Numerical simulation of turbulent wake flows behind two side-by-side cylinders

The formation and the convection of vortices behind two side-by-side cylinders are investigated using the large-eddy simulation (LES) model. Solution to the three-dimensional Navier-Stokes governing equations is obtained using a finite volume method with an unstructured mesh arrangement with hexahedral elements. The focus of the present investigation is to predict the wake dynamics at Reynolds numbers Re = 750 at two different cylinder spacings: large ratio T/d = 3 and intermediate ratio T/d = 1.7. The LES results revealed that for T/d = 3, the formation of symmetrical wakes behind the cylinders was observed. Two distinct vortex streets propagated downstream. However, for T/d = 1.7, owing to the close proximity of the two cylinders, the gap flow between the cylinders was deflected, forming one narrow and one wide wake behind the cylinders. It was also succinctly revealed that the gap flow deflection has a tendency to "flip", changing over from one side to another by being deflected upwards at a specific instance and downwards at later time. Qualitatively, the phenomenological predictions are in accordance with experimental observations. (C) 2003 Elsevier Ltd. All rights reserved.