LES of the flow around two cylinders in tandem

The flow around an arrangement of two cylinders in tandem exhibits a remarkably complex behaviour that is of interest for many engineering problems, such as environmental flows or structural design. In the present paper, a Large Eddy Simulation using a staggered Cartesian grid has been performed for the flow around two cylinders in tandem of diameter D = 20 mm and height H = 50 mm submerged in an open channel with height h = 60 mm. The two axes have a streamwise spacing of 2D. The Reynolds number is 1500, based on the cylinder diameter and the free-stream velocity u(infinity). The results obtained show that no vortex shedding occurs in the gap between the two cylinders where the separated shear layers produced by the upstream cylinder reattach on the surface of the downstream one. The flow separates on the top of the first cylinder with the presence of two spiral nodes known as owl-face configuration. On top of the downstream cylinder, the flow is attached. A complex mean flow develops in the gap and also behind the second cylinder. Comparisons with PIV measurements reveal good general agreement, but there are differences concerning some details of the flow in the gap between the cylinders. (C) 2008 Elsevier Ltd. All rights reserved.