非等温黏弹流体圆柱绕流的数值模拟(英文)

A collocated finite volume method on unstructured meshes is introduced to simulate the viscoelastic flow of the polymer melt with viscous dissipation past a confined cylinder. The constitutive equation for the simulations is non-isothermal FENE-P model, which is derived from the molecular theories. The temperature effect on the macroscopic fields (e.g., velocity, stress) and microscopic fields (e.g., molecular orientation, deformation, stretch) is investigated by comparison of isothermal and non-isothermal situations. This investigation indicates that temperature rise caused by viscous dissipation should not be neglected since it has significant effect on the macroscopic and microscopic properties of the polymer melt.     

基于ERT传感器和数据挖掘技术的空气水两相流空隙率测量(英文)

Based on an electrical resistance tomography(ERT) sensor and the data mining technology,a new voidage measurement method is proposed for air-water two-phase flow.The data mining technology used in this work is a least squares support vector machine(LS-SVM) algorithm together with the feature extraction method,and three feature extraction methods are tested:principal component analysis(PCA),partial least squares(PLS) and independent component analysis(ICA).In the practical voidage measurement process,the flow pattern is firstly identified directly from the conductance values obtained by the ERT sensor.Then,the appropriate voidage measurement model is selected according to the flow pattern identification result.Finally,the voidage is calculated.Experimental results show that the proposed method can measure the voidage effectively,and the measurement accuracy and speed are satisfactory.Compared with the conventional voidage measurement methods based on ERT,the proposed method doesn’t need any image reconstruction process,so it has the advantage of good real-time performance.Due to the introduction of flow pattern identification,the influence of flow pattern on the voidage measurement is overcome.Besides,it is demonstrated that the LS-SVM method with PLS feature extraction presents the best measurement performance among the tested methods.     

非牛顿流体中气泡上升及聚并过程中液相侧浓度场的数值模拟(英文)

On the basis of Navier-Stockes equation and convection-diffusion equation, combined with surface ten-sion and penetration models, the equations of moment and mass transfer between bubble and the ambient non-Newtonian liquid were established. The formation of a single bubble from a submersed nozzle of 1.0 mm di-ameter and the mass transfer from an artificially fixed bubble into the ambient liquid were simulated by the volume- of-fluid (VOF) method. Good agreement between simulation results and experimental data confirmed the validity of the numerical method. Furthermore, the concentration distribution around rising bubbles in shear thinning non-Newtonian fluid was simulated. When the process of a single ellipsoidal bubble with the bubble deformation rate below 2.0 rises, the concentration distribution is a single-tail in the bubble’s wake, but it is fractal when the bubble deformation rate is greater than 2.0. For the overtaking of two in-line rising bubbles, the concentration dis-tribution area between two bubbles broadens gradually and then coalescence occurs. The bifurcation of concentra-tion distribution appears in the rear of the resultant bubble.     

垂直同心环空管内上升弹状流向团状流的转换

对垂直同心环形管内上升气液弹状流向团状流的转换进行了一定的研究。根据弹状流及团状流的流动特性 ,并考虑同心环形管的结构特征 ,建立了垂直同心环形管上升气液团状流向环状流转换的新的理论模型。通过文中的实验数据及其他研究者的实验数据对该模型的预测性能进行了检验 ,并与其他研究者的模型进行了比较 ,最后还对环形管结构参数对转换的影响进行了一定的分析。     

三相浅层鼓泡塔颗粒悬浮特性

研究了F383 mm的浅层鼓泡塔内高径比(H/DT)、气体分布器、固体浓度(Cs)对气含率和临界悬浮气速(Ugc)的影响. 结果表明,当H/DT<1.5时,随H/DT增大,气含率增大,而Ugc明显下降;当H/DT>1.5时,气含率减小,Ugc变化不大,优化的H/DT约为1.5. 采用四管管式气体分布器,当环径比(d/DT)为0.4时,Ugc最小. 气含率随Cs增大而减小,Cs超过15%(j)时,Ugc随Cs变化不大. 最后,推导得到Ugc的经验关联式,可为工业反应器提供一定指导.     

气固并流向上流动中颗粒聚集的机理

Two-dimensional unsteady cocurrent upward gas-solid flows in the vertical channel are simulated and the mechanisms of particles accumulation are analyzed according to the simulation results. The gaseous turbulent flow is simulated using the large eddy simulation （LES） method and the solid phase is treated using the Lagrangian approach, and the motion of the gas and particles are coupled. The formation of clusters and the accumulation of particles near the wall in dense gas-solid flows are demonstrated even if the particle-particle collisions were ignored. It is found that a cluster grows up by capturing the particles in the dilute phase due to its lower vertical velocity. By this way the small size clusters can evolve to large-scale clusters. Due to the interaction of gas and particles, the large-scale vortices appear in the channel and the boundary layer separates from the wall, which results in very high particle concentration in the near wall region and a very large-scale cluster formed near the separation point.     

Spatial Evolution of CO2-Contaminated Water Bubble Flows in a Vertical Pipe

Experiments on CO₂-water bubble flows in a vertical pipe were carried out for clean water, an aqueous NaCl solution, and an aqueous NaCl solution with 1-octanol to obtain databases of spatial evolutions of the flows with the impurities. Mass transfer correlations for bubbles in these liquids were implemented into a one-way bubble tracking method. Numerical predictions of the spatial evolution, e.g., transition from a bubbly to a slug flow, depending on the impurities agreed well with the experiments.     

气固并流向上流动中颗粒聚集的机理

1 INTRODUCTION Cocurrent upward gas-solid flows are widely used in industrial situations such as circulating fluid- ized bed, fluid catalytic cracking and pneumatic transport. Due to its industrial relevance, many quan- titative experimental and numerical investigations have been carried out[1―4]. Investigations show that upward gas-solid flow always appears heterogenously structured and the distribution of particles is always non-uniform unless the solid phase is very dense or very dilut…     

倾斜窄矩形通道内弹状流特性的实验研究

以空气和水为工质,应用高速摄影仪,对3.25 mm×43 mm的竖直和倾斜窄矩形通道的弹状流进行了可视化研究。按分液相雷诺数将流动分为层流区(Relo3000)和湍流区(Relo≥3000)。实验结果表明,在层流区,气弹上升速度随倾斜角度的增加而增大;在湍流区,倾斜角度对气弹上升速度的影响不明显。基于湍流区拟合得到的分布参数C0和班可夫系数CA分别为1.151和0.788,与实验数据具有较好的一致性。对于空泡份额Jones-Zuber模型和Ishii模型,在湍流区两者预测结果与实验基本一致,但在层流区,Jones-Zuber模型预测效果较好而Ishii模型偏差较大。     

Testing for Neglected Nonlinearity in Cointegrating Relationships*

Abstract. This article proposes pure significance tests for the absence of nonlinearity in cointegrating relationships. No assumption of the functional form of the nonlinearity is made. It is envisaged that the application of such tests could form the first step towards specifying a nonlinear cointegrating relationship for empirical modelling. The asymptotic and small sample properties of our tests are investigated, where special attention is paid to the role of nuisance parameters and a potential resolution using the bootstrap.     

三相流化床动力学特征的影响因素

利用电导探头测试技术,以不同粒径的玻璃珠颗粒、金精矿、金矿氰化尾渣为固相,空气为气相,不同粘度的液体为液相,对三相流化床中不同测孔的电导率进行测试和计算,系统研究了颗粒粒径(dp)、密度(r)、质量(q)、表观气速(Ug)、液体粘度(ml)等对相含率的影响. 结果表明,dp从0.05 mm增加到0.15 mm,气含率(eg)增加2%~3%,而固含率(es)减小2%~4%;其他条件相同,密度大的颗粒es和eg较小;随q增加,eg降低,es增加,玻璃珠颗粒每增加100 g,eg减小约2.5%,es增加约1.5%;随Ug增大或减小,eg和es亦随之增大或减小;随ml增大或减小,eg和es亦呈增大或减小趋势.     

气液两相垂直管流中弹状流型数学模型

本文对气液两相垂直管流的弹状流型的流动机理进行了分析,建立了数学模型。模型的特点是采用了以弹状气泡速度运动的相对座标系,在弹状气泡周围下落液膜流动、液体段空隙率计算和压降计算等方面部提出了新的观点。在两种管径中用空气-水系统进行了实验以验证模型,与一些其他作者的实验数据和理论模型也进行了比较,结果都表明这个机理模型计算的弹状流型的各种流体力学参数值与实验值吻合良好,也优于其他作者提出的模型。     

倾斜管内低温液弹和Taylor汽泡的长度分布

An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in an inclined tube with closed bottom by using a high speed motion analyzer.The experimental tube is 0.018 m ID and 1.0 m in length.The range of the inclination angle is 45°-90° from the horizontal.The experiment focused on the effect of the inclination angle show that the mean liquid slug length and Taylor bubble length increase with the increasing x/D at various inclination angles.At the same x/D,the mean liquid slug length and Taylor bubble length increase first,and then decrease with decreasing inclination angles,with the maximum at 60°.In the vertical tube,standard deviation of the nitrogen Taylor bubble length increase with the increasing x/D.For the inclined tube,standard deviation of the nitrogen Taylor bubble length increases first,and then decreases with the increasing x/D.Standard deviation of the liquid slug length increases with increasing x/D for all inclination angles.