180 deg, unlike freely rotatable cases in previous studies. The plate was located at the center plane of the cylinder, upstream of the cylinder, at the beginning. The diameter of the cylinder and the width of the plate were both chosen to be 35 mm. Measurements of shedding frequency and pressures on the surface of the cylinder were obtained. The results indicate that the shedding frequency was nearly constant in the range of 50-120 deg and, by further increasing the angle from 120 to 160 deg, it strikingly increases and then again decreases at angles larger than 160 deg. The plate also causes important changes in pressures on the surface of the cylinder with increasing inclination angle. For different plate angles, five different types of pressure distributions have been observed. Characteristics of the vortex formation region and location of flow attachments, reattachments, and separations were observed by means of the flow visualizations. The drag coefficient of the cylinder has a maximum value at approximately θ = 75 deg, whereas it has a minimum value at θ = 15 deg. The lift coefficient has two maximums, at θ = 15 and 165 deg, depending on the plate position. The values of C_L at about θ = 45 and 160 deg are zero as in the case of the cylinder without a plate.