On the Limit of Linear Viscoelastic Response in the Flow Between Eccentric Rotating Disks

The dependence vn frequency of the limiting value of strain, QL, for which linear viscoelastic response occurs in eccentric rotating disks (ERD) flow is studied theoretically and experimentally. The theoretical investigations are based upon the general simple-fluid theory of Coleman and Noll. It is shown that according to this theory +L becomes independent of angular velocity, w, at relatively high frequencies, whereas $L becomes inversely proportional to w at sufficiently low frequencies. The results of previous investigations, based upon some special rheological models, are discussed. The behavior predicted by the simple-fluid theory is confirmed by experiments on polyisobutylene solutions.