That, is the velocity of the fluid at the solid surface is zero. This may seem surprising, until you recall that your dishwasher often does not clean well when, for instance, the dishes are coated with cheese. The no slip condition means that the water by itself is not as effective as scrubbing with a solid object, and so many of us wipe the dishes before putting them in a dishwasher. For higher viscosity, the velocity gradient is shallower. Essentially, viscosity opposes the existence of steep velocity gradients .
Fluids are subject to turbulence .
The flow is turbulent when eddies and vortices occur. Fluids lose energy through dissipation in both types of flow. In turbulent flow, energy is required to create the eddies and vortices, resulting in an energy loss by the fluid as a whole. The next section is about Poiseuille's Law . 1996, Kenneth R. Koehler.