Abstract

Mathematical models of an unsteady turbuent liquid pipe flow, with a quasi-steady distribution of an eddy viscosity in a pipe cross-section taken into account, were described. These models are based on four-region distributions of the eddy viscosity coefficient. They were adapted for determination of the instantaneous friction factor. For the three-region model - in case of low frequencies - dynamic velocity changes as a frunction of frequency. It was shown that the instantaneous friction factor value considerably differs from the quasi-steady one.