In the present paper, the aerodynamic characteristics of a single vertical cylinder as well as two vertical circular vertical cylinders aligned side-by-side (whose centerline is perpendicular to the flow), located in the incompressible flow field, are numerically investigated. The flow simulations were carried out using unsteady 2D (infinitely long cylinders) and 3D numerical model (finite cylinders) and the finite volume CFD code FLUENT V 6.2.16. The standard k- turbulence model was used to account for turbulence effects in the flow field but with a special treatment at walls to account for flow separation. In the two dimensional flow fields, two cases were studied: a single cylinder model, where the effect of Reynolds number on the flow characteristics was investigated, and two side-by-side cylinders, where the effect of gap ratio (center-to-center distance divided by the cylinder diameter) is studied. The three dimensional case comprises two models. One model is a single finite cylinder, where the effects of turbulent boundary layer with different velocity gradient (/H= 0, 0.5, 0.8 and 1.3) and the cylinder aspect ratio (H/D=0.5, 1 and 2) are investigated. The other 3-D model consists of two finite cylinders (H/D=0.5) in side-by-side arrangement, with different gap ratios (L/D=1.25, 1.5, 1.75 and 2).