POLYFLOW - What draw ratio can be reached in fibre spinning ? What take-up velocity ?
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Let us consider a 3D fibre spinning situation, where the die has a rectangular cross section of 2x0.08 units. With a short fibre (short computational domain), is it possible to obtain a draw ratio higher than 10000 or higher than 100 in each directions? The answer is yes. Let us consider a simple example involving the suggested 3D fibre spinning process. When considering both planes of symmetry, we obtain a cross-section of 1x0.04. Let us consider a die length of 1 and a fibre length of 2. The material has a viscosity of e.g. 1000; the inlet flow rate is 0.04 on this fibre quarter, and corresponds to an average velocity of 1. For running such a case, two evolutions can be needed (optimisation has not ben attempted). A first evolution is applied on the slipping coefficient, which ranges from 1 to 1e7, under an exit velocity of 1. A ramp function is used, with (a,b) = (0,1e-7) and (c,d) = (1,1). Simultaneously and beyond, an evolution scheme is applied to the take-up velocity, with an exponential funciton f(S) = exp(S). Let us note here that S ranges from 0 to 11, for the purpose of the selected evolution schemes. When S=11, we have a take-up velocity of about 60000. A quick inspection of the results reveals a deviation of 0.4% in terms of cross section area. The data files as well as the grid are stored in the attached file Fibre.zip; the calculation should be performed with the p3rc file attached. Also, results (for CFD-Post) can be found in the file Fibre_results.zip while an image is shown in the attached file Fibre_drawing. Only the last result file is provided. |
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