【正文】 . Bridging the gap between this geometry and that of an elbow or tee was the introduction o the concept of the equivalent stagnation length. As a particle approaches the boundary, that is the pipe wall, its normal velocity to that surface will decrease until it reaches zero, however some particles with sufficient momentum will strike that surface with some velocity before obtaining that normal velocity of zero. The distance between the point where the particle’s normal velocityy begins to reduce and the wall is defined as the stagnation length. Selection of the equivalent stagnation length targets equivalence between that length and the length of the normal impingement scenario that results in similar erosion rates. This stagnation length concept is shown schematically in Figure : Multiphase Annular Flow and LowLiquid Flow (LLF) Regimes Annular and LowLiquid Flow Conditions in Vertical Pipes Gasliquid twophase flow involves the simultaneous and interacting flow of gas and liquid. This type of flow is an extremely plex phenomenon。 however, the models were only valid for certain conditions and based on limited experimental data. The Erosion/Corrosion Research Center (E/CRC) at The University of Tulsa developed an erosion prediction model for use over a broad range of operating conditions that accounted for geometry type, size, and material。 however, after a critical size which is reported to be 100 181。懇請(qǐng)閱讀此篇論文的老師、同學(xué)，多予指正，不勝感激！外文原文SAND EROSION MODEL IMPROVEMENT FOR ELBOWS IN GAS PRODUCTION,MULTIPHASE ANNULAR AND LOWLIQUID FLOWCHAPTER 2LITERATURE REVIEW This chapter outlines the literature reviews as follows. First, backgrounds of the mechanism of solid particle erosion as well as the erosion model used in this work are presented. Secondly, a general overview of multiphase annular and lowliquid flows with emphasis on literature associated with modeling in vertical and horizontal flows is presented. Thirdly, the literature associated with previous large and smallscale erosion xperimental work in singlephase and multiphase flow conditions is presented. Fourthly, the literature associated with experimental characterization of multiphase flows in pipelines and elbows is presented with emphasis on the use of WireMesh Sensors(WMS). Finally, a summary of the factors affecting sand erosion in annular and lowliquid flow conditions is presented Mechanism and Modeling of Solid Particle Erosion Solid Particle ErosionThe process by which wall material is removed due to particle impacts is referred to as solid particle erosion. Erosion is different from wear in that there is a fluid contribution to the mechanical action that is producing wear.The mechanism of erosion is very much dependent on the process parameters involved. Properties of the impacting particles, target materials and environment have a major influence on the mechanism of erosion. In the literature, various schools of thought exist for the mechanism of erosion. For the erosion of ductile metals, Finnie (1958) and Bitter (1963) reported that, at oblique impact, erosion occurs by the cutting action of the particle irrespective of its shape and size. Hutchings (1979) agreed with the cutting mechanism at oblique impact。沒有張老師、孫老師的辛勤栽培、孜孜教誨，以及兩位師兄的指導(dǎo)和改正，就沒有我論文的順利完成。這除了自身努力外，與各位老師、同學(xué)和朋友的關(guān)心、支持和鼓勵(lì)是分不開的論文的寫作是枯燥艱辛而又富有挑戰(zhàn)的。 Benjamin. CFD analysis of UAVs using VORSTAB, FLUENT, and advanced aircraft analysis software.[D]. The University of Kansas[19] Dakin。得到數(shù)據(jù)如下表。、壓強(qiáng)圖取z=,z=,z=,z=,z= ke模型出口70mm,z= ke模型出口70mm,z= ke模型出口70mm,z= ke模型出口70mm,z= ke模型出口70mm, z= ke模型出口70mm,z=、繪制壓強(qiáng)折線圖。 Contours對(duì)話框設(shè)定點(diǎn)擊Display。 Z= 點(diǎn)擊Greate,創(chuàng)建等值面。 Grid Display 對(duì)話框點(diǎn)擊Display。依次點(diǎn)擊File—Read Caseamp。 ，出口為70mm時(shí)的殘差圖 ，出口為90mm時(shí)的殘差圖依次點(diǎn)擊File—Write—Date，保存數(shù)據(jù)。依次點(diǎn)擊Slove—Iterate，打開Iterate對(duì)話框。依次點(diǎn)擊Slove—Monitors—Residual。、求解初始化。 出口邊界條件點(diǎn)擊 OK 。 Velocityinlet對(duì)話框在Velocity Magnitude（m/s），其余設(shè)置保留默認(rèn)。 Boundary Conditions對(duì)話框。 Database Materials對(duì)話框 Database Materials對(duì)話框中選擇waterliquid，點(diǎn)擊Coppy。 Models對(duì)話框Model選擇ke模型，各項(xiàng)設(shè)置保留默認(rèn)，點(diǎn)擊 。 Smooth/Swap Gird對(duì)話框點(diǎn)擊Swap.信息反饋窗口中顯示，再點(diǎn)擊一次Swap，使得Number face swapped 變?yōu)?，圖 、建立求解模型。 FLUENT 軟件主界面、依次點(diǎn)擊File—Read—Case,（）。，進(jìn)行后處理等。(2D或3D等)。(Translators)—轉(zhuǎn)換其他程序生成的網(wǎng)格，用于FLUENT計(jì)算。另外用戶還可以定制或添加自己的湍流模型；、程序的結(jié)構(gòu)FLUENT程序軟件包由以下幾個(gè)部分組成：——用于建立幾何結(jié)構(gòu)和網(wǎng)格的生成。網(wǎng)格變形方式有三種：彈簧壓縮式、動(dòng)態(tài)鋪層式以及局部網(wǎng)格重生式。、FLUENT軟件的應(yīng)用CFD商業(yè)軟件FLUENT，是通用CFD軟件包，用來模擬從不可壓縮到高度可壓縮范圍內(nèi)的復(fù)雜流動(dòng)。在Name中填入BOUNDARY, Type選擇WALL, ，.點(diǎn)擊Apply.、保存文件，并到處網(wǎng)格。、打開生成的網(wǎng)格，單機(jī)Operation中的命令按鈕，選擇Zones中的，在彈出Specify Boundary Types對(duì)話框。、GAMBIT網(wǎng)格的生成、單機(jī)Operation ,選擇Mesh中的，選擇，打開Mesh Volumes對(duì)話框，點(diǎn)擊Apply，生成網(wǎng)格，、在Global Control 01欄中選擇 EXAMINE MESF 命令按鈕，打開Examine 。 在Geometry中選擇，選擇，打開Move/Copy Volumes 對(duì)話框，（因?yàn)槭橇鶄€(gè)柵欄所以每個(gè)旋轉(zhuǎn)角度為60度，首先選擇Volume4,點(diǎn)擊Alppy,再選擇Volume5進(jìn)行下一次復(fù)制，依次復(fù)制出5個(gè)柵欄）。點(diǎn)擊Apply， 線成面、面成體。（115），（116），（117），（118）點(diǎn)擊Apply,、線成面。點(diǎn)擊Apply,， 出口為70mm,矩形柵欄切面平移 出口為90mm,矩形柵欄切面平移 出口為70mm, 矩形柵欄在圓盤上的投影,矩形柵欄在圓盤上的投影、按1步在建一個(gè)尺寸相同的矩形face13,矩形柵欄切面平移,矩形柵欄切面平移按2步平移face13到圓柱切面上。 Move/Copy Volumes 對(duì)話框設(shè)置點(diǎn)擊Apply，、按第三步的方法新建一個(gè)高度為3mm。步驟如下：、用鼠標(biāo)左擊操作工具欄（GAMBIT建模界面右上角）GEOMETRY；、在GEOMETRY子操作板上用鼠標(biāo)右擊VOLUME命令按鈕，在彈出下拉菜單中，左擊按鈕，打開Create Real Brick對(duì)話框 Real Brick 對(duì)話框、在Create Real ，其余保留默認(rèn)值，設(shè)置如圖點(diǎn)擊Apply，這時(shí)在左下角將顯示信息說您已經(jīng)創(chuàng)建一個(gè)物體“”,鼠標(biāo)左擊右下角的，此時(shí)在圖形窗口上顯示如圖 ，建立兩個(gè)高度為3mnm,半徑分別為50mm和35m的圓柱（或半徑分別為50mm和45mm的圓柱），如圖所示。、特點(diǎn)，通過多種方式直接建立點(diǎn)、線、面、體，而且具有強(qiáng)大的布爾運(yùn)算能力，ACIS內(nèi)核已提高為ACIS R12。GAMBIT通過它的用戶界面（GUI）來接受用戶的輸入。今后，人們一方面將根據(jù)工程技術(shù)方面的需要進(jìn)行流體力學(xué)應(yīng)用性的研究，另一方面將更深入地開展基礎(chǔ)研究以探求流體的復(fù)雜流動(dòng)規(guī)律和機(jī)理。電子計(jì)算機(jī)的出現(xiàn)和發(fā)展，使許多原來無法用理論分析求解的復(fù)雜流體力學(xué)問題有了求得數(shù)值解的可能性。力學(xué)家經(jīng)過多年努力，創(chuàng)造出許多數(shù)學(xué)方法或技巧來解這些方程組（主要是簡(jiǎn)化了的方程組），得到一些解析解。流體運(yùn)動(dòng)在空間和時(shí)間上常有一定的限制，因此，應(yīng)給出邊界條件和初始條件。流體力學(xué)中最常用的基本模型有：連續(xù)介質(zhì)（見連續(xù)介質(zhì)假設(shè)）、牛頓流體、不可壓縮流體、理想流體（見粘性流體）、平面流動(dòng)等。、CFD的處理方法CFD軟件的一般結(jié)構(gòu)由前處理、求解器、后處理三部分組成。在給定的參數(shù)下用計(jì)算機(jī)對(duì)現(xiàn)象進(jìn)行一次數(shù)值模擬相當(dāng)于進(jìn)行一次數(shù)值實(shí)驗(yàn), 歷史上也曾有過首先由CFD 數(shù)值模擬發(fā)現(xiàn)新現(xiàn)象而后由實(shí)驗(yàn)予以