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Building a Rain Simulator
In the Center’s activity planning meeting for the 2004-2005 period held in January 2004, the initiative of building a rain simulator that would make it possible to carry out field experiments on the response of the Region’s soil physical variables when exposed to several extreme precipitation events was proposed (within the scope of the work plan agreement subscribed by the Chilean and Flemish Governments and UNESCO). |
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The simulator was built by Professor Edmundo González O. (egonzal@userena.cl), of the University of La Serena, with the assistance of his technical team and the support granted by the University of Ghent, through Dr. Donald Gabriels, the scientific counterpart of the Flemish government for the CAZALAC project and Eng. Koen Verbist from this university.
Technical note from the simulator builder
A summary of the main technical aspects to be considered is presented below according to the experience of building this equipment. A more detailed report can be found in the technical note available in pdf format.
Operation requirements
Size |
Height: |
Variable range from 1.2 to 2.5 m. |
Width: |
1 – 1.2 m . |
Length: |
For 10 nozzles maximum |
Distance between nozzles: |
1 m |
Kind of Sprinkler: |
Spray nozzles (Full cone Unijet system). |
Nozzle lines between 4, 6, 8, y 10 meter long and 1 meter wide are required.
Other Specifications |
Area covered: |
A maximum area of 10 m2 can be covered |
Rain intensity required: |
100 mm/h, for 30 minutes. |
Pump power: |
When maximum intensity is required, a pump driving from 3,000 to 5,000 liters per hour has been considered. However, it is recommended that the irrigating lines be equipped with a 10000 l/hour pump to allow future extensions. |
System Operating Pressure: |
Depending on the rain intensity, the system must operate within a 0.7 a 1.3 Bar pressure from the last nozzle in the line. |
General Layout of the Rain Simulator |
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Hydraulic System
The hydraulic system was designed to meet the requirements established in point 1.2. With this purpose, the main pipe was designed with a maximum of 10 sprinklers in line with a 1 meter distance between each nozzle. The flow v/s pressure ratio used for the nozzles was obtained from discrete information supplied by the manufacturer, as indicated in the attached table. |
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Pressure (Bar) |
Flow (L/min) |
0.3 |
3.7 |
0.5 |
4.6 |
0.7 |
5.3 |
1.0 |
6.2 |
2.0 |
8.5 |
3.0 |
10.1 |
4.0 |
11.5 |
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The best design for a 32 diameter C-6 PVC pipe was obtained from the above data and once the expense line was drawn from the above table. The system was tested for the required pressures and the pressure drop difference between the first and last sprinkler did not exceed 0.03 bar. Therefore, sprinklers operate evenly, with no considerable flow variations.
Hydraulic System Detail |
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Hydraulic System Supplementary Elements
Amount |
Description |
1 |
1 HP -1”x1” Motor Pump |
1 |
2,000 l. Tank |
1 |
1” Flow meter |
100 m |
1” Plastic hose |
1 |
Hose carriage |
Metallic structure
The hydraulic system is supported by 10 separate metallic mini towers. Each mini tower consists of a tripod is equipped with a center rod that is adjustable to different heights and extensible metallic arms. The tripod is the main bearing of the structure and its legs may be adjusted at different heights and angles to easily secure it in an uneven ground. The main elements considered when manufacturing the mini tower are shown in the figure below.
Metallic Structure |
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Main elements of metallic structure
Main elements of metallic structure |
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Accessories and additional elements
Amount |
Description |
2 |
13 mm. Screw wrench |
1 |
1.8 m. Stick |
1 |
10 m. Folding measuring tape |
1 |
10 m. Measuring tape |
1 |
Water level |
1 |
20 m. Plastic fabric |
1 |
Plastic sheets or plates (0.25 x 2 cm) |
2 |
Shovels |
2 |
Waterproof plastic sheets (2 x 2 m) |
2 |
Flumes |
100 |
Plastic receptacles (for rainwater catchment) |
100 |
Weights to secure receptacles from wind |
1 |
Plastic cylindrical measuring receptacle (500 ml) |
2 |
Chronometers |
4 |
500 ml receptacle to catch run off water |
2 |
Mallets 0,5 kg |
100 |
Small capped pots to obtain samples |
100 |
Plastic bags to take humidity samples |
1 |
Hand bit (small) to take soil samples |
100 |
Label makers |
1 lt |
Coloring matter (potassium manganate) |
Start Up
Two field tests were performed to check the simulator operation, where Mr. Guido Soto, CAZALAC’s executive Director and Dr. Donald Gabriels from the University of Ghent, Belgium were present. Tests were carried out on Wednesday 22 and Thursday 23, July 2004. The first test was run in an even place and basically consisted of checking equipment mounting and commissioning. Two short 10 and 15 minute tests were done at a 1 Bar constant pressure in the last nozzle. Intensities were measured in tests.
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