Unsteady lift force on a towed sphere

An experimental effort to characterize the broadband flow-induced lift forc es on a spherical body that is towed underwater is described. The body itse lf is the transducer which is comprised of a small geophone encased in a ne ar-neutrally-buoyant sphere, 7.62 cm in diameter. The research described in this paper quantifies the flow-induced unsteady lift force signal as a fun ction of the sphere diameter Reynolds number (7620 < Re < 34290) and the St rouhal number (1.5 < St < 30). It is found that the broadband flow-induced unsteady lift forces are proportional to the product of an area and the dyn amic pressure of the flow, as expected. These data are compared to similar data measured previously on a finite-length, right-circular cylinder in cro ss flow. This comparison indicates that the cylindrical body creates more u nsteady side force than does the spherical one, particularly at the lower e nd of the Strouhal number range. (C) 1998 Academic Press.