Lesson plan
Shields parameter
The Shields parameter, also called the Shields criterion or Shields number, is a nondimensional number used to calculate the initiation of motion of sediment in a fluid flow. It is a form of non-dimensionalization of a shear stress, and is typically denoted \psi or \theta . This parameter has been developed by Albert F. Shields, and is called later Shields parameter. The Shields parameter is the main parameter of the Shields formula. The Shields parameter is given by: : \theta = \frac{\tau}{(\rho_s-\rho) g D}, where * \tau is a dimensional shear stress, * \rho_s is the density of the sediment, * \rho is the density of the fluid, * g is acceleration due to gravity, * D is a characteristic particle diameter of the sediment. The critical shear stress and also the critical Shields number ( \tau_\ast and \theta_\ast ) describe the conditions when the sediment starts moving. Note that the shear stress is a property of the current, while the critical shear stress is a property of the sediment.
Article summary
The Shields parameter, also called the Shields criterion or Shields number, is a nondimensional number used to calculate the initiation of motion of sediment in a fluid flow. It is a form of non-dimensionalization of a shear stress, and is typically denoted \psi or \theta . This parameter has been developed by Albert F. Shields, and is called later Shields parameter. The Shields parameter is the main parameter of the Shields formula. The Shields parameter is given by: : \theta = \frac{\tau}{(\rho_s-\rho) g D}, where * \tau is a dimensional shear stress, * \rho_s is the density of the sediment, * \rho is the density of the fluid, * g is acceleration due to gravity, * D is a characteristic particle diameter of the sediment. The critical shear stress and also the critical Shields number ( \tau_\ast and \theta_\ast ) describe the conditions when the sediment starts moving. Note that the shear stress is a property of the current, while the critical shear stress is a property of the sediment.
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