View source for Bagnold number

The '''Bagnold number''', named after [[Ralph Alger Bagnold]], used in [[granular material|granular]] flow calculations, is defined by

: <math>Ba=\frac{mD^2\gamma}{2\gamma_e\mu}</math>

where <big><math>m</math></big> is the mass, <big><math>D</math></big> is the grain diameter, <big><math>\gamma</math></big> is the [[surface tension]] and <big><math>\mu</math></big> is the [[interstitial fluid]] [[viscosity]].

Bagnold conducted experiments with 1 [[millimetre|mm]] wax spheres suspended in a glycerin-water-alcohol mixture were sheared in a coaxial cylinder rheometer. The rheometer was cleverly designed to measure both the shear and normal forces applied to the walls. He identified two distinct flow regimes: the macroviscous and the grain inertia. These regimes can be distinguished using a quantity that is now referred to as the Bagnold number.

==External links==
*[http://microgravity.grc.nasa.gov/fcarchive/fluids/papers/Hunt/Granular_Material_Flows.htm Granular Material Flows at N.A.S.A]

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[[Category:Granular materials]]

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