INTRODUCTION This Item provides data that may be used to estimate the speed of propagation of pressure waves@ or wave speed@ in a homogeneous body of fluid contained in a pipe or tunnel@ following a disturbance to the flow. Typical causes of such disturbances are the rapid opening or closure of a valve@ or the run-down of a pump pumping fluid along a pipeline. This Item is the first in a series of Data Items concerned with fluid transients in pipelines and tunnels. The magnitude of the pressure change in a system@ following a disturbance to the flow@ is proportional to the wave speed@ and it is therefore necessary to obtain a good estimate of the wave speed for fluid transient design calculations. The magnitude of the wave speed in a fluid is dependent upon the physical properties of the fluid and the elastic properties of the conduit containing the fluid. The additional elasticity introduced by the expansion or contraction of a conduit with the passage of pressure waves may reduce the wave speed by a significant amount. For example@ the wave speed in a fluid contained in very flexible hoses at low pressures* may be only of the order of 5 to 10 per cent of the wave speed in a large@ unconfined body of the same fluid. Similarly@ the presence of free gases in a liquid may introduce additional elasticity and lead to a reduction in the wave speed. Typically@ in water supply lines at normal conditions@ an accuracy better than+per cent in the wave speed estimate@ and hence the estimate of the pressure change@ may be expected using this Item. The wave speed data presented in this Item are in the form of design charts and simple equations that have been shown to correspond well with experimental data. Typical data for the properties of some liquids and the elastic properties of some commonly used conduit materials are given in tabular form. In Section 3 of this Item@ data are presented for the estimation of the speed of propagation of pressure waves in large unconfined bodies of some common fluids. Simple equations for the estimation of wave speeds in homogeneous@ pure fluid flows in pipes and tunnels are given in Section 4. In Appendix A@ simple expressions for the estimation of the wave speeds in homogeneous liquid/gas mixtures and liquid/solid mixtures are presented. Some data concerning the wave speed in steam at various temperatures and pressures are given in Appendix B. The effects of plastic deformation of the pipe walls upon the wave speed are considered in Appendix C. * In very flexible hoses@ the elastic properties of the pipe (and hence the wave speed in the fluid contained in the pipe) may be dependent upon the internal pressure and the rate of change of internal pressure. Consequently@ great care must be taken in the estimation of the wave speed.
ESDU 83046-1983 history
1983ESDU 83046-1983 FLUID TRANSIENTS IN PIPES AND TUNNELS Speed of Propagation of Pressure Waves