1-29 - BIE 5110/6110 Sprinkle & Trickle Irrigation Fall...

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BIE 5110/6110 Sprinkle & Trickle Irrigation Fall Semester, 2004 Assignment #7 (200 pts) Operating Point for Fixed Sprinkler System Due: 29 Oct 04 Given: A fixed sprinkler system (all sprinklers operate simultaneously) in an orchard. Buried IPS-PVC 1-½” lateral pipes (see Table 8.3 of the textbook). Rainbird ® under-tree M20VH impact sprinklers with 5/64-inch SBN-1 nozzle (see www.rainbird.com for technical specifications). Lateral spacing: S l = 40.00 ft. Sprinkler spacing: S e = 40.00 ft. The field is trapezoidal in shape, as shown below: 800 ft 1,100 ft pump mainline 560 ft 0.10 uphill 0.18% downhill In the above figure, only some of the laterals and sprinklers are shown, but remember that the field area is covered with sprinklers in a fixed, permanent system. There are 27 laterals along the mainline. 1
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2 Note the field slopes along mainline and lateral directions. The suction (upstream) side of the pump has a 4-ft static lift from a pond and 10 ft of 8” PVC pipe (ID = 8.205”) with one 90-degree elbow and a strainer screen at the inlet. The mainline is 8” PVC pipe (ID = 8.205”), and is 1,100-ft long. Sprinkler riser height is: h r = 3.0 ft. A Berkeley model 4GQH pump curve as shown on the following page. You will use the characteristic curve for 1600 RPM. Ignore minor losses along the mainline and laterals. Required: 1. Determine the irrigated area (acres). 2. Develop an equation for sprinkler flow rate (q) as a function of pressure (P), whereby q = K d P x (you determine K d and x based on manufacturer’s data). Note that for a straight-bore nozzle, you would expect x to be very close to 0.5, as in Eq. 5.1a. 3. Determine the number of sprinklers along each lateral, where lateral #1 is the closest to the pump, and lateral #27 is the furthest from the pump. 4. Develop at least five points on the system curve and present those points numerically in a table. You should write a macro (Excel) or computer program to do this (don’t attempt to do it by hand with only a calculator). 5. Plot the system curve points on the attached pump curve graph, and draw a smooth curve through the points. 6. Determine the operating point (Q in gpm & TDH in ft) for this system. 7. Determine the average application rate for the whole field area. Do you work in an organized, neat way. Make comments about assumptions and other technical issues as appropriate. Turn in all your work, including the code for your macro or computer program.
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Solution: 1. The irrigated area is approximately: 0.5(800 560)(1100) A 17.2 acres 43,560 + == Due to the trapezoidal field shape, and the fact that there are 27 laterals at S l = 40 ft, the effective irrigated area is slightly less than 17.2 acres.
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This note was uploaded on 03/01/2012 for the course BIE 6110 taught by Professor Sprinkle during the Fall '03 term at Utah State University.

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1-29 - BIE 5110/6110 Sprinkle & Trickle Irrigation Fall...

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