INTEGRAL MODELS OF RHEOLOGICALLY NONSTATIONARY FLUIDS

Consideration has been given to the status and prospects for development of integral models of rheologically nonstationary (viscoelastic) fl uids. The predominant fi eld of application of these models are media with a fairly long relaxation time (concentrated polymer solutions and melts, biological tissues, foams, and others), for which taking account of the preceding states assumes substantial importance. The emphasis has been placed on today′s integral models developed on the basis of a classical Kaye–Bernstein–Kearsely–Zapas model through singling out viscous and purely elastic components in the potential function of the medium′s stored energy (so-called factorization of the K-BKZ model). An analysis has been made of the thixotropy and rheopexy phenomena caused by the lag of the reaction of response of rheologically nonstationary fl uids to external action. The authors have shown the expediency of the loop test used in determining the integral parameters of motion of viscoelastic fl uids (velocity, fl ow rate, pressure difference, etc.), and also the possibility of using a fl ow curve representing the averaging of the ascending and descending branches of a hysteresis loop in the case of its small width.
   
Author:  O. M. Sokovnin, N. V. Zagoskina, and S. N. Zagoskin
Keywords:  mathematical models, viscoelastic fl uids, thixotropy, rheopexy
Page:  542