TECHNICAL NOTE Preliminary Discrete Particle Model in a Computer Simulation of Cohesive Debris Flows Fabio V. De Blasio Received: 17 September 2010 / Accepted: 15 October 2011 / Published online: 17 November 2011 Ó Springer Science+Business Media B.V. 2011 Abstract The paper presents a numerical method to simulate the dynamics of a cohesive debris flow. The model is based on a molecular dynamics algorithm where the equation of motion is calculated for an ensemble of interacting particles. In addition to the hard-core repulsion and to the other forces commonly introduced to simulate granular media, in this work an attractive force between particles is added as a model for cohesion. The model is computationally straight- forward and devoid of a series of cumbersome problems affecting fluid mechanical codes. Prelimin- ary simulations presented here look promising, and indicate directions of study for a better comparison and test against field data. Keywords Debris flow  Molecular dynamics  Cohesion 1 Introduction The interest in physical understanding of debris flows has considerably increased during the last decades (Iverson 1997; Lorenzini and Mazza 2004), raising the need for more reliable numerical simulations of cohesive debris flows, mudflows, and hyperconcen- trated flows. Cohesive flows are frequently modelled by solving iteratively the dynamical momentum equa- tions coupled with a rheological equation for the non- Newtonian fluid. In this framework, the equations are solved in a Eulerian or Lagrangian grid; the dynamics is then built on a finite element, finite difference, or finite volume algorithm, or on depth-integrated finite difference model (see e.g. Chen and Lee 2000; Imran et al. 2001; Gauer et al. 2006 and works cited therein). Calculations are usually carried out by use of com- mercial computer solvers or freeware software. There are, however, a number of drawbacks in a fully fluid- dynamical approach that justify parallel investigations with alternative computational techniques. Firstly, it may be restrictive to envision a debris flow as a liquid substance, as it exhibits plastic characteristics intermediate between a solid and a liquid. Deposits have often stable walls and rest with high angle of repose. A second limitation concerns the behaviour of the debris flow in contact with the ground. The no-slip condition is usually imposed at the ground, which contrasts with the behaviour of debris flows in the natural environment, where the material often slips when flowing on previous deposits or on F. V. De Blasio PHYFES, Oslo, Norway F. V. De Blasio Dipartimento di Scienze Geologiche e Geotecnologie, University of Milan ‘‘Bicocca’’, Milan, Italy F. V. De Blasio (&) Department of Geosciences, University of Oslo, Blindern, P.O. Box 1047, 0316 Oslo, Norway e-mail: fvblasio@geologi.uio.no 123 Geotech Geol Eng (2012) 30:269–276 DOI 10.1007/s10706-011-9469-y