| Summary: | 碩士 === 元智大學 === 化學工程與材料科學學系 === 95 === Previously, Cheng and Chang (2005) has developed a 3-dimensional model of the Twill weave metal screen by analyzing the woven screen to obtain the smallest repeating unit and then set up a 3-dimensional CFD model of the repeating unit. In this study, their model was further investigated to obtain complete penetration curves at three face velocities rather than penetrations at three particle diameters. It was shown that the predicted penetration agree with particles less than 1.0 ?慆 but deviates from those experimental data obtained by Chen (2003). The discrepancy was the largest when the face velocity was 1 cm/sec, while those of 5 and 7 cm/sec agree with experimental data rather consistently with an error within 10%. Further attempt was undertaken to investigate the possible causes for the discrepancy observed for the 1 cm/sec case. An investigation of deviation between predicted penetrations for single and multiple repeating units suggested a single repeating unit may be sufficient for the prediction of penetration. Also, the investigation of the effect of initial particle velocity on penetration for the 1 cm/sec case showed the initial particle velocity affects the predicted penetration of particles larger than 1.0 ?慆 in a significant way. For all initial particle velocities investigated herein, none of them overlaps with the experimental data completely. Lastly, the effect of diffusion and gravitational setting were also examined.
The final aim is proofing the results of Chen (2003) by simulating. For saving the memory neglects the effect of boundary layer and simplifies the metal woven screen to single repeating unit. Comparing the penetration of experiment and simulation fits the theory by Hinds (1999) or not. Then paralleling the repeating unit to makes sure there is no influence for boundary effect. Finally, observing the penetration of different face velocity and particle diameter and influences cause by particle diffusion coefficient, gravity, and particle velocity.
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