Research Topics
Representative Research Examples
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Elucidation and control of the molecular mechanism that determines thermal transport via molecular dynamics simulation
Advanced thermal management is urgently needed to further improve the performance of semiconductor electrical components. Therefore, there is a need for technology to design heat medium and thermal interface materials with desired properties at the molecular level. In order to enable such “molecular design,” it is necessary to understand the molecular scale mechanism of macroscopic heat conduction. However, compared to solid crystals and gases, the molecular arrangement and motion of liquids, soft matter, and their interfaces are irregular, making it difficult to research.
In the present research, we have developed an analytical method via molecular dynamics simulations to express macroscopic heat conduction as an accumulation of microscopic energy transfer due to interactions between individual atoms and molecules (i.e. atomic heat path, see upper subfigure). By doing so, we have clarified the connection between the molecular structure, functional group characteristics, and heat transport in self-assembled monolayers (SAMs) at the solid-liquid interface (lower subfigure). -
Aircraft design based on fluid-structure interaction analysis and multi-objective optimization
In the aircraft design, it is essential to consider the interaction between aerodynamic forces and structural deformation through fluid-structure interaction analysis, and to conduct multi-objective optimization, such as minimizing aerodynamic drag and structural weight. In this study, we developed an aircraft design tool for carbon fiber reinforced plastic (CFRP) materials, which is named as the Digital Aircraft deSign tool of ToHoku University: DASH [1]. This tool enables material property prediction through multiscale analysis, aeroelastic analysis of CFRP wings under various flight conditions, structural optimization with aeroelasticity, and multi-objective optimization of wing geometries using Bayesian optimization. In particular, we have successfully quantified the changes in wing performance due to differences in carbon fibers, and clarified the effects of reduction on structural weight and wing deformation when using the next-generation carbon fiber, TORAYCA®T1100G [2]. Currently, we are also developing design tools for aircraft with complete configuration, while also conducting fundamental research on coupled analysis methods to apply more advanced and high-fidelity simulations.
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Theoretical Design and Control of Liquid-Liquid Phase Separation Using Artificial Proteins
It is known that proteins and RNA can self-assemble to undergo liquid-liquid phase separation, forming droplets or gel-like structures within cells. In the crowded and chaotic intracellular environment, these droplets create order by concentrating specific molecules while excluding others, thereby regulating various biological processes such as transcription, translation, and signal transduction. However, it is challenging to experimentally observe the internal structure of such dynamic and reversible droplets at atomic resolution, and current methods rely on trial and error when exploring the types and combinations of constituent molecules. In this study, we aim to theoretically design artificial proteins that undergo phase separation using molecular simulations, in order to elucidate the mechanisms of droplet formation and control their fluidity. In collaboration with experimental groups, we also synthesize and evaluate these proteins experimentally, working towards a bottom-up understanding of intracellular phase separation. Additionally, we seek to develop methods for controlling the function of specific proteins within cells by selectively trapping them inside droplets.
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Laminar-turbulence transition phenomena near the leading edge of a swept wing
When a commercial aircraft operates, about half of the total energy loss is due to the friction due to the viscosity of the air. Turbulent flow makes the friction increase, but 10% of the total energy loss can be reduced if the laminar flow can be maintained 50% on the wing. Recent advances in numerical simulation technology and surface processing technology have made it possible to expect higher performance than ever before, therefore it has been attracting attention in recent years. It is known that the main wing of a passenger aircraft has a swept angle to reduce the effect of shock waves, which complicates the flow and causes a unique laminar-turbulent transition phenomenon. By carrying out direct numerical simulation by large-scale parallelization, we aim to clarify the details of the transition mechanism on the swept surface, improve the accuracy of the transition prediction strategy, and propose a new laminarization technology.
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Blood flow analysis in a left ventricle
The thrombus formation has been assumed not to occur in a left ventricle, which works as a pump sending a blood to a circulatory system, because of its high blood flow velocity. However, resent studies indicated the thrombus formation might occur in the left ventricle.
This study investigates the blood flow in the left ventricle using the left ventricle model considering representative internal structures in the left ventricle with the supercomputer in Institute of Fluid Science. Figures are the visualization of vortex structures in the left ventricle models without (left) and with (right) the internal structures. The white surface shows shapes of the vortex. The vortex structures do not reach an apex of the left ventricle in the case where internal structures exist. Various parameters besides the vortex structure also show that the tendency blood flow stagnates becomes high by the internal structures. Moreover, the study on the effect of valvular heart diseases has been proceeded using this analysis technique. -
Elucidation and Control of the molecular mechanism that determines thermal conductivity of heat medium
Reproduced with permission by Elsevier from Fluid Phase Equilibria, 441, p.24 (2017)
Modern industrial products, typified by electronic devices, are required to be supported by advanced thermal management such as control of heat generation and dissipation, and correspondingly there is a demand for the technology that enables us to customize precisely the properties of heat medium based on the molecular aspect. The knowledge about the molecular scale mechanism of macroscopic heat conduction is inevitable for the realization of such ‘molecular design’ of heat medium. However, the studies of such mechanism in liquids and soft materials, where the molecular configuration and dynamics are irregular, are not sufficient when compared with those of gas and crystalline solids.
In the present research, on the basis of molecular dynamics simulation, we developed a method to express macroscopic heat conduction as an accumulation of microscopic energy transfer due to single interaction (i.e., the atomistic heat path, see the upper subfigure) between atoms and molecules. Using this method, for typical liquids including alkanes and alcohols, we have clarified the connection between the molecular features, like backbone structure and functional groups, and thermal conductivity. In recent days, on the other hand, the nano-composite materials where carbon nanomaterials (see lower subfigure) in the forms of nano-particles are dispersed in a matrix, are attracting much attention as promising heat media; analysis is also ongoing with such materials.
(Joint research, Toyota Motor Corporation)