FLOW INTERACTION BEHIND 2 CIRCULAR-CYLINDERS OF EQUAL DIAMETER - A NUMERICAL STUDY

Incompressible flows past two circular cylinders placed side by side i n a uniform stream were investigated numerically by the discrete vorte x model. The calculations were carried out at T/d = 1.25, 1.75, 3.0 an d 3.5, where T is the transverse distance between cylinder centers and d the cylinder diameter. The flow development was initiated by imposi ng a perturbation of short duration on the separated shear layers from the cylinders and four modes of perturbation were tried. For the mode 2 perturbation of T/d = 1.25, 3.0 and 3.5, the single vortex street, out-of-phase and in-phase vortex shedding modes were observed, respect ively, agreeing with the well-known experimental results. At the bista ble flow of T/d = 1.75 an asymmetric mode of vortex shedding was obser ved and the possible effects on flow parameters such as lift and drag were discussed.