Definitions and Microscopic Origins

7= shear strain, dimensionless 7= rate of shear = Au/Ay = U (velocity)/ f (thickness), s T = shear stress =/(force)M (area). Pa T = shear viscosity = T/7, Pa s 

FIGURE 7.1 Arrangement for producing laminar, unidirectional shear flow between parallel plates (see Table 7.1). 

Because varies only in the direction y, perpendicular to the direction in which fluid planes slide, this type of flow is also termed a laminar shear flow. The force per unit area is the same everywhere in the fluid and is termed the shear stress 

The rate of change of velocity along y is also constant throughout the fluid 

The ratio of shear stress to shear rate defines the fluid s shear viscosity  

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