Abrasive flow finishing

Gary Derian gderian at cybergate.net
Fri Dec 19 13:09:21 GMT 1997


John,
    The Reynolds number is very important in determining fluid flow but is
is the ratio of inertia loss to viscous loss in a fluid stream.  Re =
(density x velocity x length) divided by viscosity and is dimensionless.
Adding bumps has no effect on Reynolds numbers.  Very low Re < 2,000 means
flow is always laminar.  Re > 5,000 means flow is always turbulent.  In the
range between 2,000 and 5,000 the flow is mixed and can be pushed into the
turbulent or laminar zone by careful design.

    Adding surface roughness puts more energy into the boundary layer and
may result in keeping it attached to the part.  The increase in drag caused
by the turbulent boundary layer is more than made up by the reduction in
drag caused by the streamlines remaining attached to the part.

Gary Derian <gderian at cybergate.net>


>>>>I was thinking about the "random bumps reduce drag" effect. Perhaps
big snip


John Buckbell wrote:
>The explanantion you are looking for is called Reynolds number.
>Reynolds number is a dimensionless parameter used to express the
>relationship between free-stream velocity and the size of the surface
>(length) in the flow.





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