The effect of the Weissenberg number on a fully-developed flow of dilute polymer solution is numerically examined using Brownian dynamics simulation. The results demonstrate the ability of a mesoscopic approach to predict accurate results in a viscoelastic flow problem using a kinetic theory model: a FENS dumbbell model.

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Interlaced yarns were sectioned one after another to take microphotographs of yarn sections and input positions of every filament into a computer. The yarn cross-sectional area, the average distance and the average intersectional angle between filaments in the cross section were defmed. It was examined how these quantities and the positions of filaments varied along the yarn axis. Furthermore, the structure of interlaced yarns was quantitatively clarified by comparing with those of a raw yarn and a false-twist textured yarn.

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In order to clarify yarn motions in an interlacer, we took photographs of yarns during process with a high speed cine-camera, and analyzed time series data of yarn positions. As a result, the positions where opening parts are processed are limited to the vicinity of the air jet nozzle, and tangling parts are processed on both sides of the opening parts. The yarn motion at the section of the air jet nozzle consists of rotation and traversing the jet axis: A yarn that rotates inside the left semicircle of the yarn duct in the same direction as the air flow for a certain constant time traverses the jet axis to the right semicircle, and continues rotation in the opposite direction. The yarn again traverses the jet axis to the left semicircle after a constant time. The yarn locus is a modified form of letter 8. In the vicinity of the ends of the yarn duct, the yarn motion depends upon process conditions. The yarn rotates inside the left or the right semicircle, or inside the whole yarn duct independently of the air flow direction. Outside the yarn duct, the yam moves in a wider region as the air pressure, the yarn speed or the feed ratio increases.

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Model experiments of blowing air jets on a yarn almost continuously have been made in order to examine how interlaced yarns are processed. Tangling and opening parts are formed intermittently even when a yarn is exposed almost continuously to air jets. When an air jet acts near an already produced opening part, tangling parts at its both ends become firm and cannot become opening parts even if they are subjected to further air jets. Subsequent new tangling and opening parts can be formed at a certain distance from the previous opening part. When the air jet force acting on a yarn is extremely strong, an already produced tangling part is exceptionally destroyed by subsequent air jets.

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