Determination of constitutive equations for magnetic fluids by using the theory of integrity bases and the principle of maximal dissipation rate.

Abstract

Constitutive equations for magnetic fluids have been investigated by some researchers. However, these equations cannot describe the phenomena of magnetic fluids perfectly for lack of some elements with which constitutive equations should satisfy, for example, considering viscoelastic effects, satisfying the principle of material frame-indifference, being formulated by using the thermodynamic method. We introduced a new way of determining constitutive equations for magnetic fluids. That is the method which is a combination of the theory of integrity bases and the principle of maximal dissipation rate based on the thermodynamic discussions. Compared with previous ways, this has such merits as follow : all equations satisfy the principle of material frame-indifference and only include the terms which are permitted by thermodynamics : non-Newtonian effects except magnetic effects can be described because of considering nonlinear terms, we can obtain the constitutive equations not only in the case of he compound process but of the complex process as well.