Simulation of Motion of Long Flexible Fibers with Different Linear Densities in Jet Flow

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The movement characteristics of yarn in the profiled reed groove of an air-jet loom can have a great impact on the performance of the fabric. Unstable yarn movement tends to lead to weft defects, as short wefts or weft breaks may occur, which could deteriorate the quality of the final fabric. In this paper, the characteristics of the yarn movement in a profiled reed groove are numerically studied. The arbitrary Lagrangian–Eulerian method is used to solve the two-way airflow–yarn interaction and the yarn is simulated with the ball–socket model. A fluctuation ratio is defined to characterize the unsteadiness of the yarn movement. Our simulation first investigates the effect of the gap ratio of the profiled reed groove (β) on the yarn movement then compares the movements of different yarn kinds. The simulation results indicate that a larger β not only decreases gas leaks (thus saves gas consumption), but also stabilizes the yarn movement. Our simulation results also show that the movement of the yarn of polypropylene is more stable than the other two weft-yarn materials. An experiment is also conducted to validate our numerical results, which shows a favorable agreement between them. Our numerical results of the yarn movement in the profiled reed groove can provide a valuable insight into the optimization of the weft insertion system of the air-jet loom.

Section: Discrete Boundary Of the Profiled Reed Groovementioning

confidence: 99%

mentioning

confidence: 99%

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Analysis of the characteristics of air–yarn coupling movement in the profiled reed groove of an air-jet loom

Jin

Xiong

Cui

2021

Self Cite

“…aimed to drive the long fibers through a combination flow of high-pressure air from a main nozzle and a series of assistant nozzles. 14 The large eddy simulation method was employed to obtain the transient flow field of the turbulent jet, and the Lagrangian bead-rod-chain fiber model was used to predict long flexible fiber motion. Numerical research on the fluctuation and velocity of fibers with different linear densities in the jet was carried out, which provided an optimization option for the air-jet loom to improve the energy efficiency by reasonably arranging the first assistant nozzle.…”

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confidence: 99%

Effect of initial pressure of oblique-blowing airflow and folding-in airflow on yarn tucked-in in the pneumatic tucked-in selvedge apparatus

Liu

Zhou

Cheng

et al. 2021

In this paper, numerical simulation and laboratory experiments were combined to research the tucked-in behavior of the yarn in the pneumatic tucked-in selvedge apparatus, and explore the effect of initial pressure of oblique-blowing airflow and folding-in airflow on yarn tucked-in. This work focused on the motion of a single yarn of which one end was fixed while the other was free. Initial pressures for oblique-blowing airflow and folding-in airflow were set as parameters. A numerical model was developed to simulate the process based on the one-way fluid–structure interaction. Then a laboratory experiment was carried out with the help of a high-speed camera to record the motion behaviors of yarns. The motions were compared with the simulation data and showed that the proposed numerical model can properly replicate the motion of yarn and its points in the airflow field. Each group of yarns with different initial pressures was able to be tucked-in and had an elongation. Increasing the initial pressures of oblique-blowing airflow from 0.3 MPa to 0.4 MPa and folding-in airflow from 0.35 MPa to 0.4MPa shortened the time for the yarn to complete the entire oblique-blowing and tucked-in process by 0.4625 ms, and extended the yarn elongation by 0.151 mm.

“…Furthermore, the modeling of highpressure, high-velocity jets presents additional challenges related to the compressibility of the fluid. One work that considers the interaction between a fiber launched by the main nozzle and the turbulent fluctuations in the main nozzle jet is that of Lin et al 22 In that work the flow field behind the main nozzle exit was simulated by means of a two-dimensional, planar LES. From the flow field, which thus included turbulent fluctuations, the forces experienced by the yarn were calculated using a drag coefficient, formulated as a function of the Reynolds number.…”

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confidence: 99%

Towards simulation of force and velocity fluctuations due to turbulence in the relay nozzle jet of an air jet loom

Delcour

Langenhove

Degroote

2020

This research was aimed at obtaining a first estimation of the effect of turbulent vortices present in the relay nozzle jets of an air jet loom on the weft. To this end a large eddy simulation (LES) model was set up and validated capable of simulating a highly underexpanded jet up to a point sufficiently far from the nozzle exit such that flow features at the weft location could be analyzed. The quality of the LES was evaluated based on several quality criteria as well as by comparing the results with experiments and data from the literature. The results show that for a free jet substantial velocity fluctuations are present at a representative yarn location. By inserting a rigid cylinder at this location, the corresponding force fluctuations on a smooth yarn were also obtained. The research shows that the unsteadiness in the jet is quite substantial, as are the corresponding force fluctuations. These fluctuations could have a profound impact on the yarn motion and should at least be considered when using numerical tools to evaluate the forces on or the motion of a yarn acted on by a relay nozzle jet.