# ESR10 Xiannan Meng

Research project description

**Simulation of debris flow with mixture theory and CFD**

Fellow: ** Xiannan Meng**

Department: **Department of Machinery. Technical University of Darmstadt (TUD), Germany.**

Supervisor: **Prof. Dr.Ing. Yong-qi Wang**

Debris flows are dangerous natural hazards occurring in mountainous areas throughout the world. The flow mass consists of a heavy, dense mixture of water, sediment, and boulders of different sizes, which can cause tremendous devastation. It is in urgent need of a reasonable mathematical model which can describe the mechanism of debris flow from the stand points of an improvement of the prevention systems.

This project aims to develop a new generation of debris flow model combining Computational Fluid Dynamics (CFD) with mixture theory. The two-phase flow model is developed by exploiting mixture theory to take the multiphase property into account. As the first step, the constitutive model of the solid is modelled by simple Mohr-Coulomb plasticity theory. Furthermore, the sophisticated constitutive model for the solid will be developed based on rheology. For the fluid, Newtonian fluid is assumed. The coupling between the two phases can be achieved by considering complicated interactive forces. The resulting governing equations dominating the movement of debris flow are often strongly convective hyperbolic and parabolic equations, especially when shocking wave is formulated. CFD, as a branch of fluid mechanics, can solve and analyse problems involving fluid flows with high accuracy and efficiency. The complex governing equations can be solved numerically by sophisticated methods from CFD. The preliminary results from numerical simulation can be found in Figure.1 for 1D case.

Future cooperation research will be intended to validate the mechanics of viscous flows with the collaboration of Alessandro (ESR 9), Pablo Becker (ESR 11) and Miguel (ESR 14), and meanwhile, the constitutive model of the debris flow will be developed with the cooperation of Xiaogang (ESR 2).

*Figure **1**. **In figure (a) the red line denotes the fluid, and blue line denotes the solid. In figure (b) the distribution of the solid volume fraction varies with time.*