Flow of ground water

Flow through a conduit may be steady or unsteady, uniform or non-uniform, and laminar or turbulento Steady flow refers to conditions in which the velocity at any point remains statistically constant with time; it follows that steady flow in pipes or conduits requires a fixed rate of discharge past any section. In uniform flow, conditions at successive sections must display the same velocity characterístics; in other words, not only must the cross sections be the same, but also residual effects of previous cross-sectional changes must have disappeared. Gases as well as liquids may flow through conduits in a steady, uniform manner if the change in density from section to section is smalI; appreciable density variation, on the other hand, will result in a corresponding change in mean velocity (i.e., non-uniformity of motion), thus requiring thermodynamic as well as mechanical relationships to describe the motion.