|
Yamamoto Team
Prof. R. Yamamoto and Dr. S. Yasuda (Yamamoto Team) applied successfullytheir new multi-scale modeling method to analyze the complex behavior of polymer melt between rapidly oscillating plates.
Ryoichi Yamamoto(Professor, Department of Chemical Engineering, Kyoto University)
Shugo Yasuda(Assistant Professor, Department of Chemical Engineering, Kyoto University)
Abstract:
As a part of Basic Research Programs of JST (Japan Science and Technology Agency), Professor Ryoichi Yamamoto and Dr Shugo Yasuda have developed a multi-scale simulation method that combines molecular dynamics and computational fluid dynamics. They have also clarified successfully the complex flow behaviors of polymer melts in rapidly oscillating plates.
A lot of products in our daily lives contain soft matters (e.g. colloids, polymers, and liquid crystals). One of the most unique characters of soft matters is that they exhibit both solid- and liquid-like responses to mechanical strains or shape deformations. When computer simulations of fluids are performed, either computational fluid dynamics (CFD) or molecular dynamics (MD) is usually employed. In the case of CFD, mechanical properties of fluids must be modeled mathematically in advance as a form of “constitutive relation” to be used in simulations. CFD is thus valid only for the cases in which both mechanical properties of fluids and the flow profiles are not too complex. Polymer melts, however, have very complicated mechanical properties in general, and their flow profiles are complex in rapidly oscillating plates. In the case of MD simulation in contrast, fluids consist of huge numbers of molecules of arbitrary shapes. It is thus applicable for any flows of any complex fluids in principle. However, the drawback here is enormous computational time required to resolve the dynamics of all the molecules consist of fluids. Hence, MD simulation is not yet applicable to problems which concern large scale motions far beyond the molecular size, as is done in the present study. (An expected time to simulate only a gram of fluid would exceed one hundred years even if the rapid progress of computer continues forever.)
R. Yamamoto and S. Yasuda have developed a novel multi-scale simulation method which combines MD and CFD in order to overcome the weaknesses of the individual methods mentioned above. They have applied the new method for analyzing complex flow behaviors of polymer melts in rapidly oscillating plates. This is a model case for flows of lubricants in contact with fast moving parts in micro devices, such as hard disc drives or micro motors. The present results are expected to contribute toward innovations of new materials and applicable to variety of fields of materials science.
The present study will appear in “Europhysics Letters (EPL), 86 (2009), published online on 20th April 2009.
|
