The dynamics of flow around a cylinder at subcritical Reynolds numbers

Mean and fluctuating pressure and skin friction around a circular cylinder in cross-flow were studied in the subcritical Reynolds number range, 104–105. Results are presented for two cases, namely, with and without a splitter plate behind the cylinder. The splitter plate was used to suppress vortex shedding. The nonlinear dynamics of the flow around the cylinder was examined to characterize the process of laminar separation in terms of the number of degrees of freedom, and to determine whether the process is chaotic. For this purpose, the Grassberger–Procaccia correlation dimension and the largest Lyapunov exponent were estimated from the time series of the pressure data. The results indicate a correlation dimension of the order of 10–12 both in the presence and absence of the splitter plate. The largest Lyapunov exponent was found to be positive in both cases, suggesting that the process of laminar separation is chaotic. These results are new and are significant from the point of view of modeling and controlling the phenomenon of laminar separation in the future.