【摘要】：顆粒物質是大量的宏觀粒徑大于微米的固體顆粒的聚集,是與連續(xù)態(tài)物質相區(qū)別的另一大類物質形態(tài),往往表現(xiàn)出體系內部異質不均結構、整體對力非線性響應等特點,并發(fā)生無序到無序、unjam到jammed等結構變化,是凝聚態(tài)物理前沿研究領域和新增長點。顆粒體系為遠離平衡態(tài)的耗散體系,其造成系統(tǒng)能量損失的主要原因是：顆粒之間的相互作用以非彈碰撞和摩擦為主。因此維持體系的運動就要依靠外部的能量輸入,常見的驅動形式有重力、撞擊、激振、剪切等。在這些外加的作用下,系統(tǒng)會呈現(xiàn)出類似于固體、液體及氣體的特性,而顆粒物質自身離散的特性又使它們跟連續(xù)介質形態(tài)有很大的差異。以至于有的學者建議將顆粒物質看做除了傳統(tǒng)的固體、液體、氣體以外的“第四種物質聚集形態(tài)”。 顆粒物質的系統(tǒng)尺度可以從微米以上跨越六個量級,因此在自然界、工程實踐和人類生產(chǎn)生活中廣泛存在。顆粒物質的研究涉及多個領域：工農(nóng)業(yè)、建筑業(yè)、制造業(yè)、醫(yī)藥食品業(yè)等。許多自然現(xiàn)象(山體滑坡、浮冰流、雪崩等)和工業(yè)生產(chǎn)過程(散態(tài)物質的輸運、加工等)也與顆粒物質的運動規(guī)律密切相關。因此,對顆粒物質的運動規(guī)律的探究具有重要的社會效益和經(jīng)濟價值。 本文主要針對顆粒物質類液和類氣特性設計了顆粒流動和振動試驗,并通過試驗觀察、理論建模和計算模擬相結合的手段對其特性進行分析。希望對理解顆粒物質在非靜態(tài)條件下的物理特性提供一些有益的借鑒,對工程上顆粒物質的管道輸送、多道匯聚、流量優(yōu)化等問題提供一些理論性的指導。本文的主要研究內容有： 考慮到實際的顆粒運輸管道往往是受多個瓶頸的制約(比如出口收縮、管道拐彎等),我們設計了雙瓶頸斜槽流實驗,用來研究多瓶頸對系統(tǒng)相變和流量的影響。實驗中,系統(tǒng)發(fā)生了稀疏流一密集流的相轉變。在相變過程中,出現(xiàn)了一個稀疏態(tài)和密集態(tài)都可能存在的雙穩(wěn)區(qū)域。我們對雙穩(wěn)現(xiàn)象出現(xiàn)的原因進行了研究。我們發(fā)現(xiàn)是入口初始流量波動和上下瓶頸共同作用的結果。我們引入了復雜網(wǎng)絡方法對初始儲料倉內堆積顆粒的力網(wǎng)絡進行分析,發(fā)現(xiàn)疏松堆積和密集堆積對系統(tǒng)初始流量的影響。再通過對上下瓶頸進行離散元模擬,成功得到雙穩(wěn)發(fā)生的范圍,模擬結果跟實驗結果一致。最后,我們研究了槽道傾角對系統(tǒng)的影響,并給出優(yōu)化系統(tǒng)流量的建議。 顆粒流與車輛交通流有許多相似的物理特性,我們做了一個雙道匯聚的顆粒斜槽實驗,來類比車輛交通中匝道進入主道的情形。通過主(側)道比側(主)道寬兩組不同的對比實驗,發(fā)現(xiàn)兩道的入口流量不同可以使系統(tǒng)發(fā)生從稀疏到密集的相轉變,并且存在四個相態(tài)。這點跟車輛交通流中的匝道系統(tǒng)有相似之處。對雙道流量變化進行分析,發(fā)現(xiàn)兩組不同情況下,出口流量會出現(xiàn)一次或兩次流量突降,這種現(xiàn)象在交通流中未被發(fā)現(xiàn),可能是顆粒流的獨特現(xiàn)象。通過實驗,我們還發(fā)現(xiàn)匯聚區(qū)域存在一個發(fā)生稀疏流到密集流轉變的臨界體積分數(shù)(?)＝0.63±0.03。兩道匯聚的研究希望對多道(N3)顆粒流匯聚問題的研究提供一定的借鑒。 顆粒物質受激振動會表現(xiàn)出類氣特性,系統(tǒng)內顆粒之間碰撞頻繁,非線性、耗散性尤為突出,其中一種具體表現(xiàn)是顆粒聚簇(clustering)和顆粒時鐘(GranularClock)現(xiàn)象。我們先對之前學者關于顆粒氣體雙倉振動體系的研究進行概述,接著介紹我們新發(fā)現(xiàn)的顆粒雙倉振動中的聚簇一顆粒時鐘(GC-Clustering)共存現(xiàn)象。當我們把雙倉容器寬度增大以后,系統(tǒng)出現(xiàn)了水平偏析現(xiàn)象,并且此偏析存在兩種不同模式,導致系統(tǒng)出現(xiàn)顆粒時鐘態(tài)或者聚簇態(tài)。這兩種狀態(tài)是在同一個振動強度下隨機發(fā)生的,從實驗觀察結果來看呈現(xiàn)一種“跳跳停�！钡默F(xiàn)象。我們對此問題進行了細致的研究,通過改變顆粒數(shù)目比、半徑比、盒子寬度等試驗條件找出了聚簇一顆粒時鐘現(xiàn)象的存在區(qū)域,并引入了一個單位時間轉換概率P修正了一般的顆粒雙倉系統(tǒng)的Flux Model,定性的重現(xiàn)了該實驗現(xiàn)象。此部分工作對顆粒氣體非線性特性和顆粒系統(tǒng)的隨機性進行了有益的探索。 本文研究了顆粒物質的流動和振動兩個主要方面的動態(tài)特性問題,較側重于顆粒物質的獨特動態(tài)行為和其非線性物理特性。通過本文的研究,進一步加深了對顆粒物質系統(tǒng)復雜性機理的認識,并對自然界和實際工程中涉及的顆粒物質的加工和輸運問題提供有益的借鑒。
[Abstract]:Particulate matter is the aggregation of a large number of solid particles with a macro particle size larger than the micron. It is another large type of substance which is different from the continuous state matter. It often shows the heterogeneity of the structure in the system, the overall response to the force nonlinear response, and the disorder to disorder, unjam to jammed, and so on. It is the research of the condensed matter physics. The field and the new growth point. The particle system is a dissipative system which is far from the equilibrium state. The main cause of the system energy loss is that the interaction between particles is dominated by non elastic collisions and friction. Therefore, the movement of the maintenance system depends on the external energy input, and the common driving forms are gravity, impact, excitation, shear, etc. In addition, the system presents the characteristics similar to the solid, liquid and gas, and the discrete characteristics of the particles make them very different from the continuous medium. Some scholars suggest that the particles be regarded as the "fourth substance aggregation forms" other than the traditional solid, liquid and gas.
The systematic scale of particulate matter can span six orders of magnitude above the micron, so it exists widely in nature, engineering practice and human life. The research of particulate matter involves many fields: industry, agriculture, construction, manufacturing, medicine and food. Many natural phenomena (landslides, floating ice flows, avalanches, etc.) and industrial processes The movement of particulate matter is closely related to the movement of particulate matter. Therefore, it is of great social and economic value to explore the movement of particulate matter.
In this paper, the particle flow and vibration test are designed for the liquid and gas like properties of particles. The characteristics are analyzed by means of experimental observation, theoretical modeling and calculation simulation. It is hoped to provide some useful reference for understanding the physical properties of granular materials under non static conditions, and to the particle material in engineering. It provides some theoretical guidance for pipeline transportation, multi-channel convergence and flow optimization.
Considering that the actual particle transport pipeline is often restricted by multiple bottlenecks (such as exit contraction, pipe turning, etc.), we designed a double bottleneck flow experiment to study the effect of multiple bottlenecks on the phase change and flow of the system. In the experiment, a phase transition of a dense flow of sparse flow is taken place in the experiment. In the process of phase transition, a dilute occurs. We have studied the causes of the bistable phenomenon. We find that the initial flow fluctuation and the upper and lower bottlenecks are the result of the joint effect. We introduce the complex network method to analyze the force network of the accumulated particles in the initial storage bin, and find loose accumulation and dense heap. The effect of the product on the initial flow of the system. Then through the discrete element simulation of the upper and lower bottlenecks, the range of the bistability is successfully obtained. The simulation results are in agreement with the experimental results. Finally, we study the influence of the slot angle on the system, and give a suggestion to optimize the flow of the system.
There are many similar physical characteristics between the particle flow and the vehicle traffic flow. We have done a double channel converged granular slots experiment to compare the ramp into the main road in vehicle traffic. Through the two different comparison experiments of the main (side) side (main) path width, it is found that the difference in the inlet flow of the two channels can cause the system to occur from sparse to dense. Phase transition, and there are four phase states. This is similar to the ramp system in the traffic flow. Analysis of the two channel flow changes shows that the flow rate will occur once or two times under the two different conditions. This phenomenon is not found in the traffic flow and may be a unique phenomenon of the particle flow. Through experiments, we It is also found that there is a critical volume fraction (?) (?) = 0.63 + 0.03. two channel convergence of a sparse flow to dense flow transition in the aggregation region, and hopes to provide some reference for the study of the problem of multichannel (N3) particle flow convergence.
The stimulated vibration of particulate matter will show gas like characteristics. The collisions between particles in the system are frequent, nonlinear and dissipative, and one of them is particle cluster (clustering) and particle clock (GranularClock). First, we summarize the previous scholars' research on the dual chamber vibration system of particle gas, and then introduce it. We found the coexistence of cluster and particle clock (GC-Clustering) in the newly discovered particle double chamber vibration. When we increase the width of the double chamber container, the system appears horizontal segregation phenomenon, and there are two different modes in the system, which leads to the emergence of the particle clock state or the cluster state. The two states are in the same vibration intensity. At random, we present a "jump stop" phenomenon from the experimental observation results. We have studied the problem in detail. By changing the particle number ratio, the radius ratio, the box width and other experimental conditions, we found the existence region of the cluster one particle clock phenomenon, and introduced a unit time conversion probability P correction. The Flux Model of the general particle double chamber system reproduces the experimental phenomenon qualitatively. This part of the work makes a useful exploration of the nonlinear characteristics of the particle gas and the randomness of the particle system.
In this paper, the dynamic characteristics of the two main aspects of the flow and vibration of particulate matter are studied, which are more focused on the unique dynamic behavior and the nonlinear physical properties of the particles. Through this study, the understanding of the complex mechanism of the granular material system is further deepened, and the particulate matter involved in the natural and practical engineering is also discussed. It provides a useful reference for the processing and transportation problems.
【學位授予單位】：中國科學技術大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：TB53

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