| Popis: |
The development of streamwise‐oriented, symmetric, two‐dimensional vortices in curved channels of large aspect ratios is studied near the threshold of the first centrifugal instability. The nonlinear equations of motion governing the two‐dimensional, stationary flows are solved numerically over a range of parameter values. The dynamical parameter is the normalized streamwise pressure gradient defined as e=[(∂p/∂x)−(∂p/∂x)c]/(∂p/∂x)c, where (∂p/∂x)c is the critical value for the infinite geometry. The development of interior cells and the selection of the wavelength as e is gradually increased through zero is quite different from that observed in Taylor vortex flow. For pressure gradients of 0.5% and 1.0% (e=0.005, 0.01) above critical, the interior cells begin to grow spontaneously and are strongest in the middle of the channel. Unlike the interior cells in Taylor vortex flow, they are only weakly coupled to the end cells. The end cells (or Ekman vortices) are also found to be anomalously long.As e is inc... |
