1-27 - BIE 5110/6110 Sprinkle Trickle Irrigation Fall...

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BIE 5110/6110 Sprinkle & Trickle Irrigation Fall Semester, 2004 Assignment #5 (100 pts) Minor Losses & Pumps Due: 13 Oct 04 Given: A rectangular field to be sprinkler irrigated There will be four laterals, two on each side of the mainline All of the periodic-move laterals will move in the same direction At the beginning of an irrigation, two laterals are at the upstream end of the mainline (first hydrant) and the other two are at the mid-point of the mainline The nominal hydrant diameter, and the inside diameter, is 4 inches Each lateral irrigates ¼ of the field area, and each is 600 ft in length Required lateral inlet pressure head is P l = 44 psi The mainline will be 5-inch aluminum (see Table 8.4), with hydrant values spaced at S l = 30 ft along the 1,320-ft length of the mainline The first hydrant is located 30 ft from the beginning of the mainline, and the last hydrant is 1,320 ft from the beginning of the mainline The sprinkler system will operate 12 hrs/day, and the irrigation interval during the peak-use period is 7 days The gross depth to apply per irrigation is 1.9 inches The mainline slopes downhill at a uniform slope of 0.18% See the table in Chapter 8 for the roughness height of aluminum pipe See Table 11.1 for minor loss coefficients, K r Required: What is the field area, in acres? What is the system capacity, in gpm? Will the velocity in the mainline acceptable, or too high? Use the Darcy-Weisbach equation for pipe friction loss Make a graph of required (minimum) pressure at the upstream end of the mainline as a function of lateral position, such that the minimum lateral inlet pressure (for each lateral position) is exactly 44 psi This means that one pair of laterals will have exactly 44 psi inlet pressure, while the other pair will have a slightly higher inlet pressure, and this will be the case for each lateral position Note that there will be 1,320/(2*30) = 22 different positions lateral for each pair of laterals On the graph, you can call the lateral positions “1,” “2,” “3,” … “21,” and “22.” Make note of any assumptions and of references which you use to obtain data

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1-27 - BIE 5110/6110 Sprinkle Trickle Irrigation Fall...

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