The Viscoelastic Swirled Flow in the Confusor

Abstract

A two-dimensional mathematical model for a steady viscoelastic laminar flow in a confusor was developed under the condition of swirled flow imposed at the inlet. Low density polyethylene was considered as a working fluid. Its behavior was described by a two-mode Giesekus model. The proposed mathematical model was tested by comparing it with some special cases presented in the literature. Additionally, we propose a system of equations to find the nonlinear parameters of the multimode Giesekus model (mobility factor) based on experimental measurement. The obtained numerical results showed that in a confusor with the contraction rate of 4:1, an increase in the swirl intensity at Wi < 5.1 affects only the circumferential velocity, while the axial and radial velocities remain constant. The distribution pattern of the first normal stress difference in the confusor is qualitatively similar to the one in a channel with abrupt contraction, i.e., as the viscoelastic fluid flows in the confusor, the value of N1 increases and reaches a maximum at the end of the confusor. Dimensionless damping coefficients of swirl are used to estimate the swirl intensity. The results show that the swirl intensity decreases exponentially.

Exact Solution for Viscoelastic Flow in Pipe and Experimental Validation

“…The literature data [20] were used to find th linear spectrum of the relaxation time for the four-modal rheological equations of state o a viscoelastic medium. The search for a set of nonlinear parameters of rheological model ( 3) and ( 4) is based on the flow curve approximation; e.g., for the Giesekus model, a de tailed algorithm was presented in our earlier published work [21]. For the reader's con venience, Table 1 presents Since the specific values of the average bulk velocity (V a ) used in flow visualization were calculated during post-processing by integrating the velocity profile over the pipe section according to the formula…”

Insights into the tiger stripe phenomenon of polypropylene and its blend in injection molding with a rapid heat exchange mold

“…Different from other flow instability phenomena, such as sharkskin 6 and melt fracture 7 observed in extrusion process, the formation of TS is quite complicated in injection molding because of the nonequilibrium and unstable states of polymer. Even though there are a large number of literatures paid attention to the flow instability of polymer melts, [8][9][10][11][12] only limited literatures have reported the TS phenomenon in injection molding. Therefore, it is of great importance and challengeable to uncover the formation mechanism of TS from both the fundamental and application viewpoints.…”