Variation of the collective drainage pipelines parameters when passing the transit flow

Simple and convenient dependences for calculating basic hydraulic and design characteristics of pressure collecting horizontal drainage pipelines operating in the presence of transit flow, in which the fluid collection along the path occurs in the filtration mode, are presented in the paper. They are based on the analysis of a system of differential equations that describe the fluid motion in such pipes. The solutions are based on the assumption that the member, which takes into account the effect of the flow variation along the pass, is neglected. The concept of a fictitious infinitely long collecting drainage pipeline or a pipeline with an infinitely large amount of the pipe walls permeation is used in the analysis. It is assumed that the actual flow at the end of this pipelines is replaced by a conditional flow, which is collected at the fictitious end section of the pipeline. The flow in the end section of the fictitious pipes is assumed to be zero. The introduced assumptions allow to use formulas for calculation of the mentioned pipelines with a certain approximation which are applied at calculation of pipelines operation without transit. These dependences allow to calculate the effect of transit flow on the hydraulic characteristics of the collecting drainage pipelines.