Shear rate is a measure of the rate at which a fluid is sheared or "worked" during flow
. In more technical terms, it is the rate at which fluid layers or laminae move past each other
. Shear rate is determined by both the geometry and speed of the flow
. Some key aspects of shear rate include:
- Definition : Shear rate is the rate of change of velocity at which one layer of fluid passes over an adjacent layer
- Units : Shear rate is measured in reciprocal seconds (s-1) or 1/s
- Simple Shear : In the case of simple shear, the shear rate is calculated as the velocity gradient between the moving and stationary plates, divided by the distance between the plates
. For example, if the moving plate is 1.0 cm/s and the stationary plate is 0.0 cm/s, the shear rate would be (1.0 cm/s - 0.0 cm/s) / 0.1 cm = 10 s-1
- Viscosity : Viscosity is the resistance to flow, which is related to the shear rate and shear stress by the equation τw = ẏ × μ, where τw is the shear stress, ẏ is the shear rate, and μ is the viscosity of the fluid
- Non-Newtonian Fluids : For non-Newtonian fluids, there are different constitutive laws depending on the fluid, which relate the stress tensor to the shear rate tensor
Shear rate is an important parameter in various fields, such as fluid mechanics, rheology, and biochemistry, as it helps to understand the behavior of fluids and their interaction with solid surfaces
