New Shape Parameters for the Laminar, Transitional, and Turbulent Velocity Profiles

摘要

In this report a new method for describing the shape and thickness of 2-D wall bounded boundary layer velocity profiles is presented. The new method is based on calculating parameters using simple integrals of the velocity profile. It is shown that these new parameters can be used to describe both the inner and outer region of the turbulent boundary layer, as well as laminar and transitional velocity profiles. Applied to experimental laminar- turbulent profiles, it is shown that one of the new shape parameters foretells the beginning of the laminar turbulent transition on a flat plate at a much lower Reynolds number than the traditional H12 criteria. Furthermore, using another new parameter it is shown that the transition to fully turbulent flow may proceed as a discontinuous event.