方形侵入物形狀縱橫比對垂直振動顆粒床內分離現象之影響

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Title:	方形侵入物形狀縱橫比對垂直振動顆粒床內分離現象之影響
Authors:	吳家榮;Wu, Chia-Jung
Contributors:	機械工程學系
Keywords:	粒子流;振動床;侵入物;巴西豆效應;分離;Granular flow;Intruder;Vibrated bed;Brazil nut effect;Segregation
Date:	2022-07-26
Issue Date:	2022-10-04 12:12:15 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究探討當侵入物(Intruder)質量、體積、密度都相同時，改變方形侵入物縱橫比並置入類二維垂直振動床中的巴西豆分離現象，且為了捕捉顆粒的即時照片以及分析用途，架設高速攝影機以及粒子追蹤測速法PTV(Particle Tracking Velocimetry)來進行後續分析，並探討上升時間以及速度、粒子溫度、擴散係數等顆粒傳輸性質。在進行一系列的實驗與分析後，改變侵入物的縱橫比確實會影響到顆粒分離行為，縱橫比較大之侵入物，在上升過程中較為不易，因此上升至自由表面所需時間較長。此現在也反映在上升速度上，縱橫比越大的侵入物上升速度越慢，這是因為長度較長之侵入物每振盪一次所產生之底部空間較大，背景顆粒需要往下填補的數量增加，然而縱橫比越大的侵入物不只會影響底部面積以及顆粒數的多寡，也會使顆粒上下交換運動受到一定程度的阻礙，就是因為這兩項原因導致了為什麼雖為相同體積密度之侵入物，卻有著不同的上升行為。同時我們也量測粒子溫度來判斷置入不同侵入物後是否會對系統整體動能造成影響，結果發現無論是放置何種形狀的侵入物，其整體系統能量並不會因此而改變。最後，為了能更了解到不同侵入物所帶來之變化，量測侵入物底部的自我擴散係數，可以發現系統內部所接收之能量雖然相同，但由於侵入物縱橫比的影響，導致每個縱橫比不同的侵入物底部有不同的流化程度，進而造成彼此間上升時間的差異。;This thesis investigates the phenomenon of brazil nut effect in a quasi-two-dimensional vertical vibrating bed by changing the aspect ratio of the intruder with the same mass, volume and density. In order to capture real-time photos of particles and analyze them, a high-speed camera was set up and use PTV (Particle Tracking Velocimetry) for subsequent analysis, and the transport properties of particles such as rise time and velocity, granular temperature, and diffusion coefficient were discussed. After a series of experiments and analysis, changing the size of intruder will indeed affect the separation behavior. Intruder with longer horizontal lengths are more difficult to ascend during the process of ascending, so the ascending time is longer than those with shorter lengths. This value is also reflected in the rising speed. The longer the intruder are, the slower the rising speed is. Because the bottom space generated by each oscillation of the longer large particles is larger, and the background particles need to be filled down to increase the number. Long intruder not only affect the number of particles at the bottom, but also hinder the exchange movement of particles up and down to a certain extent. It is because of these two reasons why the particles with the same bulk density have different ascending behaviors.At the same time, we also measured the particle temperature to determine whether the placement of different intruder would affect the overall kinetic energy of the system. It was found that the overall system energy did not change whether long or short intruder were placed. Finally, in order better understand the changes caused by different intruder, the selfdiffusion coefficient at the bottom of the intruder was measured. It can be found that although the energy received inside the system is the same, due to the influence of the size of the intruder, the Intruder have different degrees of fluidization at the bottom, which in turn cause differences in rise time between them.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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