So-called ‘drippers’ are mostly used for irrigating large areas such as in greenhouses, fruit and arable farming, as well as in parks. Plants grow better with an even water supply. By injecting water drops directly near the root, little water is lost unused through evaporation or being blown away. Furthermore, fertiliser can be introduced into the soil along with the water.
The heart of every ‘dripper’ is the labyrinth, which consists of a small channel (cross-section < 1mm) with many curves and obstacles. The geometric shape of this labyrinth determines the water output at the prevailing pressure in the supply line.
The ‘dripper’ is manufactured using an injection moulding process. Since an injection mould entails high production costs, usually only a few different labyrinth variants can be tested to obtain the desired relationship between pressure and water volume flow. Therefore, it is necessary, before a prototype is built, to predict this relationship as accurately as possible based on the labyrinth geometry. FlowMotion was therefore tasked with developing new design methods to improve this prediction.
First, with the help of visualisations and measurements, the flow phenomena in the labyrinth of an enlarged model were studied and the influence of geometry changes on the flow resistance was determined. These results were used to conduct numerical simulations (Computational Fluid Dynamics - CFD). Flow simulations were carried out for a wide variety of labyrinth geometries and the relationship between pressure and volume flow was determined. The most promising shapes were then transferred back to the enlarged model and experimentally tested.
This combination of experimental and numerical methods has provided many important results. Primarily, this includes the expansion of knowledge regarding the flow through the labyrinth and how it can be influenced. Secondly, by reducing the number of prototypes required, a reduction in manufacturing costs has also been achieved.
