Abstract:The paper presents the results of an experimental study carried out to investigate the effect of geometric and hydraulic parameters on energy dissipation and location of the hydraulic jump, with a change in the height of roughness elements and the divergence of walls in different discharges. Experiments were conducted in a horizontal rectangular basin with gradual expansion 0.5 m wide and 10 m long. Four physical models were fixed in the flume. The measured characteristics of the hydraulic jump with different divergences ratio (B = b 1 /b 2 = 0.4, 0.6, 0.8, 1) and the inflow Froude numbers (6 < Fr 1 < 12) were compared with each other and with the corresponding values measured for the classical hydraulic jump. The results showed that the tailwater depth required to form a hydraulic jump and also the roller length of the hydraulic jump and the length of the hydraulic jump on a gradual expansion basin with the rough bed were appreciably smaller than that of the corresponding hydraulic jumps in a rectangular basin with smooth and rough bed. With the experimental data, empirical formulae were developed to express the hydraulic jump characteristics relating to roughness elements height and divergence ratio of wall. Also, the applicability of some empirical relationships for estimating the roller length was tested.
The application pattern for single, stationary spray sprinklers exposed to the wind was modelled to simulate water application in a centre pivot irrigated field. In the model, a dynamic square grid of cells for water application and a static square grid of cells for water collection were defined. The dynamic grid contained the information on the water application pattern of an isolated spray sprinkler, and this followed the motion of the centre pivot lateral. The static grid represented the entire the field, and received water from the dynamic grid at fixed time intervals. Model outputs included the applied water distribution pattern and measures of irrigation uniformity (radial, travelling path and global). A series of experiments using pivoted and single spray sprinklers were conducted simultaneously. The results from the model compared well with field observations. The resulting root mean square errors for the Heermann and Hein uniformity coefficient and the average applied water depth were 0.02 % and 0.08 mm, respectively. Model simulations were carried out to illustrate the effect of wind on irrigation uniformity.
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