Stability of the flow past a row of square bars

The stability of the flow past a row of square bars, which is placed across a uniform flow, is investigated numerically. Two-dimensional and incompressible flow field is assumed. It is found that each jet which flows between the square bars is independent of each other when the pitch-to-diameter ratio of the row is large. However the confluence of several jets occurs when the pitch-to-diameter ratio is small. It is found that the confluence of couples or triplets of jets is a consequence of a pitchfork bifurcation and the critical Reynolds numbers for the pitchfork bifurcations are evaluated for each value of the pitch-to-diameter ratio. An experiment to visualize the flow field is also made and the confluence of jets is confirmed.