Визначення оптимальної середньої швидкості руху рідини в перерізах збірного дренажного трубопроводу змінного діаметра

An analysis of the operating conditions of pressure collecting drainage pipelines has shown that such conduits are typically considered as channels with a constant cross-section along their length, operating under variable discharge. In the initial sections of these pipelines, the average velocities of the main flow are relatively low (below permissible limits), which often leads to the deposition and accumulation of significant amounts of soil particles in the initial sections. In the final sections, the average flow velocity becomes excessively high, causing an increase in head losses. Therefore, the problem of determining the optimal value of the average fluid velocity along the length of a collecting pipeline is relevant. Taking into account the above, the purpose of the present study is to develop a calculation methodology for determining the optimal average fluid velocity along the length of pressure collecting drainage pipelines with a variable (increasing) cross-section. In this work, based on a dimensionless analysis of a system of differential equations describing fluid flow with variable discharge in pressure collecting drainage pipelines with an increasing cross-section, a methodology for calculating the optimal average fluid velocity is proposed. During the analysis, the second term in the differential equation of variable discharge, representing head losses associated with the effect of fluid attachment along the pipeline length, was neglected, as it has negligible influence on the final computational results. The study considers the concept of a conditionally infinite collecting pipeline or a finite pipeline with an infinitely permeable lateral surface. The key parameters determining the change in flow rate along the collecting drainage pipeline are taken as the collector resistance coefficient ζlcol and the generalized drainage collector parameter Аcol, which accounts for its structural and filtration characteristics. As a result, a simple and practical method has been obtained for determining the maximum average velocity in the final section of the collector, taking into account the variable diameter and the non-uniform inflow distribution along its length.