Strouhal number data for two staggered circular cylinders

Vortex shedding from two staggered circular cylinders of equal diameters was studied experimentally at Re = 3.2 x 10(4)-7.4 x 10(4). The centre-to-centre pitch ratio ranged from P/D = 1.125 to 4.0 and the incidence angle was varied in small increments from alpha = 0 degrees to 90 degrees. The behaviour of the Strouhal number data depended on whether the cylinders were closely, moderately, or widely spaced. For closely spaced staggered cylinders, P/D< 1.5, the flow pattern is similar to a single bluff body, and only a single Strouhal number is measured. For moderately spaced cylinders, 1.5 <= P/D <= 2.5, two distinct Strouhal numbers are measured when alpha > 30 degrees, but there is some scatter in the Strouhal data when alpha < 30 degrees. For widely spaced cylinders, P/D > 2.5, the Strouhal numbers are close to the single-cylinder value. (c) 2007 Elsevier Ltd. All rights reserved.