In air jet looms, the weft yarn is transported from the prewinder to the reed by means of an air flow. In this work, the motion of a yarn inside a main nozzle during the first stage of an insertion process is modeled and analyzed. In this stage, the weft yarn is clamped at one side and free at the other side. Therefore, the deformation waves of a clamped–free yarn are modeled. A three-dimensional, two-way, fluid–structure interaction simulation has been performed in which the yarn is represented as a flexible cylinder and the arbitrary Lagrangian–Eulerian technique is employed. The results of the simulation have been compared quantitatively and qualitatively with experiments. It was, however, not possible to match the initial position and stress state of the yarn in the simulations to that in the experiments. This causes large differences between the simulated and measured yarn positions and wave characteristics, especially at the beginning. The agreement between experimental and simulated wave characteristics notably improves as time progresses, but substantial differences remain. Analyzing the overall motion of the yarn inside the main nozzle shows that the mixing region, where the shocks are located, can be considered as an excitation point. In this point, the aerodynamic normal forces are high if the yarn is not located on the axis of the main nozzle. All deformation waves start from the mixing region and propagate along the yarn.
The main nozzle of an air jet loom plays an essential role in the weft insertion process. This role involves sucking the weft yarn from the prewinder and launching it into the reed. Simulating the dynamic behavior of the weft yarn inside the main nozzle involves fluid–structure interaction (FSI). In this work, one-way and two-way FSI simulations of air flow–yarn interaction inside a main nozzle have been performed. A three-dimensional model of the flexible weft yarn, consisting of a chain of line segments, and a two-dimensional axisymmetric model of the supersonic flow have been developed and coupled to perform these simulations. The results of the simulations are compared quantitatively and qualitatively with experimental results. Good agreement has been found between the results of the two-way FSI simulations and the experiment. The coupled fluid and structure models provide an effective numerical tool to optimize the geometry of the main nozzle based on the calculated motion and speed of the weft yarn.
3Pneumatic yarn splicing is a technical process for joining two yarn ends together. The 4 process involves injecting compressed air into a splicing chamber. Inlet pressure and 5 chambers slope determine the main parameters affecting this process. In this paper, large 6 eddy simulation (LES) of the flow field in four selected splicing chambers is carried out. 7The chambers are used for splicing ends-together yarns. The results of these simulations are 8 analysed to investigate first the effects of the inlet pressure. Second, the effects of the 9 geometry of the chambers on the flow field inside the splicing chambers are determined. 10These effects are studied and analysed to interpret the experimental results, which have 11 been obtained using the same splicing chambers. This provides further insight into the 12 parameters which are important to obtain good splicing characteristics. It is demonstrated 13 that the volume of the splicing chamber and the location of the air inlet channel play crucial 14 roles in the splicing of the end-together yarns.
This research analyzes the interaction between fibers and the air jets that are used to accelerate them in fiber processing industries. Typically, supersonic flow is used to achieve sufficiently high thread speeds. However, this flow contains shocks and expansions, resulting in large longitudinal variations in force on the thin and flexible thread. Consequently, a complex fluid-structure interaction (FSI) occurs between the supersonic air flow and the thread. In this research, the fluid-structure interaction between a supersonic air flow and a thread is studied numerically using three-dimensional simulations. The thread is represented by a smooth and flexible cylindrical body. The displacement of the thread is calculated for a given traction on its surface using a finite element structural dynamics code. The compressible flow around the thread is calculated using a finite volume computational fluid dynamics (CFD) code, using the arbitrary Lagrangian-Eulerian (ALE) framework to account for the thread deformation. In these partitioned simulations, the kinematic and dynamic equilibrium conditions on the fluid-structure interface are satisfied using a coupling algorithm. Two coupling algorithms are compared and the influence of numerical parameters is investigated. The fluid-structure interaction simulations reveal transversal running waves in the thread. By comparing the speed of these waves with the propagation speed of the shock waves in the tube, it can be concluded that these phenomena are not related.
The noise generated from an impact forming machine arises mainly from structural vibrations and consequently accurate determination of the modal characteristics of the machine is necessary in order to bring about design modifications with the aim of reducing noise levels. Various methods of dynamic testing are applied to a high speed forming machine structure. It is found that the modes of vibration can be successfully identified by impulse tests, with the force pulse generated either by operation of the machine or by means of a hand held hammer.
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