Sphere Drag Measurements with the NAL 60cm MSBS

Abstract

Drag coefficients of a sphere were measured in support interference free by the NAL 60cm MSBS(Magnetic Suspension and Balance System) up to 3.5×10⁵ in Reynolds number. The magnetically supported sphere moved a little around tunnel center during tests. The displacement parallel to the flow is about 1/4 times as small as perpendicular one. The displacement perpendicular to the flow was distributed uniformly in direction at speed of 20m/s.The obtained drag coefficients show almost the same values as the other source data sets using a MSBS. In unsteady aerodynamic force on the sphere, rms values of the side force were about 4 times as large as parallel one at speed of 35m/s. Two kinds of averaged side force were observed at Reynolds numbers not less than 2.5×10⁵ while the same drag coefficient was measured. One increased rapidly with Reynolds number. The other keeps zero or very small magnitude as Reynolds number increases. Strouhal numbers were measured at three Reynolds numbers up to 2.8×10⁵ and they show good agreement with ones in other sources.