Non-Newtonian Flow of Structured Systems. XXVIII. Accuracy Estimation of Rheological Equation Coefficients

Abstract
Rheological equations with different number of coefficients were used to describe the non-Newtonian flow of suspensions, polymer solutions, and melts. Determining of the magnitude of three or more coefficients by the nonlinear regression method is an inverse problem and does not allow to obtain exact values of the coefficients. We have proposed a method for estimating the exactness of the coefficients of the rheological equation, namely, the generalized flow equation, in which the method of statistical tests is used. The calculation of the root-mean-square deviations of the coefficient estimation error makes it possible to obtain the absolute and relative errors of the coefficients. Depending on the system studied, the relative measurement errors of the coefficients are in the range from 1 to 17 %, except for the polymer melt. The article presents graphs of flow curves in root coordinates, which demonstrate a good correspondence between experimental and calculated data.

Keywords: non-Newtonian flow, rheological equation, generalized flow equation, estimation of the accuracy of the coefficients of the equation