Debris flows over erodible boundaries in narrow channels - Dr. Chi-Yao Hung, National Chung Hsing University - Taiwan
Chi-Yao Hung, Assistant Professor in the Department of Soil and Water Conservation at National Chung Hsing University in Taiwan
Abstract: Granular avalanches flowing over loose beds evolve by gaining or losing grains through their basal boundary as stress and velocity change within the sheared layer. In addition, the erosion of the side boundary also significantly affects the entraining progress. Here we first proposed a general depth-averaged theory for dry erosive flows in a non-uniform channel using balance equations for mass, momentum, and (crucially) kinetic energy. We assume a linearized $\mu(I)$ rheology for granular deformation and Coulomb friction along the sidewalls. The theory predicts the kinematic behavior of channelized flows under various conditions, which we first test in two sets of experiments: (1) a linear chute, where abrupt changes in tilt drive unsteady uniform flows; (2) a rotating drum,to explore steady non-uniform flow. Next, to investigate the possibility of wall erosion, we scale up the granular stress by performing the experiments under enhanced gravity conditions in a geotechnical centrifuge. Also, by incorporating Coriolis force the model can treat behavior under centrifuge-induced enhanced gravity. We develop an erosion model based on the kinetic energy exchanges through theory and experiment observation. The proposed erosion model can be applied to local erosion patterns and global erosion rates.
About the speaker: Dr. Chi-Yao Hung is an Assistant Professor in the Department of Soil and Water Conservation at National Chung Hsing University in Taiwan. He received a bachelor degree from the Department of Soil and Water Conservation in National Chung Hsing University, Taiwan, and received his master and doctoral degrees from the Department of Civil Engineering, National Taiwan University in Taiwan. Dr. Hung has worked as a visiting scholar at Columbia University and Aix-Marseille University before joining National Chung Hsing University. Dr. Hung's research interest is morphological hydraulics. This subject includes disasters on hill slope, fluvial geomorphology, and landscape evolution. His current focuses are debris flow simulation, landscape evolution, two-phase solid-liquid flows and morphological field investigations. A major research goal is using fundamental fluid mechanics and applied mathematics to solve these interesting morphological hydraulics problems.