基于PTT黏弹本构模型的聚合物气辅微共挤成型研究

基于PTT黏弹本构模型,构建了描述棒材包覆双层微共挤黏弹流动行为的三维数值模型,采用Elastic Viscous Split Stress、Evolution等方法实现了有限元数值计算,通过分析传统/气辅微共挤的挤出胀大和熔体的速度、剪切速率和压力分布,探究了聚合物气辅微共挤的成型机理。结果表明,气辅微共挤成型过程中,由于气垫膜层的存在及其润滑作用,可有效消除熔体的二次流动且不存在明显剪切速率和口模压降,使熔体沿挤出方向速度分布均匀。

高密度聚乙烯熔体拉伸流动特性分析

基于PTT(Phan-Thien-Tanner)模型,将温度引入结点破坏率H函数中,构建新的聚合物流体本构方程.应用该方程,分析温度对聚乙烯熔体拉伸流动中拉伸应力和拉伸粘度的影响.结果显示,随着温度的升高,熔体的拉伸应力和拉伸粘度都随之下降.

非等温粘弹流体平板收缩流的数值模拟

基于线性PTT本构模型对非等温粘弹流体4∶1平板收缩流进行了模拟,其中分子松弛时间、聚合物黏度与温度的依赖关系通过WLF公式描述。控制方程采用同位网格有限体积法求解,速度-压力以及速度-应力间的耦合采用动量插值技术处理。文中给出了不同We数下粘弹流体等温和非等温情况下流场和应力场的变化情况,分析了温度对流场和应力场的影响,考察了Pe数、We数以及能量方程中参数k对温度场的影响。

轮胎胎面胶料共挤出过程的数值模拟

以某复合胎面胶料(TWR/FB)的共挤出过程为研究对象,利用Polyflow软件,采用Phan-Thien and Tanner(PTT)本构模型和Navier滑移模型对2种胶料熔体在口模内外的流动进行了三维数值模拟,并将模拟得到的挤出断面和试验挤出断面进行了对比分析。同时分析了牵引速度和预口型板的收敛角对共挤出的影响,结果表明,牵引速度对胶料离开口模后的形状和面积胀大比的影响显著,但对胶料在口模内部的流动状态影响不大;适当地增加预口型板收敛角可以增强胶料在口模内的流动性,提高挤出制品的质量。

Thermal and concentration analysis of Phan-Thien-Tanner fluid flow due to ciliary movement in a peripheral layer

This paper presents the analysis of two-layer cilia induced flow of Phan-Thien-Tanner(PTT) fluid with thermal and concentration effect.The Phan-Thien-Tanner fluid model has been used in the analogy of mucus present in the respiratory tract.The two-layer model approach was used due to the Peri Ciliary liquid Layer(PCL) and Airway Ciliary Layer(ACL) present on the epithelium cell in respiratory tract.The mathematical modelling of two-layer flow problem was simplified using long wavelength and small Reynold ’ s number approximation.The resulting differential equation with moving boundary gives exact solution for velocity,temperature and concentration profiles in two layers.The change in pressure has calculated by the results of velocity profile,also the pressure rise was evaluated by the numerical integration of pressure gradient along the channel wall.The impact of physical parameters on pressure rise,velocity,temperature and concentration profile was explained by the graphs.It can be seen from graphs that velocity and temperature profile are maximum in the inner layer of fluid(PCL) and concentration profile is maximum at outer layers of fluid(ACL).

一类粘弹性流体的多重网格法及其收敛性分析

将混合有限元方法与多重网格方法相结合,针对PTT粘弹流体流动问题用v循环多层网格算法对其进行求解,并讨论其收敛性.

Mathematical analysis of Phan-Thien-Tanner fluid model for blood in arteries

In the present paper, we have studied the blood flow through tapered artery with a stenosis. The non-Newtonian nature of blood in small arteries is analyzed mathematically by considering the blood as Phan-Thien-Tanner fluid. The representation for the blood flow is through an axially non-symmetrical but radially symmetric stenosis. Symmetry of the distribution of the wall shearing stress and resistive impedance and their growth with the developing stenosis is another important feature of our analysis. Exact solutions have been evaluated for velocity, resistance impedance, wall shear stress and shearing stress at the stenosis throat. The graphical results of different type of tapered arteries （i.e. converging tapering, diverging tapering, non-tapered artery） have been examined for different narameters of interest.