Towards viscous debris flow simulation using DualSPHysics v5.2: internal behaviour of viscous flows and mixtures

Abstract. This paper investigates the accuracy of a solid–fluid model using the smoothed-particle hydrodynamics (SPH) software DualSPHysics v5.2 coupled with ProjectChrono for viscous debris flow modelling. It focuses on different validation steps of the method, both for pure fluid and a mixture of fluid and boulders, to build the reliability of the model in order to prepare for the simulation of a simplified debris flow. First, velocity profiles, the free-surface shape and the velocity of surges of a viscous fluid are validated against well-documented experimental data. This is, to the best of our knowledge, one of the few validations of the SPH approach for very viscous flows near the creeping threshold (Re ≈ 1). Second, the influence on the macroscopic viscosity of the introduction of granular elements in a viscous fluid is studied against a semiempirical formula. Finally, the method is applied to simplified 2D debris flow surges with field-like features. Surges modelled in this paper are composed of a viscous Newtonian fluid and polydisperse boulders. The flow of surges of different concentrations is studied, and Froude numbers of real field measurements are retrieved. Such complex models are shown to be relevant to the study of debris flow dynamics.