Research Initiation: Stability Analysis of Interfaces in Coextrusion Flows

研究的目的是确定稳定性 构型内多层流动特性 与共挤出工艺相关。 主要的兴趣是 研究非平行通道壁对两个 不稳定的机制： 流体-流体界面的存在和相关机制 有坚固的墙壁。 基线几何形状为 研究的是由两个常数组成的二维通道 宽度部分由会聚部分连接。 的稳定性 三层牛顿流体稳态等温流动 不同的粘度和密度将使用当地的 线性分析、全局线性分析和直接数值分析 仿真 直接数值模拟将基于时间- 光谱离散化的精确积分（光谱 元素）全非定常Navier-Stokes方程。 本研究将 扩展到非牛顿流体，并将热 方面的影响. 该项目的长期目标是开发 一种可靠的方法（1）预测稳定性 共挤出工艺的特性和（2）设计测试， 和共挤模头的分析。 该研究将导致改进的制造工艺， 聚合物的共挤出。

The objective of the research is to determine the stability characteristics of multi-layer internal flows in configurations relevant to coextrusion processes. The primary interest is to study the effect of non-parallel channel walls on the two mechanisms for instability: the mechanism associated with the presence of fluid-fluid interfaces and the mechanism associated with the presence of solid walls. The baseline geometry to be studied is a two-dimensional channel consisting of two constant width sections joined by a converging section. The stability of steady isothermal flow of three layers of Newtonian fluids of different viscosities and densities will be examined using local linear analysis, global linear analysis, and direct numerical simulation. The direct numerical simulation will be based on time- accurate integration of the spectrally discretized (spectral elements) full unsteady Navier-Stokes equation. The study will be extended to non-Newtonian fluids and will incorporate thermal effects. The long term goal of the project is the development of a reliable method for the (1) prediction of stability characteristics of coextrusion processes and (2) design testing, and analysis of coextrusion dies. The research will lead to improved manufacturing process for coextrusion of polymers.