本文關(guān)鍵詞：基于EMMS的簡(jiǎn)化雙流體模型及其在氣固流動(dòng)模擬中的應(yīng)用　出處：《中國(guó)科學(xué)院大學(xué)(中國(guó)科學(xué)院過(guò)程工程研究所)》2017年博士論文　論文類(lèi)型：學(xué)位論文

  更多相關(guān)文章： 氣固兩相流動(dòng) EMMS曳力 簡(jiǎn)化雙流體模型 氣固流態(tài)化 多相流

【摘要】：氣固兩相流系統(tǒng)中普遍存在的顆粒聚團(tuán)和氣泡等介尺度結(jié)構(gòu)對(duì)流動(dòng)有著重要的影響。研究這類(lèi)結(jié)構(gòu)的數(shù)值模擬方法主要分為三類(lèi),分別是直接數(shù)值模擬(Direct Numerical Simulation,DNS)、離散顆粒模擬(Discrete Particle Model,DPM)和雙流體模型(Two-Fluid Model,TFM)。對(duì)于工業(yè)裝置的模擬,DNS和DPM需要的計(jì)算量太大,因此主要的模擬方法是TFM。但雙流體模型的模擬精度依賴(lài)于子模型的準(zhǔn)確度,比如衡量固相顆粒之間相互作用的固相應(yīng)力模型以及氣固相間曳力模型等。當(dāng)前廣泛采用的雙流體模型通過(guò)基于顆粒動(dòng)理論的(Kinetic Theory of Granular Flow,KTGF)的固相應(yīng)力模型來(lái)考慮固相顆粒之間的作用,該方法需要額外的計(jì)算量來(lái)迭代求解顆粒溫度的輸運(yùn)方程,同時(shí)也容易帶來(lái)計(jì)算穩(wěn)定性的問(wèn)題。對(duì)于相間曳力的計(jì)算,目前研究者的一個(gè)共識(shí)是需要考慮介尺度結(jié)構(gòu)。此外,許多研究發(fā)現(xiàn),對(duì)于氣固系統(tǒng)的模擬,相間曳力模型比固相應(yīng)力模型更重要。因此,如果將考慮了介尺度結(jié)構(gòu)的EMMS(Energy-Minimization Multi-Scale)曳力與簡(jiǎn)化的固相應(yīng)力模型結(jié)合起來(lái),將有望得到計(jì)算速度快同時(shí)精度也較高的簡(jiǎn)化雙流體模型。如果進(jìn)一步采用穩(wěn)定性更好的數(shù)值離散方法,將能進(jìn)一步提高模型的穩(wěn)定性。在這一思路下,本論文第二章提出了一種簡(jiǎn)化雙流體模型(Simplified Two-Fluid Model,STFM),將固相應(yīng)力模型作了簡(jiǎn)化,同時(shí)耦合了 EMMS曳力。并對(duì)該模型中的兩相動(dòng)量方程進(jìn)行了恒等變形,將兩相的體積分率與相速度進(jìn)行了分離,以避免固相動(dòng)量守恒方程中的奇點(diǎn)問(wèn)題。論文第三章首先介紹了 OpenFOAM(Open source Field Operation And Manipulation)平臺(tái)下有限體積方法的基礎(chǔ),然后詳細(xì)介紹了簡(jiǎn)化雙流體模型在OpenFOAM下的具體實(shí)現(xiàn),并重點(diǎn)闡述了求解固相連續(xù)性方程的MULES(Multi-dimensional Universal Limiterwith Explicit Solution)算法的原理。第四章用三個(gè)不同復(fù)雜度的算例對(duì)簡(jiǎn)化雙流體模型進(jìn)行了驗(yàn)證,總體上講,簡(jiǎn)化雙流體模型耦合EMMS曳力的模擬精度較高,與完整雙流體模型(Full Two-Fluid Model,FTFM)耦合EMMS曳力相當(dāng),但是STFM的計(jì)算速度提高到FTFM的二倍以上。然而,對(duì)于復(fù)雜的工業(yè)裝置,可能同時(shí)存在著多種流域。不同流域可能呈現(xiàn)出截然不同的流動(dòng)特點(diǎn),很難有一套模型能適用于所有流域。為此,本論文第五章提出了一種多區(qū)域簡(jiǎn)化雙流體模型,這種模型能將工業(yè)裝置劃分成不同的區(qū)域并根據(jù)不同區(qū)域的流動(dòng)特點(diǎn)選擇不同的子模型。對(duì)于雙流體框架下的模型,主要的兩種子模型是摩擦應(yīng)力模型和曳力模型。本論文首先考察了不同摩擦應(yīng)力模型在顆粒堆積和密相鼓泡床模擬中的影響,然后考察了不同的曳力模型在不同流域情況下的表現(xiàn)。在此基礎(chǔ)上,本論文開(kāi)發(fā)了能針對(duì)不同流域選擇不同摩擦應(yīng)力模型和曳力模型的多區(qū)域簡(jiǎn)化雙流體模型。此外,為了提高數(shù)值穩(wěn)定性,本論文實(shí)現(xiàn)了一種延遲修正的離散格式,既能保持一階迎風(fēng)格式的穩(wěn)定性,又能達(dá)到二階離散精度。本章最后用此多區(qū)域簡(jiǎn)化雙流體模型對(duì)一個(gè)實(shí)驗(yàn)室尺度的全回路循環(huán)流化床進(jìn)行了模擬,并與之前的單區(qū)域簡(jiǎn)化雙流體模型模擬的結(jié)果進(jìn)行了比較,對(duì)比結(jié)果顯示多區(qū)域簡(jiǎn)化雙流體模型顯著提高了模擬的精度。論文第六章總結(jié)了所取得的成果,并對(duì)簡(jiǎn)化雙流體模型的應(yīng)用前景以及未來(lái)的研究方向提出了展望。
[Abstract]:Common gas-solid two-phase flow system in particle agglomeration and bubble meso structure has an important effect on the flow. The numerical simulation method of this kind of structure is mainly divided into three categories, namely the direct numerical simulation (Direct Numerical Simulation, DNS), discrete particle simulation (Discrete Particle Model, DPM) and the two fluid model (Two-Fluid Model TFM). For the simulation of industrial equipment, computation of DNS and DPM need to be too large, so the simulation method is mainly TFM. but the simulation accuracy of the two fluid model depends on the accuracy of the model, such as the ratio between solid measure solid particles interaction model of stress and gas solid drag force model. Two fluid model widely used based on the granular dynamic theory (Kinetic Theory of Granular Flow, KTGF) of the solid stress model to consider the interaction between solid particles, the method requires Additional computation to iterative particle temperature transport equation, at the same time, it is easy to bring the calculation stability. For the calculation of the drag force, currently a consensus on the need to consider the mesoscale structure. In addition, many studies have found that the gas-solid system simulation, the drag force model is more important than solid the corresponding force model. Therefore, if considering the meso scale structure of EMMS (Energy-Minimization Multi-Scale) solid drag and the simplified stress model combined, will be expected to simplify the calculation speed of the two fluid model has higher precision and faster. If we use more stable numerical discretization method, will further improve the stability of the model. In this way, the second chapter puts forward a simplified two fluid model (Simplified Two-Fluid Model, STFM), the solid stress model was simplified, and at the same time Coupling the EMMS drag force. And the phase momentum equations in the model were identical deformation, the two phase volume fraction and phase velocity were separated to avoid the problem of singularity of conservation of momentum equation of solid phase. The third chapter introduces OpenFOAM (Open source Field Operation And Manipulation) platform based finite volume method then, details the realization of the simplified two fluid model in OpenFOAM, and focuses on solving the continuity equation of solid phase MULES (Multi-dimensional Universal Limiterwith Explicit Solution) algorithm principle. The fourth chapter uses three examples with different complexity of the simplified two fluid model was verified, generally speaking, simulation high precision of simplified two fluid model coupling EMMS drag, and the complete two fluid model (Full Two-Fluid Model, FTFM) EMMS phase coupling drag when, but STFM The calculation speed is increased to two times than FTFM. However, for complex industrial equipment, may also exist in a variety of different river basin. Flow may exhibit different characteristics, it is difficult to have a set of models can be applied to all river basin. Therefore, the fifth chapter puts forward a simplified two fluid model area. This model can be divided into different areas of industrial equipment and according to the flow characteristics of different regions of different sub models. The two fluid under the framework of the model, two seed model mainly is friction stress model and drag model. This thesis investigates different friction stress model in granular and dense drum effect bubble bed simulation, and then examines the performance of different drag force models in different watershed conditions. On this basis, this thesis is developed according to different choice of different basin friction stress model And multi regional drag model simplified two fluid model. In addition, in order to improve the numerical stability, this paper implements a discrete scheme of delay correction, which can maintain the stability of the first order upwind scheme, and can achieve the accuracy of two order discrete. At the end of this chapter, using a simplified two fluid model of the multi area on a laboratory scale the whole loop circulating fluidized bed was simulated, and compared with the previous single area simplified simulation of two fluid model results, the comparison results show that the multi regional simplified two fluid model significantly improves the accuracy of the simulation. The sixth chapter summarizes the achievements, and application prospect of the simplified two fluid model and the future the research direction is put forward.

【學(xué)位授予單位】：中國(guó)科學(xué)院大學(xué)(中國(guó)科學(xué)院過(guò)程工程研究所)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TQ021.1;TQ018

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