Toward three-dimensional modeling of the interaction between the air flow and a clamped–free yarn inside the main nozzle of an air jet loom

Abstract

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.

Three-dimensional fluid-structure interaction simulations of a yarn subjected to the main nozzle flow of an air-jet weaving loom using a Chimera technique

“…The yarn shape was also compared qualitatively to those from experiments at several time instants. Later Osman, Delcour et al 20 carried out 3-dimensional, 2-way FSI-simulations for a yarn fixed at the main nozzle inlet using an ALE approach.…”

“…Experimental data for the case with the yarn clamped at the main nozzle inlet was obtained from the experiments performed during the research of Osman, Delcour et al 20 . A description of the experimental setup is provided in this section for completeness.…”

“…Nevertheless, the main calculation has been performed on Mesh B to maintain a reasonable computational time. This mesh is already twice as fine as the one used in previous research (Osman, Delcour et al 20 ). In that research an increase in mesh density entailed a reduction in physical time that could be simulated due to more severe mesh degradation.…”

“…Clamped-Free yarn: Comparison to ALE Osman, Delcour et al 20 performed simulations for a clamped-free yarn using an ALE approach. Results were compared to experiments on a quantitative and qualitative basis.…”

“…This peak is tracked and in the final frame (14.7 ms) it is located at point R. The distance between P and R divided by the time in between those snapshots yields the wave speed. To avoid a difference in mesh resolution with the previous work 20 the Chimera simulation considered is the one performed on the coarsest grid (See section "Mesh Sensitivity") in this section only. The exact time instants vary slightly as to more accurately observe the motion of crests and troughs.…”