POLYFLOW - Generalised Newtonian fluid model with increasing elongational viscosity?
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The literature reports the existence of generalised Newtonian fluid models where the viscosity law exhibits some level of strain hardening. Is this available in POLYFLOW, and how? Via the mechanism of UDF, it is possible to define such laws in POLYDATA. Among the various possibilities, three laws can be considered, and are given by the equaitons hereafter. 1. Combination of shear thinning and strain hardening: The law can be written as in extensional_viscosity_law_31.gif; a typical UDF is given in visco31.udf.gz 2. Constant shear viscosity and strain hardening: The law can be written as in extensional_viscosity_law_32.gif; a typical UDF is given in visco32.udf.gz 3. Shear thinning and constant elongation viscosity: The law can be written as in extensional_viscosity_law_33.gif; a typical UDF is given in visco33.udf.gz Remarks. In all cases, these laws should be used with the keyword FULLEVALUDF in the .p3rc file for the POLYFLOW calculation. Appropriate evolution(s) should be invoked; they cannot be defined on the parameters of the present viscosity laws. Inflow boundary conditions should be selected with the option "constant normal force". Some references: B. Debbaut and M.J. Crochet, Extensional effects in complex flows, J. non-Newtonian Fluid Mech., 30 (1988) 169-184 B. Debbaut, On the inertial and extensional effects on the corner and lip vortices in a circular 4:1 abrupt contraction, J. non-Newtonian Fluid Mech., 37 (1990) 281-296 C.W. Macosko, Rheology: principles, measurements and applications, Wiley (1994), p.91 |
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