Bagnold number
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The Bagnold number, named after Ralph Alger Bagnold, used in granular flow calculations, is defined by
- <math>Ba=\frac{mD^2\gamma}{2\gamma_e\mu}</math>
where <math>m</math> is the mass, <math>D</math> is the grain diameter, <math>\gamma</math> is the surface tension and <math>\mu</math> is the interstitial fluid viscosity.
Bagnold conducted experiments with 1 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.
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Dimensionless numbers in fluid dynamics |
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| Archimedes • Bagnold • Biot • Bond • Brinkman • Capillary • Damköhler • Dean • Deborah • Eckert • Ekman • Eötvös • Euler • Froude • Galilei • Grashof • Hagen • Knudsen • Laplace • Lewis • Mach • Magnetic Reynolds • Marangoni • Morton • Nusselt • Ohnesorge • Péclet • Prandtl • Rayleigh • Reynolds • Richardson • Roshko • Rossby• Ruark • Schmidt • Sherwood • Stanton • Stokes • Strouhal • Suratman • Taylor • Weber • Weissenberg • Womersley |
