Rr. Huilgol, VARIATIONAL PRINCIPLE AND VARIATIONAL INEQUALITY FOR A YIELD STRESS FLUID IN THE PRESENCE OF SLIP, Journal of non-Newtonian fluid mechanics, 75(2-3), 1998, pp. 231-251
Minimum and maximum principles. which have been derived for the creepi
ng flows of a yield stress fluid, are extended to flows when wall slip
is present. In addition, the minimum principle is shown to lead to a
variational inequality when wall slip is absent, and the latter is gen
eralised to include inertial effects in specific cases, including hows
in pipes and the how past a body at rest due to a uniform flow at inf
inity. Moreover, the variational inequality is extended to deal with p
roblems when wall slip may be present. Finally, the squeezing flow bet
ween two co-axial and parallel disks is re-examined as an application
of the variational principles obtained here. (C) 1998 Elsevier Science
B.V. All rights reserved.