Laminar Flow

Facts about laminar flow


By: Anthony Orozco, Journalist

Laminar flow, also called streamline flow, is when a type of fluid (gas or liquid) flow travels smoothly or in regular paths. This is different from turbulent flow, which is where the fluid undergoes irregular fluctuations and mixing. In laminar flow, the velocity, pressure, and other flow properties at each point in the fluid are the same, causing an effect that makes the flow seem “still.” Laminar flow over a horizontal surface can be seen as thin layers, or laminae, all traveling parallel to each other. The fluid in contact with the horizontal surface is stationary, but all the other layers slide over one another. Laminar flow in a straight pipe may be seen as the relative motion of a set of concentric cylinders of fluid, the outside one fixed at the pipe wall, and the others moving at increasing speeds as the center of the pipe is approached. Smoke rising in a straight path from a cigarette is undergoing laminar flow. After rising a little, the smoke usually changes to turbulent flow as it swirls from its regular path. Laminar flow is common only when the flow channel is relatively small, the fluid is moving slowly, and its viscosity, or thickness, is relatively high. Oil flow through a thin tube or blood flow through capillaries is an example of laminar flow. Most other kinds of fluid flow are turbulent unless near solid boundaries, where the flow is often laminar, especially in a thin layer adjacent to the surface.

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