The Model of Fast Contraction Flows for Polymeric Melts

高浓度聚合物流体中的聚合物扩散不稳定性

The polymer diffusive instability in highly concentrated polymeric fluids

本研究针对聚合物熔体挤出的熔体破裂问题，结合含应力扩散的Oldroyd-B模型分析高浓度流体中聚合物扩散不稳定性（PDI），解析其边界层结构与特征值，关联鲨鱼皮不稳定性，证实惯性会降低PDI存在的最小魏森贝格数。

Quasi-1D Modeling of Polymer Melt Die Swell in Short Dies

This paper describes the isothermal die swell using our recent quasi-1D model for fast (high Deborah number) contraction flows of polymers melts. Because the model analyzes the flow in several flow regions as one continuous process, it makes possible to evaluate the die swell as a qusi-1D extrudate flow in dies of various lengths. Using the asymptotic matching condition for the change in flow type at the die exit allowed us to find the swelling profile for extrudate along the flow direction. The calculations in paper performed using a multi-mode viscoelastic constitutive equation of differenti…

Low Reynolds number pulsatile flow of a viscoelastic fluid through a channel: Effects of fluid rheology and pulsation parameters

As the first endeavour, we have analyzed the pulsatile flow of Oldroyd-B viscoelastic fluid where the combined effects of fluid elasticity and pulsation parameters on the flow characteristics are numerically studied at a low Reynolds number. Computations are performed using a finite-volume based open-source solver OpenFOAM by appending the log-conformation tensor approach to stabilize the numerical solution at high Deborah number. Significant flow velocity enhancement is achieved by increasing the viscoelastic behaviour of the fluid. High-velocity gradient zones and high polymeric stress regio…

Edge-induced shear banding in entangled polymeric fluids

Despite decades of research, the question of whether solutions and melts of highly entangled polymers exhibit shear banding as their steady state response to a steadily imposed shear flow remains controversial. From a theoretical viewpoint, an important unanswered question is whether the underlying constitutive curve of shear stress $σ$ as a function of shear rate $\dotγ$ (for states of homogeneous shear) is monotonic, or has a region of negative slope, $dσ/d\dotγ<0$, which would trigger banding. Attempts to settle the question experimentally via velocimetry of the flow field inside the fluid …