三角形结构对液膜流动特性影响的数值模拟

基于VOF方法,利用CFD软件FLUENT对倾斜壁面上二维气-液两相流进行数值模拟,分析了三角形高度和结构间距均为1mm的6种尺寸壁面上的液膜流动特性,获得了三角形结构的壁面上液膜自由液面的分布图以及不同结构宽度w对液膜流动特性的影响规律。结果表明:与平壁面上液膜流动相比,三角形结构壁面上液膜自由液面位置随三角形结构呈规律性变化;在三角形结构壁面上,气体漩涡存在于液膜和壁面之间,当三角形结构宽度w改变时,漩涡的形状和位置均发生变化。     

Numerical Simulation of a Mathematical Model for Dry/Wet-Spun Nascent Hollow Fiber Membrane

NomenclatureCsh—solventconcentrationinanascenthollowfiber ( g·cm-3 )fo—dragcoefficientattheexternalsurfaceofanascenthollowfiberF( γE)—materialfunctiondefined (Eq .( 2 ) )g—gravitationalfunction ( 980cm·s-2 )G(Csh)—materialfunctiondefined (Eq .( 2 ) )Ho—thecombinedreciprocalradiiofthecurvaturesattheouterskinofthenascenthollowfiber (cm-1)L—air gapdistance (cm )Ri—innerradiusofanascenthollowfiber (cm)Ro—outerradiusofanascenthollowfiber (cm)R′o,R″o—thefirstandsecondorderderivat…     

用于乙醇-水分离的SA-PVA/PSF中空纤维渗透汽化复合膜

Using polysulfone (PSF) hollow fiber ultrafiltration membranes as the substrate, sodium alginate (SA) and polyvinyl alcohol (PVA) blend solutions as the coating solution, and maleic anhydride (MAC) as the cross-linked agent, SAPVA/PSF hollow fiber composite membranes were prepared for the dehydration of ethanol-water. The effects of different sodium alginate concentration in the coating solutions and different operating temperatures on pervaporation performance were investigated. The experimental results showed that pervaporation performance of the SA-PVA/PSF composite membranes for ethanol-water solution exhibited a high separation factor although they had a relatively low permeation flux. As SA concentration in SA-PVA coating solution was 66.7% and the operating temperature was 40 ℃, SA-PVA/PSF hollow fiber composite membrane (PS4) had a separation factor of 886 and flux of 12.6 g/(m2·h). Besides, SA-PVA/PSF hollow fiber composite membranes (PS3 and PS4) were used for the investigation of the effect of ethanol concentration in the feed solution on pervaporation performance.     

水平与垂直PES中空纤维超滤膜组件分离性能的研究

1Introduction Generally,ultrafiltration(UF)asaseparationtech nologyofhighefficiencyandlowenergyconsumption haswidelybeenappliedinvariousindustries.Inin dustrialapplications,therearesixbasicUF modules[1]:(1)tubular,withinnerchannel diameters>4mm;(2)hollowfibers,withinnerdia metersof0.2-3mm;(3)plateunits;(4)spiral woundmodules;(5)pleated sheetcartridges;and(6)rotarymodules.However,hollowfiberUFmoduleis oneofmostimportantmodulesbecauseofitshigh areapackingdensity.Besides,UFtechnologyalsois us…     

基于Mathematica7.0下构建数学模型求解最优化问题

研究利用Mathematica7.0求解导数应用中的最值问题。分析了求解最优化问题的数学模型和Mathematica7.0设计最值的操作步骤,并列举实例进一步说明使用该数学软件是解决工程技术、经济等领域遇到最优化问题的有效途径。     

A mathematical model of symmetry based on mathematical definition

Tolerance is imperative for seamless integration of CAD/CAM (Computer Aided Disign/Computer Aided Manufacture) which is just a text attribute and has no semantics in present CAD systems. There are many tolerance types, the relations between which are very complicated. In addition, the different principles of tolerance make study of tolerance difficult; and there may be various meanings or interpretation for the same type of tolerance because of the literal definition. In this work, latest unambiguous mathematical definition was applied to study, explain and clarfy: (1) the formation and representation of tolerance zone, and (2) the formation and representation of variational elements; after which, the mathematical models of symmetry of different tolerance principles and different interpretations were derived. An example is given to illustrate the application of these models in tolerance analysis. Project supported by the National Natural Science Foundation of China for Innovation Research Groups(No.60021201) and NSFC(Nos.59705022 & 69973045).     

对过度反应现象进行数据挖掘的数学模型

对证券市场过度反应现象的研究是行为金融学的一个重要研究方向。文章讨论了过度反应现象的数学描述，并建立了一种以研究过度反应现象的数据挖掘算法为目标的数学模型。用我国A股市场1994．1．3至2004、12．31年的全部个股数据进行实证分析的结论是：在我国股票市场，投资者的投资行为对好消息存在过度反应现象。     

紧急医疗救援方案的数学模型

选择最佳救援方案是在面对各种突发性紧急医疗救助事件时需要考虑的首要问题,在一些落后偏远地区尤其重要.应用线性规划的方法,对某一医疗救援实例进行了具体分析,通过建立数学模型并使用Lingo软件求得最优解,得到最佳救援方案.     

二维轴对称电子回旋共振等离子体磁场的数值模拟

本文根据大连理工大学三束材料改性国家重点实验室的电子回旋共振(ECR)微波等离子实验装置,结合等离子体源中的各种物理参量,采用一种简便快捷的方法在计算机上对ECR等离子体的磁场位形进行了数值模拟,数值模拟结果表明在共振区磁场强度的值达到最大值,这与实验结果一致.     

关于高师数学模型课及其教学的一些思考

讨论了高师开设数学模型课程的意义,明确了数学模型课程的教学侧重点,给出了一些行之有效的教学方法．     

Numerical simulation of bubble chaotic motion in a cavitating water jet

~~00002RKRSr= (6) If 0tKt=, Eqs. (2),(3) and (4) change into the following equation that is applied to simulations using the MathCAD software. ddd(,,)dd1dxyygxyzzttt=== (7) where 11251(,,)()(1)gxyzABCyxaaaa=++-+, 2132131145678222124531678831(1),23(1)[(1sin],[3cos()] AyyByxxyxzCxyxyxyxzggaaaaaaaaaaaaagaaaa-------=--=++---+=+-- (8) 5g00pK6g0p…