Abstract
Previous studies have argued that rheological equations of the differential type, such as second-order fluid models, are inadequate because they result in unstable solution after cessation of steady shear. If the sign of the viscoelastic coefficient is selected so that the storage modulus is positive, the fluid velocity increases indefinitely and the flow does not decay by viscous dissipation, in contradiction to thermodynamic laws. This study mitigates this problem by demonstrating that the solution of such equations is actually stable at low values of Deborah number De, where these equations are only valid for other reasons. In fact, second order and higher order differential type equations are applicable only if the relaxation time of the fluid is low relative to a characteristic time of the flow. The study shows how to determine the characteristic time and thus clarifies, in practical terms, the limits of the region where differential type equations can be applied.
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References
Coleman BD (1985) Viscoelasticity and rheology. Academic Press 125–155
Coleman BD, Noll W (1960) Arch Rational Mech Anal 6:355–370
Coleman BD, Duffin RJ, Mizel VJ (1965) Arch Rational Mech Anal 19:100–116
Coleman BD, Markovitz H (1964) J Appl Phys 35:1–9
Coleman BD, Markovitz H (1974) J Polymer Science 12:2195–2207
Dunn JE, Fosdick RL (1974) Arch Rat Mech Anal 56:191–252
Dunwoody J, Dunwoody NT (1982) Arch Rational Mech Anal 80:71–98
Harnoy A (1976) Journal of Fluid Mechanics 76:501–517
Harnoy A (1987) Rheol Acta 26:493–498
Harnoy A (1989) Journal of Rheology 33:93–117
Huilgol RR (1968) Int J Non-Linear Mechanics 3:471–482
Huilgol RR (1979) Rheol Acta 18:451–455
Joseph DD (1990) Fluid dynamics of viscoelastic liquids. Springer New York 458–459
Metzner AB, White JL, and Denn MM (1966) AIChE Journal 12:863–866
Noll W (1958) Arch Rational Mech Anal 14:197–226
Rajagopal KR, Fosdick RL (1980) Proc Roy Soc, London Series A, 339:351–377
Reiner M (1964) Physics today 12:62
Sus S (1984) Rheol Acta 23:489
Tichy JA, Modest MF (1980) J Rheol 24:829–845
Ting TW (1963) Arch Rat Mech Anal 14:1
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Harnoy, A. The relation between CDM instability and Deborah number in differential type rheological equations. Rheol Acta 32, 483–489 (1993). https://doi.org/10.1007/BF00396179
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DOI: https://doi.org/10.1007/BF00396179