Development of numerical modelling techniques for air-jet weft insertion

In an air-jet loom a yarn (called the weft) is inserted in between perpendicular threads (the warp threads) by means of an air flow to create a woven fabric. By using an air flow to propel the weft, no mechanical component has to travel back and forth through the machine. This allows air-jet looms to attain very high production speeds, making them well suited for mass production. However, in order to attain a high insertion speed, a high air velocity is required. To this end, highly pressurized air is employed which results in complex flow patterns with shocks and expansion waves. Furthermore, due to the absence of a mechanical component that guides the weft, its motion is rather unconstrained and mainly governed by its interaction with the air flow. Because of the aforementioned complexities it is difficult to accurately model the air flow and weft motion with purely analytical or semi-empirical models. Therefore, in this thesis, numerical techniques are developed and applied to analyze the weft insertion process. Depending on the required computational resources, these numerical simulations can be used in optimization procedures or to obtain a better understanding of the insertion process and the influence of parameters thereon in order to further improve the efficiency and/or productivity of these looms