Buffeting forces induced by cross-flow through arrays of cylinders

Experimentally measured unsteady forces induced by a cross flow through a staggered array of smooth, rigid cylinders arranged in an equilateral pattern are reported. The test arrays were four rows deep, three arrays of pitch-to-diameter ratios 1.2, 1.5 and 1.71 being tested. The experiments spanned a Reynolds number, based on the freestream velocity and cylinder diameter, from 2 x 104 to 2 x 105. Measurements were made both in uniform flows and flows rendered turbulent by square mesh grids. Among the insights gained are an observation of a transition in the flow, reminiscent of an isolated cylinder, and the shift of that transition to lower Reynolds numbers by the turbulence in the flow. Systematic data are also presented of the variations in the force coefficients and Strouhal numbers as a function of the array parameters. (author)