The objective of the research was to compose adequate math model of fluid movement at continuous and constant discharge and at decreasing discharge over the length assuming field experiments on the study of discharge-pressure characteristics in drip pipelines of low-pressure irrigation systems. Conventional approaches for determining pressure loss along a pipeline on the basis of Darcy-Weisbach law, experimental data obtained in pilot irrigation plots of All-Russian Research Institute of Irrigation Agriculture, as well as probabilistic and statistical methods of matching the theoretical relations with the results of field study were used. Field assessment of linear losses along the pipeline was done by their successive sum-marizing. For this purpose drip pipeline, which length is l, was conditionally divided by n equal sections. Each section had the length ln and discharge qn, assuming that each section had equal losses of transporting fluid velocity. From the data obtained it follows that the model well adequately, with an error of no more than about 3%, has described pressure losses in drip pipelines at operational length up to 150 m. While the length increasing up to 200 m an error increases up to 16 %. To match the model with field data at operational length of drip pipe-lines greater than 150 m it was proposed to include a coefficient, which considers non-stationarity of fluid mass transporting through the pipeline and equals to 1.1812. The proposed analytical relationships agree with experimental data, and obtained error doesn’t exceed the permissible average statistical error of the experiment.
Keywords: pressure loss over the length, drip pipelines, hydraulic resistance, simulat-ing, variable mass, constant discharge.
