PERIODIC-FLOW IN THE NEAR WAKE OF STRAIGHT CIRCULAR-CYLINDERS

The formation of periodic waves in the near wake of straight circular cylinders with arbitrary aspect ratios in crosswise flows at low Reynolds numbers (Re) is analyzed. Using a semiempirical model it is shown that raising the Reynolds number beyond a critical value of about Re(1) = 22 yields a supercritical Hopf bifurcation preceding the known onset of the von Karman vortex flow at about Re(2) = 46.7. In agreement with experimental trends a stable periodic, secondary transversal motion arises in the previously steady crosswise flow.