Gap effect on transversal force acting on infinite array of cylinders at low KC and β

This paper deals with the numerical investigation of an oscillating, 3-dimensional flow over an infinite array of circular cylinders. Two different flow regimes, asymmetric and 3-D, have been investigated. The gap between 2 neighboring cylinders has been changed in a very wide range. A nonmonotonic behavior has been observed in the time evolution of the transversal force and consequently on the root mean square (r.m.s.) variation of this force with the gap. For large to moderate values of the gap, its reduction enhances the 3-D modulation of the transversal force; a further reduction of the gap in the range of small values tends to suppress the axial instability that leads to 3-D motion in the flow field.