Laminar flow ( lat. Lāmina - “plate”) is a flow in which a liquid or gas moves in layers without mixing and pulsation (that is, without random rapid changes in speed and pressure).
| Flow liquids and gas | |
| Creeping current | |
| Laminar flow | |
| Potential flow | |
| Flow gap | |
| Vortex | |
| Instability | |
| Turbulence | |
| Convection | |
| Shock wave | |
| Supersonic flow | |
Until 1917, the term streamed in Russian science was used. .
Only in the laminar mode, it is possible to obtain exact solutions of the equation of motion of a fluid ( Navier – Stokes equations ), for example, the Poiseuille flow .
Transition to Turbulence
Laminar flow is possible only up to a certain critical value of the Reynolds number , after which it becomes turbulent . The critical value of the Reynolds number depends on the specific type of flow (flow in a circular tube, flow around a ball, etc.). For example, for flow in a round tube .
In some cases, to obtain a threshold Reynolds number, it suffices to perform a linear stability analysis — a theoretical analysis of stability under the influence of infinitely small perturbations. For example, thresholds for flow between parallel planes and the Couette-Taylor flow between rotating cylinders are obtained. However, in some cases, linear analysis is not enough: for a flow in a circular pipe, it leads to absolute stability, which is refuted by experiments.
In hydraulics , if the pipe is not circular, then calculated by hydraulic diameter
Where - the cross-sectional area of the pipe, - full wetted perimeter .
See also
- Froude number
- Reynolds number