Introduction to Rheology. Part 1 Introduction to the Rheology of Complex Fluids. Rheology. Study of deformation and flow of matter A fluid is a substance that deforms continuously under the action of a shearing force. Intuitively, a fluid flows!
Introduction to the Rheology of Complex Fluids
Newton (-Stokes) Law
Deformation rate is expected to be proportional to stress and the constant coefficient of proportionality is called viscosity.
The study of simpler fluids have their own well-defined field, called fluid mechanics.
Purely viscous fluid.
Newton and Simple Fluids
*Faith Morrison, “The News and Information Publication of The Society of Rheology”, Vol 73(1) Jan 2004, pp 8-10
What happens inside a point?
Does Newtonian fluids suffer structural changes?
Rheological studies give background for formulation of boundary problems in dynamics of liquids (governing equations and their solutions) to find numerical values of macro properties.
Analysis of flow problems.
most commonly sought rheological quantity
Increasing shear rate
** Khaldoun, A., E. Eiser, G.H. Wegdam and D. Bonn, “Rheology: Liquefaction of Quicksand Under Stress”, Nature 437 pp 635 (2005)
a – affects the shape of the transition region
l – time constant determines where it changes from constant to power law
n – describes the slope of the power law
h0, h∞ - describe plateau viscosities
ty = yield stress, always positive
m0 = viscosity at higher shear rates