Experimental Investigation of the Effect of Reducing the Drag Coefficient on the Cylinder by Hot-Wire Anemometry

An experimental investigation on the cylinder having a length of 390 mm and a diameter of 20 mm at Reynolds number 18750 has been done. At the first, mean streamwise velocity profiles, then streamwise turbulence intensity profiles fixed and rotating circular cylinder (for spans 1000, 2000 and 3000 rpm) at three stations (x=30, 60,120 mm) behind the cylinder are discussed and compared. In order to measure the mean velocity and turbulence intensity, the hot-wire anemometry has been used. Also, the Strouhal number of fixed and rotating cylinders is compared. The results show that by increasing the rotational speed at a constant Reynolds number, if the direction of the cylinder is the agree of the fluid movement, the width of wake becomes smaller, and the Strouhal number of the wake associated with the Karman vortex increases. At the stations of 1 and 3 turbulences the rotating cylinder is more than the fixed cylinder, and the second station turbulences fixed cylinder is more than the rotating cylinder. It is found that by increasing the rotational speed, the parameters of drag coefficient and velocity defect reduce. By increasing the rotational speed, the drag coefficient reduced by about 10%.