MASHIKO Laboratory

In emergent situations where a large number of people are involved, it is obviously important that all the people escape to safety as quickly as possible. The efficiency of evacuation is strongly affected by various factors, such as the size or position of the exit or corridor, behavior of evacuees, existence of obstacles. We conduct numerical simulations of crowd evacuation to investigate such effects and seek for methods for quick evacuation.

In the study of multibody systems, each object is usually treated as a particle with minimum excluded volume, or at most as a rigid body with shape or size effect. What happens if each object can change its form? Through numerical simulations of “Flexible Chainlike Walkers”, we have found that the flexibility of each objects causes peculiar group phenomena, such as the spontaneous irreversible aggregation, freezing transition to complete jamming, and flow enhancement by countercurrent.

Thermal convection, which occurs when a fluid is heated from the bottom and cooled from the top, has been studied for a long time. Its behavior strongly depends on the fluid properties such as the viscosity. What happens if the fluid undergoes a phase change and hence a sharp change in its properties due to the temperature change during convection? We conduct experiments using such thermo-sensitive fluids to elucidate the effect of the phase change on thermal convection.

The brownfiled land, which is not in use due to potential contamination, has been recognized as an environmental issue. Conventional methods of decontamination have difficulties in space, time, or cost. A method overcoming these difficulties has been recently proposed; hot air is injected into soil, which gasifies the contaminant, then the gas is pulled from the soil, which is finally decomposed on the ground. We experimentally study the hot-air behavior in soil to put this method to practical use.

The air cell, a plastic bag with air inside, can be used as a cushion material, which is light and space-saving. Moreover, the air-cell cushion is expected to prevent pressure ulcers, utilizing the body-pressure dispersibility and depressurization effects of air cell, which is a distinct advantage, especially in the aging society. We study the effects of cell size, shape, air pressure, body curvature, etc. on the body-pressure distribution, which is essential in designing air-cell cushions of practical use.