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Experimental study of film thickness and free surface velocity around a rotating roll for non‐newtonian fluids
Author(s) -
Chono S.,
Iemoto Y.,
Tomizawa T.
Publication year - 1993
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760332305
Subject(s) - newtonian fluid , viscoelasticity , materials science , non newtonian fluid , mechanics , generalized newtonian fluid , free surface , shear rate , rheology , optics , composite material , physics
Measurements are performed on film thickness and free surface velocity around a rotating roll for Newtonian, non‐Newtonian inelastic, and viscoelastic fluids by using noncontact methods of a capacitance probe and a laser Doppler velocimeter probe. The film thickness decreases with increasing inspection angle for Newtonian fluids. For non‐Newtonian fluids, it retains an approximately constant value, owing to shear‐thinning of viscosity, except for a meniscus region development, which is dependent on fluid elasticity. Comparison of current results with the film thickness from a previous work is also made. With the increment of inspection angle, the free surface velocity increases rapidly in the meniscus region and maintains a constant value almost equal to a roll speed in the other region for viscoelastic fluids, while it increases linearly for Newtonian fluids. The shear rate at a roll surface is presented assuming that the velocity distribution in the liquid film is a polynomial equation. It is found that viscoelastic fluids exhibit different behavior from that of Newtonian and non‐Newtonian inelastic fluids. Evaluation of the force acting on the liquid film for Newtonian fluids implies that the velocity gradient at a roll surface in an ascending region may be steeper than the parabolic form assumed in this study.