TO THE HYDRAULIC CALCULATION OF PRESSURE DRAINAGE PIPELINES, OPERATING IN DISTRIBUTION REGIME

Abstract

A system of two differential equations which describes the movement of fluid in a pipe with a variable flow rate and the conditions for the fluid outflow through the walls of drainage pipelines into the surrounding soil is considered. It is reasoned that the second term in the original equation, which takes into account energy losses associated with a flow rate variation along the length, can be neglected without a substantial error. The considered system is reduced to dimensionless form by introducing original variables. The coefficient of collecting drainage pipeline resistance «ζl» and the generalized parameter «A», which take into account the structural and hydraulic characteristics of the considered flow, are two main parameters used in the analysis. The concept of an infinitely long drainage pipeline (a pipeline with an infinite walls filtration capacity) is introduced in the article. Also it is noted that such pipeline will have a maximum throughput comparing to pipes of the same diameter but limited length. Quite simple and practical calculated dependencies for the determination of the nature of flow rate variation and pressure drop along the length of the pipeline were received on the basis of the conducted analysis. Important characteristics of pressure distribution pipelines were calculated on the basis of offered formulas. Corresponding graphical dependencies were built for visibility. In particular, graphs of the flow rate variation at the end of the distributor, depending on the design and filtration characteristics of the «soil-drain» system, are presented. Graph that shows the dependence of the variation in the flow rate distribution unevenness along the length of the drainage pipe at various ​​hydraulic conductivity values of the surrounding soil is important for understanding the drainage pipelines particularity. The necessity to take into account the nature of the flow rate connection unevenness along the length for obtaining reliable results for real drainage pipelines calculation is demonstrated.