Effect of yield stress on flow rates in one-dimensional shear flows of nonlinear viscous media

The flows of incompressible media with tensor-linear defining relations, including an arbitrary scalar nonlinearity in the form of a monotonically increasing hardening function. There are two types of media: without yield strength (nonlinear-viscous liquids) and with a yield strength (viscoplastic bodies), and the media of the second type are interpreted as finite perturbations of the corresponding media the first type. On the example of the problem of one-dimensional stationary shear flow in round pipe shows the influence of the method of perturbing the limit fluidity at maximum speed and flow. The values of these quantities depend on the sign of the second derivative of the hardening function, i.e. on what material the unperturbed medium is: pseudoplastic or hardening.