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Transition of diffusion mechanism from molecular thermal motion to macroscopic temporary fluctuation
Fan J(樊菁)
Source PublicationProceedings of 29th International Symposium on Rarefied Gas Dynamics/AIP Conference Proceedings, v.1629
2014
Conference NameThe 29th International Symposium on Rarefied Gas Dynamics
Conference Date2014-07-13
Conference Place中国陕西西安
AbstractTwo different mechanisms of the diffusion of gas are studied numerically and analytically. In the numerical study, the diffusion coefficient of argon gas between two infinite parallel plates is calculated based on the Einstein relation. The molecular displacements in the directions parallel to the plates are obtained using the DSMC method. The diffusion coefficients so obtained are compared with those predicted by the Chapman-Enskog theory. They are in excellent agreement when the distance between the plates h=50lambda, but become much different when h=50lambda. An analysis reveals that molecular collisions have two-fold effects: viscous damping and nonlinear excitation. When macroscopic temporary fluctuation appears, no matter resulting from an external disturbance or from a local non-uniformity, due to the viscous damping effect reduces as the Knudsen number decreases, the diffusion coefficients in the x and z directions without the solid walls restraint change greatly with time, and deviate from the Chapman-Enskog theory that does not take into account the macroscopic temporary fluctuation. This indicates that under an external disturbance or a local non-uniformity, a transition of diffusion mechanism from molecular thermal motion to macroscopic temporary fluctuation occurs as the Knudsen number decreases.
DepartmentLHD微尺度和非平衡流动
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Language英语
Document Type会议论文
Identifierhttp://dspace.imech.ac.cn/handle/311007/55213
Collection高温气体动力学国家重点实验室
Recommended Citation
GB/T 7714
Fan J. Transition of diffusion mechanism from molecular thermal motion to macroscopic temporary fluctuation[C]Proceedings of 29th International Symposium on Rarefied Gas Dynamics/AIP Conference Proceedings, v.1629,2014.
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