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The main parameter characterizing transition is the Reynolds number. Transition is often described as a process proceeding through a series of stages. Transitional flow can refer to transition in either direction, that is laminar–turbulent transitional or turbulent–laminar transitional flow.
The transition from laminar (left) to turbulent (right) flow of water from a tap occurs as the Reynolds number increases. A vortex street around a cylinder. This can occur around cylinders and spheres, for any fluid, cylinder size, and fluid speed provided that it has a Reynolds number between roughly 40 and 1000. [ 1 ]
As the Reynolds number increases, such as by increasing the flow rate of the fluid, the flow will transition from laminar to turbulent flow at a specific range of Reynolds numbers, the laminar–turbulent transition range depending on small disturbance levels in the fluid or imperfections in the flow system.
Conventionally, = 2.59 (Blasius boundary layer) is typical of laminar flows, while = 1.3 - 1.4 is typical of turbulent flows near the laminar-turbulent transition. [16] For turbulent flows near separation, 2.7. [17] The dividing line defining laminar-transitional and transitional-turbulent values is dependent on a number of factors so it is not ...
Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.
It is a function of Reynolds number of the flow. In case of laminar flow, this length is given by: , = [2] where is the Reynolds number and is the diameter of the pipe. But in the case of turbulent flow,
In aerodynamics for example, if one considers one particular airfoil, the Reynolds number value of the laminar–turbulent transition is one relevant dimensionless number of the problem. However, it is strictly related to the particular problem: for example, it is related to the airfoil being considered and also to the type of fluid in which it ...
Conceptually, the Reynolds number is the ratio between inertial forces and viscous forces. [6] Schlieren photograph showing the thermal convection plume rising from an ordinary candle in still air. The plume is initially laminar, but transition to turbulence occurs in the upper third of the image.