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

1. 日本（JG）和意大利（IG）研究了一种稀薄气体的二维Benard问题。JG发现了一个新的无流稳定解的参数区域边界，这在经典流体力学中是未知的。JG还研究了多辊溶液的稳定性，阐明了不稳定多辊溶液向稳定多辊溶液过渡的过程。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研究了由气体的冷凝相组成的两个同轴圆柱体之间的库埃特流的分岔。首先，利用DSMC方法分析了仅内柱旋转情况下的分岔结构，明确了初始条件与稳定解之间的关系；其次，在外筒也在旋转的一般情况下，系统的渐近分析，在筒体旋转缓慢，气体稍稀薄的情况下，进行了更多的分析。从而全面阐明了分岔的结构，并发现了各种新型的分岔解。JG对利用温度场诱导的稀薄气体流制造真空泵的可能性进行了实验研究。结果表明，该泵的流量与数值预测结果一致，证明了该泵的实用性。JG还总结了包括本次实验在内的前人关于温度场诱导稀薄气体流动的研究结果。JG对气体凝聚到其凝聚相流动的现有结果进行了全面和系统的总结，并将这些信息提供给了IG.5。JG和IG合作研究了无限强激波的结构，利用JG开发的有限差分方法澄清了速度分布函数的奇异性。JG还为波尔兹曼方程的时变问题开发了精度更高的数值格式。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