挤出胀大流动的有限元方法研究(Ⅱ) Maxwell流体和流线有限元

本文对Luo-Tanner提出的流线有限元做了重要的改进,使更适应于微分型本构方程的计算。将原方法沿单元边界积分本构方程改为沿通过单元高斯点的流线的积分。这样回避了速度梯度间断的困难,缓和了出口处应力奇性引起的矛盾,同时又减少了计算量。对比计算表阴,用压力不连续单元来加强不可压缩性限制可以使解的质量和收敛性得到显著的提高。对Maxwell流体轴对称挤出胀大流动的计算获得Weissenberg数高达1.2的收敛解。     

高动压激波管中的真实气体效应

本文用BWR、M-H,R-K等状态方程和精确的量热关系,计算了在高动压激波管中使用SF_6、CO_2做被驱动气体时的真实气体效应。计算所得的反射激波后的压力P_5明显高于按理想气体所计算的压力。H_2驱动CO_2的实验结果与计算值符合得很好。据此,作者提出了充分利用气体的非完全性来获得高压力增益的新途径。论证了合理选择状态方程的重要性。实验表明H_2驱动CO_2的方案完全适用于高动压的标定。     

中等时间尺度下弹道明胶的线性黏弹性模型EI北大核心CSCD

在不同时间尺度下,明胶表现出不同的黏弹性行为。应用蠕变和应力松弛模式研究质量分数为10%的弹道明胶在中等时间尺度下的线性黏弹性行为。低剪切速率下的连续加载-卸载实验显示,在常规感知的时间尺度下(～1min)弹道明胶接近完全弹性体,其线性区应变范围为0～0.25。对蠕变实验对应的中等时间尺度(>1h),选择样品老化24h作为实验起点,这时明胶结构缓慢老化带来的影响可以忽略,从而能够构建恒定参数的本构方程来描述弹道明胶的线性黏弹性行为。对1组蠕变实验结果进行分析,可确定Burgers模型的4个粘弹性参数,然后使用该组参数的模型预测另外2组蠕变实验以及应力松弛实验。结果表明Burgers模型能较好地表征弹道明胶在中等时间尺度下的线性黏弹性行为。     

空气在二甲基硅油和液压油中扩散系数的测量

A piston-cylinder apparatus was established to measure the solubility and diffusivity of air in dimethyl silicone oils and in hydraulic oils based on the PVT state equation of air and the solution of unsteady one-dimensional diffusion equation. The measured diffusivity-temperature relation can be well fitted by the Arrhenius equation for engineering applications. The correlation between the solute diffusivity D and solvent viscosity μ is examined. In terms of Eyring's activation theory, the activation in the air-silicone-oil diffusion process is quite different from that in the momentum transport of the silicone oil: the activation entropy of the former is positive while that of latter is negative. However, the activation enthalpies of the two processes are in the same order of magnitude, which leads to the observation that Dμ/T is roughly constant.     

聚合物溶液哑铃分子模型的数值研究

本文描述用数值方法从分子模型出发计算聚合物溶液的流变性质,并对几种哑铃式分子模型作了计算,解决了若干理论方法无法正确解答的问题     

Effects of groove on behavior of flow between hydro-viscous drive plates

The flow between a grooved and a flat plate was presented to investigate the effects of groove on the behavior of hydro-viscous drive. The flow was solved by using computational fluid dynamics (CFD) code, Fluent. Parameters related to the flow, such as velocity, pressure, temperature, axial force and viscous torque, are obtained. The results show that pressure at the upstream notch is negative, pressure at the downstream notch is positive and pressure along the film thickness is almost the same. Dynamic pressure peak decreases as groove depth or groove number increases, but increases as output rotary speed increases. Consequently, the groove depth is suggested to be around 0.4 mm. Both the groove itself and groove parameters (i.e. groove depth, groove number) have little effect on the flow temperature. Circumferential pressure gradient induced by the groove weakens the viscous torque on the grooved plate (driven plate) greatly. It has little change as the groove depth increases. However, it decreases dramatically as the groove number increases. The experiment results show that the trend of experimental temperature and pressure are the same with numerical results. And the output rotary speed also has relationship with input flow rate and flow temperature.     

NUMERICAL INVESTIGATION OF DUMBBELL MOLECULAR MODELS FOR POLYMERIC SOLUTIONS

A numerical method for calculating the rheological behavior of polymeric liquids from their molecularmodels is presented,and several dumbbell models are then calculated in terms of this method.Answers aregiven to some problems which could not be solved theoretically.     

一种新型Couette流变仪的力矩修正和粘度测量误差分析

为准确计算得出新型Couette流变仪工作段剪切力矩,通过对计算机采集的电机输出转矩进行校核,得出了电机输出转矩真实值;利用商业旋转流变仪测量,得出了实验流体标准大气压下的粘温关系,最后得出了修正力矩与雷诺数的关系。考虑到该流变仪在制造和数据采集中存在误差,利用误差传递计算方法得出了新型Couette流变仪在测量流体粘度时的误差范围。分析结果为进一步测量不同状态下流体的粘度和研究空化奠定了基础。     

聚合物流动分子水平的数值模拟

提出一种新的聚合物流动分子水平的模拟方法,即将流线有限元与分子模型的Brown动力学模拟相结合,求解聚合物复杂流动问题。编写了相应的计算程序,成功地对平行平板间的绕圆柱流进行了模拟。研究的流体介质为Oldroyd-B流体,该流体对应虎克哑铃分子模型的牛顿溶剂稀溶液。通过和采用本构方程的计算结果对比,对这一新方法进行了评价。     

用流动可视化技术研究混合器内研究简报流场及混合效果

引　言不同流体的混合是化工、生物制品、食品工业等工艺过程中一道重要的工序 ,仅依靠流体在输送过程中的自然湍流扩散不能进行有效的混合 ,因此必须使用混合器 ,使液体在短时间内获得均匀的特性 ,达到满意的混合效果 ,并使损失的能量较小 .不同行业由于介质性能和混合要求不同 ,相应混合器的结构也不同 .通常国内外多采用经验类比法设计混合器 ,用取样分析法检验混合效果 .随着新技术的发展 ,深入研究流体混合机理对于高效节能混合器的设计具有重要意义 .尽管许多学者采用数值方法对混合器内部的流动和混合效果进行了研究[1,2 ],但由于数…