Author(s): Muneyuki Arai; Xuelan Liu
Linked Author(s): Xuelan Liu
Keywords: Viscous debris flow; PIV method; Surface velocity; And mechanism
Abstract: Some debris flow that the volume concentration of solid is about or over 70% is called ¡°viscous debris flow¡± in China. Due to the importance for understanding the real phenomena of debris flow events, a PIV (Particle Image Velocimetry) method is conducted to analysis the surface velocity of it. With analyzing the recorded data in field, some results were obtained: the Eulerian velocity change in the central part of surges; the surface velocity distribution in cross section; and the surface velocity vector distribution in a surface area. According to these results and the field experiment data, it could be concluded that the structure of debris flow is complex in a surge. And the structures are different in the different scale surges. The surface velocity is fastest in the front of surge, and decrease till the end of the flow. In the front of flow, large-scale surges and small-scale surges flow as the turbulence and the lamina, respectively. And in the rear of flow, both two scales surges could be considered as laminar flow. The end of the flow almost stops in the channel. And this process is relatively slow. It illustrates that the cohesive stress is independent of the velocity gradient dominated the flow. Therefore the value of the cohesive stress is very small.
Year: 2001