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The motion of the liquid front during impregnation of non-crimp fabrics has been considered by using Sethian’s level set method. Particular attention is put on the creation of bubbles at the liquid front and a virtual 3D model mimicking biaxial fabrics has been built for this purpose. The saturated fluid flow is governed by the Navier–Stokes Equations and Darcy law, while capillary pressure has been accounted for at the liquid flow front and continuity maintained. The influence of perturbation in the bundle geometry has been investigated. Local correlations of the dimensions of neighbouring gaps formed between the bundles are of paramount importance. Focus is on inter-bundle bubbles. An existing model for bubble dynamics is used based on a probabilistic approach for bubbles moving, splitting, merging, and dissolving. The same approach was used for intra-bundle bubbles, the difference being that their motion appears to be much slower. The obtained void fractions of inter-bundle bubbles at different vacuum levels applied at the liquid flow front are compared to those from real mouldings with a high degree of conformity. 相似文献
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Anna-Lena Ljung Vilnis Frishfelds T. Staffan Lundström B. Daniel Marjavaara 《Drying Technology》2013,31(7):760-773
Drying of a porous bed of iron ore pellets is here considered by modeling a discrete two-dimensional system of round pellets. As a complement to the two-dimensional model, a continuous one-dimensional model enabling fast calculations is developed. Results from the discrete model show that the temperature front advances faster in areas with large distances between the pellets. In areas with low flow speed, the temperature of the pellets increases with a relatively slow rate. The water inside these pellets will therefore remain for a long time. The continuous model fits the discrete model very well for a regular distribution of equal-sized particles. A discrete model with irregular packing will, compared to the continuous model, show a larger variation in the distribution of temperature and moisture content in the final phase of drying. 相似文献
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