The dam-break flow involving non-Newtonian fluids is a type of flow commonly observed in nature as well as in common industrial processes. Experiments of non-Newtonian dam-break flows were conducted in horizontal channels and aqueous solutions of Carbopol 940 were used, which were modeled by the Herschel-Bulkley constitutive equation. Their flows were filmed and the frames were compared with numerical simulations. Two particular results were analyzed: the front wave evolution with time and its stop distance. The CFX software was employed and the simulations were conducted with the VOF method. Both results, numerical and experimental, were compared with shallow water approximation solutions found in literature. The numerical code, which uses complete momentum equations, showed better agreement with the experiments than those using shallow water equations. It seems that the hypotheses used by the shallow water approximated equations are not appropriate for the first instants of the flow, just after the dam-break and errors are introduced. Probably, these errors are propagated producing the differences encountered

This paper describes the physical and rheological property mixtures of water and kaolinitic clay that form the interstitial fluid found in muds from inundations or torrential lava. Several compositions with varying volume concentrations (C nu) were tested in a high-precision R/S rheometer (shear rate x shear stress). The rheometric parameters such as critical stress, apparent viscosity and outflow curves were established. A detailed analysis of the possible thixotropic fluid (shear thinning) and preparation of the mixtures were carried out. Such mud-type mixtures were well adjusted to the Herschel-Bulkley rheologic model at 03 parameters namely tau = tau = tau(c) + K gamma(n), where tau is the shear stress; tau c the yield stress (or initial rigidity); k is the consistency term; n the flow index; and (gamma) over dot = du/dy the deformation rate or shear rates. Considering that this is a thorough research that seeks to infer laws of friction on a canal taking into account the non-Newtonian rheology of the flowing material, it is observed that the tested mixtures specifically keep away from the Newton model, though less for the Bingham model, and adjusted well to the Herschel- Bulkley model, especially for lower deformation rates. Finally, from a refined literature review on the subject, it was appropriate to describe in detail a wider range of deformation rates and overall behavior laws of the various parameters of the Herschel Bulkley as a function of the concentration by volume (C nu)

An experimental approach to examine the instabilities present on free surfaces of non-Newtonian fluid flow occurring in inclined channels is presented. When these flows occur in favorable conditions of inclination and discharge, it is observed that the propagation of instabilities can evolve into a specific type of wave, known as roll waves. The experimental apparatus developed allows simulation of stabilized roll waves in many scenarios for Newtonian and non-Newtonian rheology fluids, thereby constituting a highly useful approach for the understanding and control of roll waves. The fluid test for the non-Newtonian case used a gel rheometrically representative of the muddy material presented in natural disasters, such as mudflows. A low-cost, high-performance, and nonintrusive level measurement system (ultrasonic transducer) is proposed. A comparison between the experimental results obtained and a one-dimensional (1D) mathematical model exhibited good amplitude and wave-period estimations.