Aerodynamic effects of the early three-dimensional instabilities in the flow over one and two circular cylinders in tandem predicted by the lattice Boltzmann method

The aerodynamic effects due to the development of 3D flow structures in the flow over one and two cylinders in tandem were studied numerically, using the lattice Boltzmann method. 2D and 3D simulations were conducted for one and two cylinders with cylinder spacings in the range of 1.5d-8d, at Reynolds numbers in the range of 160-220. The presence of Mode A instabilities were confirmed for cylinder spacings larger than 4d, as well as the T3 modes at a cylinder spacing of 3d. It was found that the 3D structures resulting from the Mode A instabilities have significant effects on the Strouhal number and forces acting on the cylinders. However, for the Reynolds numbers studied, the forces acting on the upstream cylinder were less affected by the 3D instabilities than in the single cylinder case. It was also found that the T3 mode has a different effect on the force coefficients than the Mode A instabilities. (C) 2013 Elsevier Ltd. All rights reserved.