Sting-free measurements of sphere drag in laminar flow

Abstract

An aerodynamic investigation was conducted to determine the laminar-flow drag coefficient of spheres of various sizes in a subsonic wind tunnel. The tests were conducted using the M.I.T.-N.A.S.A. prototype magnetic-balance system. By measuring the drag of different sized spheres without model support interference the tunnel wall effect can be deduced. The present results indicate that the classical wind tunnel correction does not completely account for the effects of model size and wall interference. That is, the corrected drag coefficient data for the different sphere sizes differ among themselves in the region of Reynolds number overlap.A comparison of the present sphere drag results with those of numerous other investigations including free-flight and ballistic-range data is given. The drag coefficients presented here are slightly lower than those of other workers for Reynolds numbers ranging from 20 000 to 150 000, but fall between the limits of experimental scatter for Reynolds numbers from 150 000 to 260 000.An analysis of the estimated error in the present data indicates the primary source to be measurement of the wind tunnel parameters rather than errors resulting from the balance system.

Magnus effect on a rotating sphere at high Reynolds numbers

“…One study that has been cited in almost all studies of the flow around non-rotating spheres is the one of Achenbach (1972) who was originally interested in the pneumatic transportation of spherical fuel elements in high-pressure tubes where high Reynolds numbers were expected. Contrary to the numerous studies on non-rotating spheres (Achenbach, 1972(Achenbach, , 1974a(Achenbach, , 1974bArakeri and Ram, 1984;Bakic, 2002;Calvert, 1972;Choi et al, 2006;Chomaz et al, 1993;Hoerner, 1935;Jang and Lee, 2008;Jeon et al, 2004;Kim and Durbin, 1988;Leder and Geropp, 1993;Maxworthy, 1969;Provansal et al, 2004;Quadflieg, 1975;Raithby and Eckert, 1968;Sakamoto and Haniu, 1990;Sawada et al, 2004;Suryanarayana et al, 1993;Suryanarayana and Meier, 1995;Suryanarayana and Prabhu, 2000;Taneda, 1978;Vlajinac and Covert, 1972;Willmarth and Enlow, 1969), the studies on rotating spheres focus on subcritical Reynolds numbers. Large Eddy Simulation (LES) of the flow over a rotating sphere was performed by Gora et al (2006) at Re D ¼1 Â 10 4 .…”

Teaching micro air vehicles how to fly as we teach babies how to walk

“…Laurenceau and Tournier (1957) first proposed the foundational concept of the MSBS for wind tunnel testing. Since the world's first practical use of the MSBS for wind tunnel testing by Vlajinac and Covert (1972), there have been several reports on the use of the MSBS for the experimental aerodynamic measurements (Dress, 1990;Higuchi et al, 2006Higuchi et al, , 2008Owen and Owen, 2007;Sawada and Suda, 2011;Vlajinac and Covert, 1972).…”

Vibrational characteristics of sphere model installed in wind tunnel test section

“…If a sphere is supported by a rear rod, the sphere wake can reattach to that rod, thereby distorting the downstream flow field [8]. Threedimensional models supported by a magnetic suspension system in a wind tunnel test section also have been trialed [9][10].…”