Studying effect of entrainment on dynamics of debris flows using numerical simulation

• Published in: Computers & geosciences 2020-01, Vol.134, p.104337, Article 104337
• Main Authors: Nikooei, Mohammad, Manzari, Mehrdad T.
• Format: Article
• Language: English
• Subjects: Debris flows; Entrainment; Granular flows; Smoothed particle hydrodynamics (SPH); Viscoplastic model
• ISSN: 0098-3004; 1873-7803
• DOI: 10.1016/j.cageo.2019.104337

This paper studies entrainment phenomenon in debris flows using full flow (non-depth-averaged) equations and an Incompressible Smoothed Particle Hydrodynamics (ISPH) method. A viscoplastic constitutive relationship is adopted for both the overlying fluid and bed material. Collapse of a two-dimensional dry granular column on a horizontal bed consisting of entrainable dry granular material is considered as a benchmark problem. The adopted ISPH method for simulation of collapse over rigid and entrainable beds is validated using available numerical and experimental data. To quantify the effects of entrainment on dynamics of flow, the initial aspect ratio of granular column (a) is varied and the variations in momentum and energy of moving materials are investigated. •Presence of a loose bed material and associated entrainment increases the runout.•Entrainment decreases the maximum velocity of flow independent of aspect ratio a.•Entrainment increases the flowing mass and thus the x-momentum independent of a.•The available energy for the horizontal motion of entraining flows is limited.•Entrainment increases/decreases the destructive force and power, respectively.