| The friction on a flat surface or a pipe is slowing the fluid in contact with the surface. The friction effect is the Fluid's increasing velocity, versus distance from surface.On the front of the surface, the fluid's flow is laminar, next a transition appears the flow at a critic distance ,and the flow become turbulent.
The area disturbed by fluid friction surface is the boundary layer beyond the thickness of the boundary layer, we consider that the fluid is no longer disturbed by the effects of friction surface.
The fluid within the boundary layer is disrupted and slowed relative to the fluid located outside the boundary layer.
details of the friction surface in mecaflux
In ducts there are a speed Maximum fluid at center line and speed decreasing to zero in intimate contact with the surface. To facilitate the calculation and manipulation of data, we are using a average speed .
The surface friction in the ducts are treated in friction pressure loss.
In hydrodynamics Naval the friction surface is called the viscous resistance (due to its dependence on parameter viscosity fluid). The frictional resistance (or viscous resistance) is only a part of the resistance drag in Aerodynamics or hydrodynamics .
The surface's roughness is a determining factor of the surface's friction force .
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