- 學位論文
間隙流體及顆粒大小對滾動圓筒中穩態顆粒流形成之影響
Effects of Interstitial Liquid and Sphere Size on the Development of a Steady Granular Flow in a Rotating Drum
摘要
本論文針對不同大小、同材質的乾、溼顆粒體在滾筒中暫態(transient)運動行為作探討，實驗過程以高速攝影機拍攝流場完整之影像，並以圓形霍夫轉換(Circular Hough Transformation)作為顆粒體中心定位的依據，搭配粒子追蹤測速法(particle tracking velocimetry)及瞬時空間平均，以求得顆粒混合體於滾筒內部之平均行為。所探討的混合體性質包括安息角、流動層厚度、體積分率、分離強度、顆粒溫度等重要參數。此外，並著重探討共存黏性液體對這些乾顆粒動態行為之影響。實驗結果顯示無論是純小球、純大球，還是大小球混合的情況下，增加滾筒轉速都會得到較大的最大安息角。在相同轉速但不同間隙流體的情況下，溼顆粒的速度分布會比乾顆粒要來的小。而在分離現象方面，溼顆粒的分離現象會比較晚發生，無論是乾、溼顆粒，在低轉速的情況下，分離現象也會比較晚發生。
並列摘要
This thesis focuses on the unsteady motion of dry and wet granular flow in a rotating drum using solid spheres of identical material but two different sizes. The mixture bulk behavior was recorded by a high-speed digital camera and the obtained digital images were analyzed for the segregation phenomenon. Particular efforts were made to identify possible liquid effects on modifying the bulk behaviors. To achieve this, the algorithm of an existing Circular Hough transformation routine was modified to locate the motions of the two species. The mixture bulk behavior was obtained by coarse-graining spatial average. The investigated bulk behavior include repose angle, flowing layer thickness, volume fraction, intensity of segregation and granular temperature. The repose angle increased with increasing rotating speed. At the same rotating speed but different interstitial liquid, wet granular bulk velocity profile will smaller than dry granular. About segregation phenomenon, wet granular will occur delay than dry granular. At the low rotating speed condition, no matter dry or wet granular, the segregation phenomenon will occur lately.