重力驅動顆粒-流體兩相流場之理論與實驗研究(3/3)

Fluid-granular mixture flows are motivated by various applications in industrial processes and predictions of natural hazards such as debris flows. A debris flow represents a gravity-driven flow of sediment particles andwater, which fills the interstices of granular material partially or excessively. Despite the past developments inmodeling, computing and experimenting geophysical mass flows, the prediction of such fluid-granular multiphaseflows is still a most challenging topic. In the first year of project, we will develop an indirect image measurement technique, which is coupled with PIV & PTV and used to measure the fluid velocities, the granular positions and velocities during the mixed flow field. The results show that because the addition of the solid particles, the fluid maximum velocity will be larger than the average velocity of the one phase flow. However, the fluid average velocity of two phase flow is lower than that of the one phase flow. The average velocity of particles will decrease with the fluid flow rate increase. As the particle size become smaller, the average velocity of particles will also decrease. In the second year of project, we mainly used the new measurement technology developed in the first year and built a two-phase flow rectangular chute to simulate the velocity under each characteristic time during the collapse. The reactions that occur when sand and water are filled at different filling heights are respectively explained. The experimental results found that the maximum speed of water and sand will show two turning points. This is because the energy absorption and feedback phenomenon generated after impacting to the bottom, and the height of water addition determine the fastest overall two-phase flow. It has also been observed that sand has a buffering effect on the overall flow. The higher the stacking height, the lower the flow rate of the overall two-phase flow. In the third year of project, the chute of the second year was used for reconstruction, and the collapse tests of different proportions of water and sand were set up, and the velocity distribution of the sand flow was measured for different characteristic times. It is found that the global filling of water and liquid will have a feedback phenomenon for the overall collapse, so that the distribution of the collapse velocity of the sand is obviously different from that of the local water filling, and the collapse time is decreased.The related research in this three-year project is to discuss and study the flow behavior of fluid-particle mixtures, and verify them through experiments. The research results are expected to be beneficial to the prediction and assessment of disasters in the future.