In fluid mechanics, a fluid's velocity is generally lowest:

In fluid mechanics, a fluid's velocity is generally lowest near the boundaries of the flow, which is associated with the effects of viscosity and the no-slip condition at the boundaries. In a pipe flow, for example, the fluid molecules in direct contact with the pipe walls adhere to the surface due to viscous forces and remain stationary. As you move away from the boundary and towards the center of the pipe, the velocity of the fluid increases until it reaches a maximum at the center.

This behavior is particularly evident in laminar flow conditions, where the fluid flows in parallel layers with minimal mixing. The velocity gradient near the boundaries results in slower-moving layers of fluid adjacent to the walls and faster-moving layers toward the center.

In turbulent flows, while there is a more complex interaction between fluid particles, the concept still holds that the velocity near boundaries, such as the walls of a pipe, is generally lower than that at the center. Thus, understanding how fluid velocity varies with distance from boundaries is crucial in various applications, including the design of pipelines, channels, and other hydraulic systems, where control over flow characteristics is essential.