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Packing Properties of Fibres in the Open-Packed Yarn Mode

Petrulis D., Petrulyte S.

Fibres & Textiles in Eastern Europe

2017

Vol. 25, no. 2 (122)

57--61

Theoretical observations of the packing properties of non-compressible round fibres for two idealized modifications of the open-packed yarn model are discussed. The modifications differ in the method of arrangement of fibres within the cross-sectional ring layer. Modification I has a number of fibres regularly increasing in further layers, and Modification II has the fibres maximum packed in the layers. A procedure for obtaining the number of fibres in the layers of Modification II was proposed. The investigation showed that with the beginning of the 5th layer, the above-mentioned modifications have different packing properties. Because of additional fibres in the layers of Modification II, packing fractions in the layers and yarn obtained were greater if compared with those for Modification I. Analysis of packing properties was made up to 12 layers of the yarn model and also was done for a case of an infinitely large numbers of layers or fibres in a yarn.

W pracy omówiono teoretyczne właściwości upakowania nieściśliwych okrągłych włókien dla dwóch wyidealizowanych modyfikacji modelu przędzy typu „open-packed”. Modyfikacje różniły się w sposobie układania włókien w obrębie warstwy przekroju poprzecznego. Wykazano, że wraz z początkiem piątej warstwy modyfikacje mają różne właściwości upakowania. Analiza właściwości upakowania została wykonana do 12 warstw modelu przędzy oraz w przypadku nieskończenie dużej liczby warstw i włókien w przędzy.

Kinematic model for yarn movement in turbulent air flows

Jungbecker P., Seide G., Gries T.

Autex Research Journal

2008

Vol. 8, no. 4

94--99

In the textile industry a tool is needed that can predict fibre and yarn movement in turbulent air streams. The Institut für Textiltechnik of RWTH Aachen University (ITA) has developed a yarn model that can be used to study the movement of single fibres and yarns in turbulent air flows. The kinematic model is described in this article. Special attention is paid to the aerodynamic forces that determine the flight path of fibres and yarns. The coefficient of drag tangential to the fibre axis ct was studied thoroughly using computational fluid dynamics (CFD). It is shown that the diameter has a strong influence on the wall shear stress. Neglecting this effect for thin fibres can lead to errors in the coefficient of drag of a factor of 500. The turbulence intensity also has an important influence on the boundary layer development, which also determines the coefficient of drag. The assumptions made for the yarn model were tested in an experiment in which yarn flight paths were detected with a high-speed video camera. The comparison to the simulation results confirms the usability of the yarn model.