ABSTRACT
In laminar flow, individual particles of fluid follow paths that do not cross those of neighbouring particles. There is nevertheless a velocity gradient across the flow, and so laminar flow is not normally found except in the neighbourhood of a solid boundary, the retarding effect of which causes the transverse velocity gradient. This chapter considers steady laminar flow between plane boundaries that move relative to one another while remaining parallel and the same distance apart. A dashpot is essentially a device for damping vibrations of machines, or rapid reciprocating motions. The viscosity of a fluid cannot be measured directly, but its value can be calculated from an appropriate equation relating it to quantities that are directly measurable. In an ideal viscometer, the flow of the fluid under test would be completely determined by its viscosity. In any method of measuring viscosity it is important to maintain the fluid at a constant and known temperature.
