Experimental Investigation of Perforated Plate Turbulent Flow Past a Solid Sphere

As the first stage of a comprehensive investigation of turbulence effect on the aerodynamics of sphere, the effect of freestream turbulence on the wake generated behind a sphere is investigated in this study. A 10 cm (4 in) diameter plastic sphere was placed in a wind tunnel of cross section 75 cm by 75 cm. The freestream turbulence was generated by fixing a perforated plate to the entrance of the test section. The wake was characterized using a normal constant-temperature hotwire at 30D, 40D and 50D (11.25d, 15d & 18.75d respectively) downstream of the sphere (where D = 3.75 cm is the diameter of the perforated plate hole, and d is the diameter of the sphere). The Reynolds number of the flow, based on the mean velocity and the diameter of the sphere, was 6.6 × 10⁴. Based on the instantaneous velocity measurement, Kolmogorov length scale, integral length scale and relative turbulence intensity in the wake were deduced.