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Mechanism of wall turbulence in boundary layer flow. (English) Zbl 1173.76016
Summary: We use the energy gradient method to analyze the turbulence generation in transition boundary layer flows. It is found that the maximum of the energy gradient function occurs at the wall for the Blasius boundary layer. At this location for a sufficiently high Reynolds number, even a low level of free-stream disturbance can cause the transition to turbulence and sustain the flow to be turbulent. This is an excellent explanation of the physics of self-sustenance of wall turbulence. The mechanism of receptivity for boundary layer flows can also be understood from the energy gradient criterion. That is, the free-stream disturbance can propagate towards the wall by the “energy gradient” process to cause transition to turbulence, and the transition point in boundary layer can be moved towards the leading edge when the level of external disturbance increases.
MSC:
76F06Transition to turbulence
76D10Boundary-layer theory, separation and reattachment, etc. (incompressible viscous fluids)