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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 IPSPVC 1½” lateral pipes (see Table 8.3 of the textbook).
•
Rainbird
®
undertree M20VH impact sprinklers with 5/64inch SBN1 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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•
Note the field slopes along mainline and lateral directions.
•
The suction (upstream) side of the pump has a 4ft static lift from a pond and 10 ft of 8”
PVC pipe (ID = 8.205”) with one 90degree elbow and a strainer screen at the inlet.
•
The mainline is 8” PVC pipe (ID = 8.205”), and is 1,100ft 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
straightbore 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.
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.
 Fall '03
 Sprinkle

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