'Natural' disasters: analyzing pulsating regimes in mudflows

Abstract

When talking about natural disasters and risks, so present in the Brazilian scenario, this work proposes a mechanicist evaluation for fluid flows in open channels (channels, hills, watershed, spillways, etc.). The roll wave phenomenon, characterized by its periodic configuration and fast wave fronts in the free surface, may occasionally appear in such flows, if sufficient conditions were reached. Its presence may compromise the integrity of nearby structures and may increase the damage these disasters offer. This work evaluates numerically and analytically the generation of such waves in Newtonians and non-Newtonian flows. The main purpose reached by this work was to verify the validity of analytical and numerical methods based on the results given by the numerical simulation. In the numerical plan, finite volumes method was used, by the FLUENT software (with complete equations). In addition, the analytical model used already established for mudflows (viscoplastic fluid) was obtained from the manipulation of the Cauchy equations vertically averaged, with the Herschel-Bulkley rheological model inserted in the viscous part of the tension tensor.A comparative analysis between the methods was developed, resulting in a good agreement.