Simulation of air flow–yarn interaction inside the main nozzle of an air jet loom

Self Cite

In air-jet weaving looms, the main nozzle pulls the yarn from the prewinder by means of a high velocity air flow. The flexible yarn is excited by the flow and exhibits high amplitude oscillations. The motion of the yarn is important for the reliability and the attainable speed of the insertion. Fluid-structure interaction simulations calculate the interaction between the air flow and the yarn motion and could provide additional insight into yarn behavior. However, the use of an arbitrary Lagrangian–Eulerian approach for the deforming fluid domain around a flexible yarn typically results in severe mesh degradation, vastly reducing the accuracy of the calculations or limiting the physical time that can be simulated. In this research, the feasibility of using a Chimera technique to simulate the motion of a yarn interacting with the air flow from a main nozzle was investigated. This methodology combines a fixed background grid with a moving component grid deforming along with the yarn. The component grid is, however, not constrained by the boundaries of the flow domain allowing for large deformations with limited mesh degradation. Two separate cases were investigated. In the first case, the yarn was considered to be clamped at the main nozzle inlet. For the second case, the yarn was allowed to move axially as the main nozzle pulled it from a drum storage system.

Section: Several Models and Simulation Methodologies Aimed At Modellimentioning

confidence: 99%

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

Delcour

Peeters

Degroote

2019

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“…To complete this section, an estimate of the forces on a yarn can be obtained from the velocity field by using a force coefficient. Osman et al 18 reported a longitudinal force coefficient of 7e-05 and an orthogonal force coefficient of 7.64e-04 for a cotton yarn of 104 tex. Using these force coefficients, the fluctuation in the y-and z-direction would reach up to approximately 0.47 N/m with, at that location, an x-force of approximately 0.55 N/m.…”

Section: Analysis Of Velocity Fluctuations Without Yarnmentioning

confidence: 99%

“…This corresponds to a drag coefficient for a smooth cylinder of approximately 1 (see for example Welty et al 40 ). From the drag coefficient the transversal force coefficient (as employed by Osman et al 18 ) can be derived by multiplying it with the yarn diameter. This results in a transversal force coefficient of 7.2e-4 m. Multiplying this force coefficient by the dynamic pressure based on a density ($1.2 kg/m 3 ) and the RMSD value of the transversal velocity (31.7 m/s based on Figure 12) yields an estimate for the amplitude of the transversal force oscillations of 0.443 N/m for a smooth yarn.…”

Section: Analysis Of Force Fluctuations On Yarnmentioning

confidence: 99%

“…Nevertheless, FSI simulations have already been used to study air-yarn interaction. 2,[15][16][17][18][19][20] Concerning air jet looms the FSI research has mainly focused on the interaction between the main nozzle flow and the weft. To the best of the authors' knowledge no FSI research has been performed on the interaction between a weft and the flow from the relay nozzles.…”

mentioning

confidence: 99%

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

Delcour

Langenhove

Degroote

2020

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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.

“…Aiming at the fiber suspensions in air jet spinning nozzles, Guo et al 14 presented a numerical model in which the filament was regarded as a continuous bead-connected chain. Oneway and two-way coupling algorithms were compared by Osman et al 15 to simulate the motion of a single fiber during the weft-insertion process. Pei et al 16 simulated the stretching, bending, and twisting deformations of flexible fibers in a wall-bounded fluid flow with a finite Reynolds number.…”

mentioning

confidence: 99%

Numerical and experimental study on the joint forming mechanism in the pneumatic splicing process

Zhou

Liu

et al. 2019

This study presents an investigation on the joint forming mechanism of pneumatic splicing by numerical and experimental methods. A one-way coupling numerical model concerning interaction between fluid and filaments was established to simulate the complex motion of a flexible body in a spiral flow field. The airflow field in the splicing chamber, which contributes to longitudinal and normal aerodynamic force along a filament regarded as a digital chain composed of a series of interconnected rods, was obtained by a two-equation turbulent computational fluid dynamics model. Contact-friction behavior within filaments was also taken into consideration. An iterative algorithm was adopted to update the displacement of filaments and the corresponding aerodynamic force. A high-speed visualization test bench was built to record the sequence motion of filaments in the splicing process. The splicing mechanism within flexible filaments was identified by comparison between the experimental data and numerical results. The filament portion located in the homolateral rotating channel with respect to orifice is blown to bent by the jet airflow. It contributes to a frontal area in the axial airflow direction, causing the filament to be retracted toward its fixed end. Meanwhile, the portion in the contralateral rotating channel tries to wrap around the opposite filaments due to the spiral airflow. The interaction between filaments generates the contact force and related friction force, which commonly resists the retracting force exerted on the homolateral filament portion. The competition between the two forces determines whether the joint can be formed. Furthermore, the influence of the overlapping length on splicing behavior was discussed.