| Co-Investigator(Kenkyū-buntansha) |
HOSOKAWA Shigeo Kobe University, Graduate School of Science and Technology, Associate Professor, 自然科学研究科, 助教授 (10252793)
TOMIYAMA Akio Kobe University, Graduate School of Science and Technology, Associate Professor, 自然科学研究科, 助教授 (30211402)
|
|---|
| Research Abstract |
Though a space-time evolution is one of the most intrinsic natures of gas-liquid two-phase in a vertical pipe, there is little available numerical method for the prediction of the spatial evolution and the transition of flow regime. Detailed numerical methods such as an interface tracking method can predict detailed phase distributions, which play a dominant role on spatial evolution. These method however need models or assumptions on processes of spatial evolution such as bubble coalescence and clustering, and the application of these method to industrial design is not realistic due to the huge CPU time. The purpose of the present study is to develop a one-dimensional gas-liquid two-phase flow model for whole flow regime in a vertical pipe. In order to make up for the lack of database on spatial evolution, we carried out two-phase flow experiments in a vertical pipe, and investigated spatial evolution of volume-averaged void fraction, void fluctuation and flow pattern evolution caused
… More
by the bubble clustering and coalescence Phenomenological models for the spatial evolution were developed through the experimental results, and one-dimensional one-way bubble tracking simulation with these models was developed and evaluated.
It was confirmed through the experiments that (1) the spatial evolution of flow pattern is dominated by the bubble distributions rather than the mean void fraction, (2) bubble clustering plays a dominant role in the evolution, (3) bubble coalescence and bubble clustering are hindered by the presence of shear-induced turbulence, but they are enhanced with increasing the void fraction, (4) the rising velocity of a bubble cluster is almost equal to that of a Taylor bubble in the same size, (5) the impact of wake behind large bubble on the motion of small bubbles increases with decreasing the liquid flow rate, and (6) the void fluctuation increases along the flow direction due to the growth of bubble clusters and Taylor bubbles.
Phenomenological models were developed based on the experimental results, and applied them to one-dimensional bubble tracking method. The developed simulation method includes a model of radial distribution of bubbles, and the time for the simulation is almost the same with the actual phenomena. The simulated flow pattern evolution, averaged void fraction and void fluctuation were agree well with the experimental results of two-phase flow in stagnant liquid, laminar and turbulent liquid flow. Less
|
