COMPARATIVE ANALYSIS OF TEST RESULTS OF DRIP LATERALS WITH CIRCULAR AND ELLIPTIC CROSS SECTION

Abstract

Lately, the drip irrigation systems find more and more application, which led to the production of a new type of drip laterals – with flat to elliptic cross section and comparatively small thickness of the wall – from 0.2 to 0.9 mm, compared to the conventional ones with circular cross section and wall thickness over 1 mm. The main advantage of the first type is that they are comparatively cheap and are offered in the form of small rolls, the length of the hose being from 500 to 3500 m which makes their transportation to warehouses, assembly and disassembly very convenient. With the smaller thickness of the walls, the laterals have almost clenched form and are intended to be used for one irrigation season, while those with higher thickness, with elliptic form, may be used for several seasons. The inside welded emitters are flat and have a very small water-stopping head area compared to the annular water-stopping cross section of the cylindrical drippers in the conventional circular type of laterals. This is connected with the smaller head losses in the movement of water in them, which is an important advantage. The paper presents and analyses the results of the hydraulic test of the two types of drip hoses – with circular and elliptic cross section, in order to find the head losses for different lengths - 40, 60 and 80 m and heads in the beginning of 6, 8, 10, 12, 14 and 16 m, as well as the coefficients of uniformity for both types. The following hoses of both types were tested: JUNIOR, with circular cross section and internal diameter of 13.8 mm, nominal diameter 16 mm, thickness of wall 1.1mm, cylindrical type of drippers with a flow rate of 2.1 l/h and interval between nozzles 0.30 m (Irritec, Italy); DP Line (D5), with elliptic cross section, with the same sizes and intervals but with a wall thickness 0.6 mm and flat type of drippers (Irritec, Italy). The results indicate that irrespectively of the elliptic form of the cross section which is with a very small hydraulic radius, the head losses are almost equal to those with the circular cross section with cylindrical drippers, which is due to the minor head losses because of the flat nozzles in them. The values of the absolute coefficient of uniformity and the calculated one according to the method of Christiansen for all options are presented. The test is performed for zero slope, while modelling is performed for slopes 1% and 2%. The analysis of the data indicates that for zero slope of the terrain the increase of head leads to increase of the coefficients of uniformity for the three tested lengths of laterals; for 1% are observed very small tendencies for reduction of those coefficients, while for 2% the coefficients have higher values compared to the other slopes, again with slightly expressed tendency for change. The higher values in the 2% slope are due to the additional head caused by the geodetic level difference of the terrain.