Hydraulic experiment in non-pressure pipeline made of polymer material

Introduction. To solve the problem of water shortage for irrigation in the city of Kerbala (Iraq), for the first time, a decision was made to use treated wastewater from urban wastewater treatment plants. Transportation of water from treatment facilities to irrigated lands is carried out through a pipeline in a non-pressure mode. Using the Water Card simulation model, the optimal pipe diameters for two flows, 1200 and 2,200 mm, were selected. The capacity of the existing treatment plant is 1.16 m3/s or 100,000 m3/day, and after the introduction of new treatment facilities, the flow rate will increase to 4.63 m3/s or 400,000 m3/ day. The aim of the work was to experimentally confirm the choice of the optimal diameter of the pipes and determine the hydraulic characteristics of the flow in it. In this regard, in laboratory conditions, experimental studies of the hydraulic characteristics of the flow in a polyethylene pipe with a diameter of 100 mm in the range of slopes (0.005–0.03), with fluid flow in non-pressure, were carried out. Using the theory of hydrodynamic similarity, the results of experimental data were recalculated for pipe diameters of 1200 and 2,200 mm. As field data, when modeling hydrodynamic similarity, the results obtained in the simulation model are taken into account. In world practice, there is experience in the reuse of treated wastewater, but water is supplied to the place of consumption in most cases through open channels. For the first time, pipes of large diameters are used in this work, which requires a more detailed study of the hydraulic parameters of the flow in it. Materials and methods. Using the theory of hydrodynamic similarity, the results of experimentally obtained hydraulic parameters were calculated for plastic pipes with a diameter of 1200 mm at a water flow rate of 1.16 m3/s and 2,200 mm at a flow rate of 4.63 m3/s. Results. Conducting experimental studies and recalculating experimental data from a similar model to a full-scale object (the results obtained using the Water Card simulation model are used as a full-scale object) using the Froude method with similarity coefficients made it possible to obtain the following values of average flow rates, hydraulic friction coefficients λ, Chezy coefficients C, Reynolds numbers and other flow characteristics when filling the pipeline from 0.1 to 0.8 for pipes with diameters of 1200 and 2,200 mm. Conclusions. Conducting laboratory studies to determine the hydraulic characteristics of a polyethylene pipeline with a diameter of 100 mm as a model and substantiate the hydraulic similarity of the model and nature, in the form of plastic pipes with diameters of 1,200 and 2,200 mm, respectively, will allow designing a gravity system of main pipelines for transporting treated wastewater in the city of Karbala (Iraq). Further, the data of the simulation model are used as field data.