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Index of Subjects Hi Dave, Here’s a back-of-the-envelope dimensional analysis that crudely explains why transported particle mass M is proportional to the sixth power of fluid velocity V: The force of the flowing water is reasonably proportional to the cross-sectional area of the particle, which is M^2/3. The force is also proportional to the square of the velocity (highschool physics conservation-of- momentum). So now you have force ~ (V2 ) (M^2/3) . To transport the particle you reasonably need the force to be of the order of magnitude of the mass, i.e. proportional to the mass. So M ~ (V2 )( M^2/3), or M ~ V6. I hope these exponent notations go through ok. Regards, Martial Thiebaux David & Alison Webster wrote: > Dear All, Dec 6, 2007 > I see in my old Forest Soils text that the size (weight) of particles > that can be transported by flowing water varies as the sixth power of > the velocity, i.e. if particles of size X can be transported at > velocity v then at 2v particles of size 64X can be transported. > > Can anyone take a stab at explaining the physics of a dX/dv this large ? > > Yt, Dave Webster, Kentville >
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