TRANSITION WAVES AND NONLINEAR-INTERACTIONS IN THE NEAR WAKE OF A CIRCULAR-CYLINDER

Transition waves and interactions between two kinds of instability-vor tex shedding and transition wave in the near wake of a circular cylind er in the Reynolds number range 3 000-10 000 are studied by a domain d ecomposition hybrid numerical method. Based on high resolution power s pectral analyses for velocity new results on the Reynolds-number depen dence of the transition wave frequency, i.e. f(t)/f(s) similar to Re-0 .87 are obtained. The new predictions are in good agreement with the e xperimental results of Wei and Smith but different from Braza's predic tion and some early experimental results f(t)/f(s) similar to Re-0.5 g iven by Bloor et nl. The multi-interactions between two kinds of vorte x are clearly visualized numerically. The strong nonlinear interaction s between the two independent frequencies (f(t), f(s)) leading to spec tra broadening to form the coupling mf(s) +/- nf(t) are predicted and analyzed numerically, and the characteristics of the transition are de scribed. Longitudinal variations of the transition wave and its coupli ng are reported. Detailed mechanism of the flow transition in the near wake before occurrence of the three-dimensional evolution is provided .