Studies on nonequilibrium phenomena in gas flows-New approach by hybrid micro-macro gasdynamics-

1.稀薄气体的二维Benard问题是日本（JG）和意大利（IG）两个小组共同研究的问题。JG发现了一个新的边界的参数区域的稳定的解决方案，没有流动，这在经典的流体动力学是未知的。JG还研究了多滚解的稳定性，阐明了从不稳定多滚解到稳定多滚解的过渡过程。IG用直接模拟蒙特卡罗（DSMC）方法给出了一个具有混沌行为的流的例子. JG研究了由气体的凝聚相构成的两个同轴圆柱之间的Couette流的分叉。首先，在只有内筒转动的情况下，通过DSMC方法对初值问题进行分析，研究了分岔的结构，阐明了初始条件与稳定定常解之间的关系。其次，在一般情况下，外圆柱也旋转，系统渐近 关于我们 分析是在圆筒旋转缓慢和气体稍微稀薄的条件下进行的。从而全面地阐明了分歧的结构，并发现了各种新的分歧解类型. JG进行了一项实验研究，研究了利用温度场诱导的稀薄气流进行真空泵的可能性。结果表明，该泵的流动与数值预测的流动相一致，证明了该泵的实用性。JG还总结了前人在温度场诱导下稀薄气体流动的研究结果，包括本实验. JG公司全面系统地总结了冷凝到其冷凝相的气体流动的现有结果，并将信息提供给了IG.5。JG和IG合作研究了无限强冲击波的结构，并通过JG开发的有限差分方法澄清了速度分布函数中的奇异性。JG还开发了一个数值计划的精度更高的时间依赖性问题的玻尔兹曼方程。少

1. The two-dimensional Benard problem for a rarefied gas was studied by both Japanese group (JG) and Italian group (IG). JG found a new bound of the parameter region for a stable solution without a flow, which has not been known in classical fluid dynamics. JG also investigated the stability of multi-roll solutions and clarified the process of transition from unstable multi-roll solutions to stable ones. IG showed an example of the flow with chaotic behavior using the direct simulation Monte Carlo (DSMC) method.2. JG studied bifurcation of the Couette flow between two coaxial circular cylinders made of the condensed phase of a gas. First, in the case where only the inner cylinder is rotating, the structure of the bifurcation was investigated by analyzing the initial-value problems by the DSMC method, and the relation between the initial conditions and the stable steady solutions was clarified. Next, in the general case, where the outer cylinder is also rotating, a systematic asymptotic … More analysis was carried out under the condition that the rotation of the cylinders is slow and the gas is slightly rarefied. As a result, the structure of the bifurcation was clarified comprehensively, and various new types of bifurcated solution were discovered.3. JG performed an experimental study of the possibility of a vacuum pump using a rarefied gas flow induced by temperature fields. As a result, a flow consistent with the flow predicted numerically was observed, and the practicality of the pump was demonstrated. JG also summarized the previous results for the rarefied gas flows induced by temperature fields, including this experiment.4. JG provided a comprehensive and systematic summary of the existing results for flows of a gas condensing onto its condensed phase and gave the information to IG.5. JG and IG cooperated to study the structure of an infinitely strong shock wave and clarified the singularity in the velocity distribution function by means of a finite-difference method developed by JG. JG also developed a numerical scheme of higher accuracy for time-dependent problems of the Boltzmann equation. Less