Other Abstract | Droplet migration problem in thermal radiation is a problem with great realistic significance, in a microgravity environment, a uniform droplet in mother liquor is uniformly radiated, then the droplet under the effect of uneven surface temperature will produce uneven surface tension, and the action of migration to the radiation direction under the uneven surface tension and eventually reach a steady state. This migration problem has some similarities with the thermal capillary migration caused by temperature gradient, but there are also many more complicated places.
In previous studies, there are only analytical solutions and deformation solutions of zero Re number, zero Ma number in terms of theory, and there is still a lack of in-depth research on the influence of nonlinear terms. This is because the analytical solutions and deformation solutions of zero Re number and zero Ma number are too complicated. In this case, the direct introduction of nonlinear terms will make the problem more complicated. This is also the main reason that hinders the theoretical research in this field. Numerically, there is a lack of analysis on the influence of Ma number on droplet migration and the change of temperature field after steady state. However, the research in this aspect is related to the physical mechanism of droplet migration, as well as the thought on the definition of steady state in this case. There are also more complex droplet migration problems under large Ma number. The
migration at large Ma number is quite different from that at small Ma number and medium Ma number, and the specific situation needs further study.
In this paper, the truncated approximation of the analytic solution is used to correct the migration and deformation problems under small Re numbers. The thermal capillary migration of an axisymmetric droplet under thermal radiation was numerically simulated by using the Front-tracking method. Under the condition of uniform thermal radiation, droplet migration reaches steady-state migration through nonlinear growth, and droplet migration velocity decreases with the increase of Ma
number. Further, the paper analyzes the temperature field changing situation in the change of droplet migration after reaching steady state and found that the temperature field is a approximate quadratic function of time after reaching the steady state with the dominating of linear growth, at the same time, the function of the whole temperature field changing with time is not uniform, but is related to the relative positions of observation point and the droplet. The closer to the droplet, the faster the temperature increases; the farther away from the droplet, the slower the temperature increases.
Microchannel migration problem in thermal radiation is very important in the field of biology and chemistry, the research progress in recent years, the radiation on the functioning of the droplets in microchannel exploring research also has a lot of experiments, such as the radiation on the manipulation of the droplet, the block of the droplet, the liquid column maintenance, etc., but also the lack of progress in terms of
value. This paper simulates the migration and deformation of the droplet under microchannel by introducing deformation and related revision programs, channel width influence of the droplet migration and deformation are analyzed, and Ma number influence on migration and deformation, found that the narrower the channel, the slower the droplet migration, the greater the deformation; the greater Ma number, the longer time to reach steady state, the smaller deformation. |
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