Abstract:
Surface irrigation is the main irrigation system widely used in Bangladesh. An efficient way of irrigation is the usage of the pressure compensating (PC) emitter (also known as drip irrigation), which reduces both energy and water requirements for irrigation compared to surface irrigation by providing sufficient water at the point of need. There are two types of emitter; namely inline and online emitters. Inline emitters are molded inside a pipe, whereas online emitters are separate devices plugged onto the outer surface of a pipe. Both the flow type and pattern in an online emitter mostly depend on the flow path inside the emitter. However, the resistance to flow in an emitter is required to increase linearly with rising inlet pressure to achieve PC behavior. Manipulation of the flow path area, length, and perimeter are ways to realize this linear increase in resistance. Therefore, the present study emphasizes to evaluate the performance of an existing online emitter both experimentally and numerically. After that, the study continues to focus on designing a new online PC emitter with specific discharge for a predefined range of line pressure. Experiments have been conducted for two different pressure regions, one is high pressure region where the pressure is varied from 2.5 m to 9.5 m of water and another is low pressure regions where the pressure is varied from 1.5 m of water to 2.5 m of water. From the experimental data, the relation between pressure and discharge flow rate is determined. The numerical study is also performed in the said pressure regions, and the pressure distribution and the flow field are visualized. The relation between pressure and discharge flow rate of the emitter is also determined from the numerical results. The comparison of the experimental and the numerical results shows that the emitter works better under the low pressure regions where the numerical results are in good agreement with the experimental results. Finally, the characteristics of the emitters are evaluated for the low pressure regions. The evaluation of the characteristics reveals that the newly designed emitter is most suitable of irrigation in Bangladesh than the existing emitter.
