Abstract
Although the flow behaviour of non—Newtonian fluids in channels of constant cross—section is well understood, and there are established models to describe it, the same is not yet true of flow in convergences where the extensional strain rate becomes significant compared to the wall shearrate. Various methods of describing the convergent flow behaviour of polymeric liquids in dies and in other regimes have formed the basis of recent reviews1–3 (see also Chapter 8).
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Abbreviations
- Subscripts 0 and 1:
-
refer to die entry and exit respectively.
- R :
-
radial distance in cylindrical coordinates; die or capillary radius
- x :
-
axial distance from die cone apex
- L :
-
capillary length
- r, θ, ϕ :
-
spherical coordinates, based on die cone apex
- α :
-
die semi-angle; α, value for minimum pressure
- a :
-
surface area of spherical shell
- b :
-
radius of spherical shell in exit region
- V :
-
volume of truncated spherical exit region
- β :
-
angle subtended at axis by die exit at distance b
- Re :
-
Reynolds number
- ρ :
-
density
- v :
-
velocity; v r, r-direction component; ῡ, mean value
- σ :
-
elongating stress
- τ :
-
shear stress
- ε :
-
elongational strain rate
- γ :
-
shear strain rate; γA, apparent wall shear rate at the die exit or in the capillary
- A, n :
-
extensional power law constants
- B, m :
-
shear power law constants
- λ :
-
extensional viscosity or anisotropic extensional viscosity; λA, apparent (n = 1) value. Subscripts ‖ and ┴ refer to directions parallel and perpendicular to anisotropic reference direction. λRes refers to resin phase only
- η :
-
shear viscosity or anisotropic shear viscosity; ηRes resin phase shear viscosity; ηA apparent (m = 1) shear viscosity
- a ij :
-
coefficients in the reciprocal viscosity tensor
- P :
-
reservoir hydrostatic pressure
- P Ent, P Cap :
-
contributions of entry flow and capillary flow towards total pressure
- PSEnt, PEEnt :
-
contributions of shear dissipation and extensional dissipation towards PEnt
- P’ Ent :
-
contribution of exit transition region
- Ṗ Ent :
-
minimum value
- P*:
-
dimensionless pressure
- p :
-
hydrostatic pressure
- Q :
-
volume flow rate
- V f, l, d :
-
volume fraction; length and diameter of reinforcement
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© 1993 Springer Science+Business Media Dordrecht
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Gibson, A.G. (1993). Converging Dies. In: Collyer, A.A., Clegg, D.W. (eds) Rheological Measurement. Springer, Dordrecht. https://doi.org/10.1007/978-94-017-2898-0_3
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