角柱列を過ぎる流れの合流現象と乱流への遷移

Interactions between the wakes in a flow past a row of square bars are investigated by numerical simulations, the linear stability analysis and the bifurcation analysis. It is assumed that the row of square bars is placed across a uniform flow. Two-dimensional and incompressible flow field is also assumed. The flow is steady and symmetric along a streamwise centerline through the center of each square bar at low Reynolds numbers. However, it becomes unsteady and periodic in time at the Reynolds numbers larger than a critical value, and then the wakes behind the square bars become oscillatory. It is found by numerical simulations that vortices are shed synchronously from every couple of adjacent square bars in the same phase or in the anti-phase depending upon the distance between the bars. The synchronous shedding of vortices is clarified to occur due to an instability of the steady symmetric flow by the linear stability analysis. The bifurcation diagram of the flow is obtained and the critical Reynolds number of the instability is evaluated numerically.