Three-dimensional unsteady computations by RANS model simulation and large eddy simulation (LES) of impinging gas jet on a liquid surface were carried out. Results of the simulations were compared with experiments. Time-average values of cavity depth obtained by both simulations are consistent with those of the experiments. Prediction accuracy of LES is better than that of RANS model simulations in dynamic behavior of cavity depth as well as detail of cavity shape.
The expansion and shape change behaviors of a single rising bubble in a reduced pressure vessel were observed. The main results obtained are as follows: 1) The aspect ratio, h/w, of a single rising bubble under reduced pressure is almost the same as that under atmospheric pressure. However, the width of the rising bubble expanded to 1.4 times, which is larger than the calculated expansion ratio. This may be explained by the change of the bubble shape while rising. 2) The observed single bubble shapes were ellipsoidal, spherical-cap, and breakup of spherical-cap. The upward velocity of the bubble increases with the initial volume of the bubble. The upward velocity also increases as the bubble rises.
Experiment and numerical simulation of RH circulation flow were carried out on water model. Helium gas was injected into water in up-leg and flow rate was estimated at the end of down-leg. Volume of fluid(VOF) simulation was also performed by compressible Inter Foam solver of OpenFOAM, open source CFD toolbox. Three pairs of diameter of up/down-leg,100mm/100mm, 140mm/70mm and 170mm/30mm were estimated and the circulation flow rate by numerical simulation was almost consistent with measurement. Finally the simulation with scaled up mesh and molten steel properties was carried out. The volume of injected gas became larger according to rising in the up-leg because of hydrostatic pressure distribution and the behavior of gas-liquid interface in vessel was simulated qualitatively.
Coagulation of particles in the fluid is often observed in nature and it is a multiphase phenomenon utilized in various processes. Coagulation phenomenon is also observed in molten metal system in the same as water and air system. Until now, coagulation of particles such as oxide inclusions, have been focused on because large inclusions raise harmful defects in final products. Therefore, many researches have been performed in the both side of theory and experiment. In this paper, kinetics of coagulation behaviors is summarized for information to analyze the growth rate of aggregates, particle size distribution and so on. In addition, recent researches and issues for coagulation mechanism are introduced briefly in the view point of multiphase phenomenon.
Characteristics of counter-current flow limitation (CCFL) inside vertical pipes with sharp-edged upper end (CCFL-P/SE) and with round-edged upper and lower ends (CCFL-P) were evaluated to clarify the dependence of the limiting locations. The CCFL is defined by the relationship between the gas and liquid volumetric fluxes (JG and JL) under a quasi-steady state after onset of flooding. CCFL correlations were constructed for CCFL-P/SE and CCFL-P based on the previous experimental data. The correlations were compared to the characteristics of CCFL at the vertical pipes of the sharp-edged upper end (CCFL-U) and the sharp-edged lower end (CCFL-L). CCFL-P has the highest liquid volumetric flux when CCFL occurs, and the lowest is CCFL-L. For the Wallis correlation, selection of the characteristic length of w = D(1-β)Lβ (where D and L respectively denote the diameter and the Laplace capillary length) is quite important. Our results have indicated that CCFL-P/SE and CCFL-P are also expressed by β ≈ 0.5, CCFL-U is expressed by β = 1, and CCFL-L is expressed by β = 0.