In order to obtain an uniform distribution of water over the sprinkling area with the turning irrigation pipe, which has many orifices along the pipe and rotates alternately to the right and left, ranging from zero to 180° upward, its. desirable operating method has been studied experimentally.
The results obtained are summerized as follows:
1. The trajectory distance of the drops of water jetted from each orifice on the irrigation pipe is comparatively short, because the drops of water encounter with an air resistance proportional to the square of relative velocity during the drops traveling through the air.
2. The distribution of water over the sprinkling area is changed largely with the range of a rotating angle of the irrigation pipe. For example, in case of 180° turning of the pipe (full rotation), it is found that the distribution of water is irregular, for most of the drops of water jetted from orifices at any angle ranging from 20° to 50° and from 130° to 160° fall near the outer edge of the area covered, being followed by the occurrence of the accumulation peak of the drops thereabout. This tendency is especially large at a low pressure of water. However, in case of about 80° turning of the pipe, it is sure that the distribution of water over the sprinkling area is more uniform than that in case of 180° turning, though the maximum trajectory distance decreases slightly. Therefore, 80° turning of the pipe is desirable to obtain an uniform distribution of water as compared with 180° turning. A breaze is useful for an uniform distribution of jetted water.
3. Each orifice should be correctly bored with a drilling machine on the pipe, because uncorrectly bored orifices bring often an irregular distribution of water to the direction parallel to the pipe.
4. If the irrigation pipe is laid at about 1 meter in height, the water distribution and trajectory distance is not influenced by the pipe height. The pipe height should be nearly equal to the plant height lest the jetted water should be intercepted by the stalks or leaves of plants.
