Critical Assessment of Capillary and Slit Rheometry

Using finite element analysis (FEA), Tuna and Finlayson (1984) determined the following relationship between Exit and Afj for a sht die  

Using FEA, Vlachopoulos and Mitsoulis (1985) also calculated Exit and Aj for steady-state shear flow of a viscoelastic PS in a slit die. They employed the Carreau model (see Eq. (6.11)) for shear-rate dependent viscosity and the following empirical 

The exit pressure method assumes that flow is fully developed at the exit plane or that the extent of flow disturbances at the exit plane is negligibly small for all intents and purposes. The subject of flow disturbances near the exit plane of a die has been 

R rinted from Vlachopoulos and Mitsoulis, Journal of Polymer Engineering 5(2) 173. Copyright 1985, with permission from Freund Publishing House. 

It was shown, via FEA, that for a Weissenberg number of 0.6, which corresponded to K = 0.4 s i, a velocity rearrangement occurred as the fluid approached the die exit, but the velocity profiles remained more fully developed as the value of increased (Tuna and Finlayson 1984). In that study, was defined by iV g = Xy, with X being a characteristic time of the fluid. Apparently, due to numerical instabilities 

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