Inherent mechanism of breakdown in laminar-turbulent transition*

The conventional idea of Laminar-turbulent transition is that the transition starts from the amplification of disturbances, and when the disturbances become larger, higher harmonics will be generated due to non-linear effect, making the flow more and more complicated, and finally becomes turbulent. Though the scenario seems is clear, yet there is a missing link, that is, what happens in the breakdown process. Here we show by analyzing the results from direct numerical simulations that the change of stability characteristics of the mean flow profile plays a key role in the breakdown process.