Context

Everyday experience teaches us that fluids resist being moved, and that this resistance varies greatly according to the nature of the fluid. For example, it's much harder to move a spoon through honey than through a glass of water. The physical quantity that characterizes this resistance is the fluid's viscosity. This is defined as follows. In the case of a simple shear flow, as shown in figure 1 a, a layer of fluid of thickness h is sheared between a fixed and a moving plate at constant speed U. In the stationary regime, the velocity profile is linear and allows the shear rate $\dot{\gamma }=U\text{/}h$...