Leighton number

In fluid mechanics, the Leighton number is the ratio of lubrication forces (η_sγ) to friction forces (σ), where η_s is the interstitial fluid viscosity, γ is the shear rate, σ is the total sheer stress. It is commonly denoted by Le and defines a critical shear rate (γ_c) where no steady flow without localization exist1. The Leighton number also is defined by Le = μγa/εσ_n, where εa is the mean distance between the surfaces of two close particles2. The transition between frictional and lubricated flow regimes is characterized by a viscosity bifurcation that is governed by the Leighton number.

It is named after David T. Leighton, currently a professor at the University of Notre Dame in the Department of Chemical and Biomolecular Engineering3, who proposed the ratio in 1993 in ‘Measurement of the hydrodynamic surface roughness of non colloidal spheres,’ Phys. Fluids A 1, 52–60.

External links

   * Flow of Wet Granular Materials, Huang et. al, Phys. Rev. Lett. 94, 028301 (2005)
   * David T. Leighton, Department of Chemical and Biomolecular Engineering
   * Role of particle network in concentrated mud suspensions, C. Ancey, Laboratoire d'Hydraulique Environnementale