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The path from receptivity to laminar-turbulent transition as illustrated by Morkovin, 1994 [2] A boundary layer can transition to turbulence through a number of paths. Which path is realized physically depends on the initial conditions such as initial disturbance amplitude and surface roughness.
A bypass transition is a laminar–turbulent transition in a fluid flow over a surface. It occurs when a laminar boundary layer transitions to a turbulent one through some secondary instability mode, bypassing some of the pre-transitional events that typically occur in a natural laminar–turbulent transition. [a]
This has the potential to freeze laminar slip (laminar interlocking) in these spots, transferring the resistance to the boundary: this breaking at the boundary could rip out pieces of T-S long-crested waves which would tumble head-over-heels downstream in the boundary layer as the vortices of turbulent spots.
Usually, there is a transition from laminar to turbulent as the plume moves away from its source. This phenomenon can be clearly seen in the rising column of smoke from a cigarette. When high accuracy is required, computational fluid dynamics (CFD) can be employed to simulate plumes, but the results can be sensitive to the turbulence model chosen.
Reynolds Experiment (1883). Osborne Reynolds standing beside his apparatus. In 1883, scientist Osborne Reynolds conducted a fluid dynamics experiment involving water and dye, where he adjusted the velocities of the fluids and observed the transition from laminar to turbulent flow, characterized by the formation of eddies and vortices. [5]
Laminar flow tends to dominate in the fast-moving center of the pipe while slower-moving turbulent flow dominates near the wall. As the Reynolds number increases, the continuous turbulent-flow moves closer to the inlet and the intermittency in between increases, until the flow becomes fully turbulent at Re D > 2900. [ 13 ]
With respect to laminar and turbulent flow regimes: laminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion; turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce chaotic eddies, vortices and other flow instabilities.
Transition modeling is the use of a model to predict the change from laminar and turbulent flows in fluids and their respective effects on the overall solution. The complexity and lack of understanding of the underlining physics of the problems makes simulating the interaction between laminar and turbulent flow to be difficult and very case specific.