ABSTRACT
In unsteady or non-steady flow, the mean values at a particular point do vary with time. Countless small variations add considerably to the difficulties of solving problems that involve unsteady flow. This chapter considers certain problems of unsteady flow are amenable to analytical solution. The initiation of flow in a pipe-line is governed by inertia pressure. In some types of hydraulic machine the inertia pressure required to accelerate a column of liquid may be so large that the pressure at the downstream end of the column falls to the vapour pressure of the liquid. The chapter ana;yses the rate at which a change of pressure is transmitted through the fluid. Since the velocity and pressure in a pipe subject to pressure transients are continuous functions of position and time, they are described essentially by partial differential equations. Many of the problems associated with pressure transients may be circumvented by the use of a surge tank.
