拉桥朗日—欧拉方法模拟高分子复杂流体平面收缩流动

为验证拉格朗日－欧拉方法的准确性,对高分子溶液的４：１平面刷缩流动问题进行了数值模拟,采用单松驰时间的Ｐｈａｎ Ｔｈｉｅｎ－Ｔａｎｎｅｒ本构方程,得到ＰＩＢ／Ｃ１４溶液在Ｄｅ＝３．０的收缩流动的计算结果,同Ｑｕｉｎｚａｎｉ等所做的收缩流动实验中的稳态流场物理量结果进行了比较,在定量上取得较好的一致性。证明拉格朗日－欧拉方法能够在定性上乃至在定量上准确地预报高分子复杂流体的流动行为,在描述真实的物理     

拉格朗日-欧拉方法模拟高分子复杂流体平面绕流

为验证拉格朗日 欧拉方法的准确性 ,对高分子溶液的 2∶1绕圆柱流动问题进行了数值模拟 ,采用单松弛时间的PhanThien Tanner本构方程 ,得到PIB/C14溶液在De =0 93的绕流计算结果 ,同Baaijens等所做的绕流实验中的稳态流场物理量的测量结果进行了比较 ,在定量上取得较好的一致性 .证明拉格朗日 欧拉方法能够在定性上乃至在定量上准确地预报高分子复杂流体的流动行为 ,在描述真实的物理过程时是合理、准确的     

拉格朗日欧拉计算机模拟方法——对牛顿流体的解

用拉格朗日 欧拉方法模拟计算了各种流场中牛顿流体的流动问题 ,并以此来验证该算法的正确性 .其中 ,对具有准确解的二维Poiseuille流动、Couette流动以及同心圆筒间的流动 ,将模拟得到的数值解与数学解析解直接加以比较 ;对没有准确解的绕圆柱的平面流动、平面收缩和扩张流动 ,将模拟结果同一些已经发表的模拟或实验结果相比较 .从文中可见 ,该方法得到的各种结果都是合理、准确的 .     

聚合物复杂流体流动的动力学模拟

介绍聚合物复杂流体流动问题的模拟方法。通过比较,指出了经曲有限元方法的局限性和拉格朗日－欧拉方法在模拟复杂流动问题上的优越性。拉格朗日－欧拉方法的模拟结果同聚合物流体复杂流动的实验结果相一致,表明该方法在对复杂流体的动力学行为的模拟 合理的和可行的。     

第9届流动分析国际会议

19届流动(注射)分析国际会议于2003年2月18日至21日在澳大利亚Geelong市召开,由Deakin大学主办,大会报告共4个。(1)巴西Sa彲Ｐａｕｌｏ大学Ｉ.Gutz,流动分析中的电化学———远远超出检测器的范围之外;(2)联合王国Hull大学G.Green way,芯片上的实验室 收缩型流动分析;(3)美国全球流动注射分析中S.G.Marshall,区带流体学;(4)报告人未详(待考),固相反应器与液相发射器。特邀报告共7个。(1)瑞士Basel大学P.Haus er,流动分析用的电化学传感检测;(2)澳大利亚Melbourne大学S.Kolev,在气相扩散和全蒸发流动注射分析中的金属形态的分离;(…     

离子色谱法测定啤酒及其酿造水中的无机阴离子

 采用阴离子分离柱YSA880 2 2A 9( 2 5 0mm× 4mmi.d .)分离 ,电渗析抑制器和电导检测器检测 ,以 2 4mmol/LNa2 CO3 3mmol/LNaHCO3(体积比为 2∶1)为流动相 ,以保留时间和标样添加法定性 ,标准曲线法定量 ,测定了啤酒及其酿造水中的无机阴离子。方法操作简便、快速 ,结果准确、可靠。     

反相高效液相法测定四环素类抗生素

 利用高效液相法 ,在C18柱上以甲醇 乙腈 0 0 1mol/L草酸溶液 (pH 2 0 ) (体积比为 11∶2 2∶6 7)为流动相 ,采用 2 6 7nm紫外光进行检测 ,在 2 2min内将 7种四环素类抗生素全部洗脱并达到基线分离。探讨了流动相的pH值、草酸的浓度、流动相中有机相的比例以及检测波长等因素对分离度和灵敏度的影响。采用标准加入法定量 ,对两种实际样品进行了分析。结果表明 :该方法操作简单、灵敏度高、定量准确。     

反相高效液相色谱法测定五肽胃泌素及其酶促降解产物

在反相ODS柱上,用NH_4Ac-HAc缓冲溶液和甲醇作流动相进行梯度洗脱,清晰地分离了五肽胃泌素及其酶促降解产物。HPLC法分离简便,定量准确,可有效地用于研究活性多肽的酶促降解机制。通过HPLC法探讨五肽胃泌素的降解过程尚属首次。     

反相高效液相色谱法测定产琥珀酸放线杆菌发酵液中的有机酸

提出了一种利用高效液相色谱法分析产琥珀酸放线杆菌发酵液中有机酸的方法。在EclipseXDB C8(4 .6mmi.d .× 1 5 0mm ,5 μm)色谱柱上 ,以 0 .0 0 5mol L硫酸溶液 (pH 2 .5 )作流动相 ,流速为 1mL min ,紫外检测波长 2 1 0nm。 7min内可以把 6种混合酸标样完全分离定量。发酵液经离心后直接进样分离定量 ,其中的琥珀酸、乳酸的回收率大于 97%。经多次实验结果证明 :本方法是测定琥珀酸发酵液中各有机酸的快速、有效的定量测定方法。     

反相高效液相色谱法测定牛奶中的主要蛋白质

建立了测定牛奶中的主要蛋白质的反相高效液相色谱法,对前处理方法进行了优化,采用Agilent Zorbax 300SB-C8(250 mm×4.6 mm,5 μm)色谱柱,三氟乙酸-水-乙腈流动相梯度洗脱,214 nm检测,柱温45 ℃,外标法定量.测定κ-CN, αs2-CN, αs1-CN, β-CN, Whey和Igg的线性关系良好,相关系数均大于0 999,加标回收率在74.8%～132.5%之间.大豆蛋白质不影响分离与检测.采用本方法分析了9种牛奶样品中上述蛋白质的含量与总量,结果表明,本方法测定结果准确可靠.不同样品中4种酪蛋白与乳清蛋白的比例基本接近,但是不同品牌之间存在一定差异.     

示波极谱图的伸缩及位移

利用示波极谱图的伸缩或位移指示滴定终点是示波极谱滴定的一种新技术.本文全面探讨了示波极谱图伸缩及位移的原理,并用实验作了对照,理论计算与实验结果一致.伸缩来源于电极阻抗的变化,位移则主要由动力学因素引起.     

Joule heating and heat transfer in poly(dimethylsiloxane) microfluidic systems

Joule heating is a significant problem in electrokinetically driven microfluidic chips, particularly polymeric systems where low thermal conductivities amplify the difficulty in rejecting this internally generated heat. In this work, a combined experimental (using a microscale thermometry technique) and numerical (using a 3D "whole-chip" finite element model) approach is used to examine Joule heating and heat transfer at a microchannel intersection in poly(dimethylsiloxane)(PDMS), and hybrid PDMS/Glass microfluidic systems. In general the numerical predictions and the experimental results agree quite well (typically within +/- 3 degree C), both showing dramatic temperature gradients at the intersection. At high potential field strengths a nearly five fold increase in the maximum buffer temperature was observed in the PDMS/PDMS chips over the PDMS/Glass systems. The detailed numerical analysis revealed that the vast majority of steady state heat rejection is through lower substrate of the chip, which was significantly impeded in the former case by the lower thermal conductivity PDMS substrate. The observed higher buffer temperature also lead to a number of significant secondary effects including a near doubling of the volume flow rate. Simple guidelines are proposed for improving polymeric chip design and thereby extend the capabilities of these microfluidic systems.     

MODELING THE CHAIN CONFORMATION OF POLYMER MELTS IN CONTRACTION FLOW

A constitutive model of quasi-Newtonian fluid based on the type of flow is used in abrupt planar contraction now.The numerical results from finite element analysis are consistent with experimental data for stress patterns and velocityprofiles in the flow field. The chain conformations of polymer melts are then investigated in such a planar contraction byusing the phenomenological model with internal parameters proposed by the author. That is, the shape and orientation ofpolymer chain coils are predicted and discussed in different flow regions of the contraction flow field that possess simpleshear flow, extensional flow, vortical flow, and mixed flow respectively.     

星形胶束自由能和聚集数的理论分析

ＡＢ型嵌段聚合物在选择性溶剂中将发生微相分离,形成一种球形胶束[1].所谓选择性溶剂是指此溶剂仅能溶解共聚物中某一链段,而对另一链段则为不良溶剂.对这一体系的实验研究是从80年代兴起的,主要采用现代测试技术来表征形成胶束的回转半径[2],动力学半径[3]、聚集数[4]和临界胶束浓度[5].从分子图景上看来,这种球形胶束包括两部分,内核(Ｃｏｒｅ)为密堆砌的链段Ａ;壳层(Ｃｏｒｏｎａ)为溶涨的链段.Ｈｅｌｆａｎｄ等[6]最早利用数值计算法来研究嵌段聚合物在本体中的微相分离的问题;Ｌｅｉｂｌｅｒ等[7]将此方法引入嵌段聚合物/均聚物体系.…     

Numerical simulation of three‐dimensional polymer extrusion flow with differential viscoelastic model

The numerical simulation of viscoelastic flow problems is nowadays an effective way of investigating the complex flow mechanism related to practical engineering problems, such as plastic injection, blow molding and extrusion. The mathematical model of a three‐dimensional (3D) viscoelastic flow in a typical contraction die for polymer extrusion is established and a stable solving method is investigated. The penalty finite element method (FEM) is performed to simulate the viscoelastic melts flow in the channel with a differential constitutive model. The discrete elastic‐viscous split stress (DEVSS) formulation and the streamline‐upwind Petrov–Galerkin (SUPG) technology are employed to improve the computation stability. Both the implementation of the numerical scheme and its application in the practical process analysis are investigated. The effects of various calculation control parameters and different material parameters upon the numerical results are discussed. The 3D flow patterns in the extrusion die with different contraction angles are further investigated based on the above discussions. Copyright © 2007 John Wiley & Sons, Ltd.     

Discrete element simulation of the dynamics of adsorbents in a radial flow reactor used for gas prepurification

Radial flow reactors (RFR) are used in thermal swing adsorption (TSA) processes for gas prepurification. The aim of this work is to show the validity of the discrete element method (DEM) to simulate the effect of thermal expansion and contraction cycles occurring in such processes on the packed bed of RFR reactors. Both mono-layered and bi-layered packed beds of adsorbents are investigated. A DEM-based model of a full-scale size unit was developed, the parameters of which were calibrated by means of particle-scale experimental measurements and simple auxiliary DEM simulations. The DEM-based model used is isothermal and the thermal expansion and contraction phenomena are modelled through the displacement of the inner and outer walls of the computational domain. First, the accuracy of this model is assessed using analytical values of the static wall pressure (i.e. with no wall motion) as well as experimental measurements of the dynamic wall pressure (i.e. with wall motion) of a bi-layered bed. Next, simulation results for a few process cycles in the case of a bi-layered packed bed indicates that little mixing occurs at the interface between the two types of adsorbents. To our knowledge, this is the first time that simulation is used to investigate the behavior of the packed bed of a RFR in a TSA process. The results obtained with the proposed model show that the DEM is a valuable tool for the investigation of such slow dynamical processes, provided a careful calibration is done.     

TRANSIENT EFFECT OF A BOGER FLUID FLOWING AROUND A CONFINED CYLINDER

This paper is concerned with the numerical simulation of the transient effect of an inertialess Boger flow past aconfined circular cylinder and the comparison of predictions with particle image velocimetry (PIV) measurements given byShiang et al., Dynamic simulation based on the Oldroyd-B constitutive model was carried out using a Lagrangian-Eulerianalgorithm. The evolution of velocity field was obtained for the flow at two Deborah (De) numbers, i.e. De = 1.2 and 3.0. Atlow De, the flow reached steady state rapidly, and showed a symmetric flow regime. However, at high De, the time requiredto reach steady flow behind the cylinder increased significantly, and the distribution of the velocity field appears to beasymmetric with respect to the stagnation line. Fairly good agreement between the numerical results and the experimentalobservations is reported. It can be concluded that both the experimental measurements and the present simulations indicatethat the elasticity of the polymeric flow strongly affect the flow regime of viscoelastic flow around a confined cylinder.     

离子型共聚单体用于高固含量无皂乳液聚合的研究——甲基丙烯酸异丁酯/甲基丙烯酸甲酯/丙烯酸丁酯无皂乳液聚合体系

该文采用自行合成的一种带亲水性磺酸离子基团及羟基的可共聚单体 3 烯丙氧基 2 羟基丙磺酸钠(AHPS)用于甲基丙烯酸异丁酯 /甲基丙烯酸甲酯 /丙烯酸丁酯 (IBMA/MMA/BA)无皂乳液聚合体系 .对乳胶粒粒径大小、乳液流体力学行为、共聚物的动态力学性质、拉伸行为及耐水性进行了研究 ,并对乳胶粒的成核机理进行了探讨 .实验结果表明 ,带亲水性离子基团可共聚单体AHPS的加入可获得 0 6μm左右的乳胶粒 ,乳液固含量可达 60 % ,表现粘度测定结果表明乳液呈Bingham流体 .三元共聚物在动态粘弹谱图上只出现单一的玻璃化转变温度峰 ,是完全的无规共聚物 ,拉伸强度明显大于常规乳液聚合方法得到的聚合物 ,耐水性也得到显著提高 .