| 摘要: | 本研究旨在探討非球形顆粒體在振動床中之流動行為，比較在相同振動條件下球形與非球形顆粒體在振動床中之流動行為，並探討顆粒形狀對顆粒體在振動床中流動行為與傳輸性質的影響，此外亦研究振動條件(無因次振動加速度與振動頻率)對顆粒體傳輸性質的影響。實驗採用的非球形顆粒體為橢球I形(顆粒長寬比為1.5)，橢球II形(顆粒長寬比為2.0)，膠囊形(顆粒長寬比為2.0)，及雙球形(顆粒長寬比為2.0)，本研究採用改良式粒子追蹤法(Improved Particle Tracking Velocimetry)量測非球形顆粒體之平移及旋轉速度，進而計算相關的傳輸性質，包括平移速度向量，旋轉速度向量，粒子溫度，平移動能，旋轉動能，擴散位移及擾動速度分佈。在固定振動條件(振動頻率25Hz與無因次振動加速度為12.0及振動頻率20Hz與無因次振動加速度為8.0)下，藉由傳輸性質得知顆粒形狀互鎖效應(inter-locking effect)的排序依次為雙球形 > 膠囊形 > 橢球II形，由研究指出擴散係數可以作為衡量顆粒形狀互鎖效應的指標。在固定振動頻率下，顆粒體的速度向量，粒子溫度，動能及擴散位移皆隨著無因次振動加速度的增加而增加。在固定無因次振動加速度下，顆粒體的速度向量，粒子溫度，動能及擴散位移皆隨著振動頻率的減少而增加，以上兩者皆由於振動床所提供的能量增加所致，後者造成的變化較大，這是因為振幅與振動頻率的平方成反比，而與無因次振動加速度成正比。;The purpose of the study is to investigate the flow behaviour of spherical and non-spherical particles in vibrating beds, to compare the transport properties between them, and to explore the influence of particle shape on the flow behavior and transport properties. This study also shows the variations of flow behavior on vibrational conditions (dimensionless vibrational acceleration and vibrational frequency). The granular materials used in vibrating tests were ABS particles including spherical, ellipsoidal I (aspect ratio=1.5), ellipsoidal II (aspect ratio=2.0), capsule (aspect ratio=2.0) and paired particle (aspect ratio=2.0). The Improved Particle Tracking Velocimetry (PTV) was employed to measure the translational and rotational velocities of the non-spherical particles. The transport properties of the particles in a vibrated bed, including translational velocity vector, rotational velocity vector, granular temperatures, translational kinetic energy, rotational kinetic energy, self-diffusion coefficients and fluctuation velocity distributions were analyzed. The experimental results reveal that the degree of the inter-locking effect follows the sequence: paired particle > capsule particle > ellipsoidal II particle. It is pointed out that the diffusion coefficient can be used as an index to represent the inter-locking effect. In the same vibrational frequency, the velocity vector, granular temperatures, translational kinetic energy, rotational kinetic energy and self-diffusion coefficients of the particles increase with dimensionless vibrational acceleration. In the same dimensionless vibrational acceleration, the corresponding transport properties increase with the decrease of the vibrational frequency. Both are attributed to the increasing amplitude, providing more energy for granular assembly especially for the latter. This is that the amplitude is inversely proportional to the square of the vibrational frequency, and is linearly proportional to the dimensionless vibrational acceleration. |
