The objective of this study was to compare the swimming performance between animals and machines. For this objective, the characteristics of the swimming as a locomotion style were discussed first. The design strategies of the swimming animals were next described for three scales. Finally, the comparison between the animals and machines with respect to the propulsive efficiency was carried out. For the small and medium scales, there was no report with respect to the propulsive efficiency for the machines, while the several percent for the small scale and 45〜50% for the tadpole were reported, respectively. For the large scale, the propulsive efficiency of the animals was comparable to the high-performance type screw propeller.

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Insect flight is now an active and well-integrated research area, attracting participation from a wide range of talents. Not only because nature has bred astonishing solutions to this complex real world challenges but also it offers us a perfect objective of biologically inspired engineering research, which could lead to a greater understanding of novel biomechanisms on the "intelligence" of a flying insect and a breakthrough for designing and building small-scale flying mechanical devices, namely, Micro Air Vehicles (MAVs). This paper showcases our recent works associated with computational biomechanics with a specific focus on novel biomechanisms in insect flight and insect-inspired MAVs development.

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Rheological properties of magnetorheological (MR) fluid were influenced by the cluster formation. The cluster formation appears when an external magnetic field is applied in MR fluids. Hence, we propose an experimental analysis of these structures by measuring properties of ultrasonic wave propagation precisely. The ultrasonic technique can be applied to an opaque fluid, such as MR fluid. The ultrasonic propagation velocity can be found by the pulsation methods. Based on these results, the clustering structures of these fluids are analyzed experimentally in term of temperature, effect of the external magnetic field and hysteresis phenomena. The absolute value of ultrasonic propagation velocity decreases as the volume fraction of particles increases when no magnetic fields. Hysteresis on MR fluids always comes back to the initial value. This occurrence is caused by the clusters formation that is proportional to magnetic field intensity. It seems that cluster formation in MR fluids becomes to the initial condition after the external magnetic field intensity is zero.

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Since the conservation equation of turbulence kinetic energy (TKE) involves correlations among local instantaneous gradients of fluctuating velocities, it is indispensable to measure the velocity gradients as well as the velocity components. The authors developed a molecular tagging method using photobleaching (PB-MTV), which can measure not only velocity but also its gradient by making use of the translation and deformation of a tag. We applied the PB-MTV to turbulent bubbly flows in a square duct. The experimental results indicate that the presence of bubbles increases not only the production rate but also the dissipation rate of TKE. Although the low Reynolds number k-z model well evaluates the production rate of TKE in the bubbly flow, modification of the diffusion term is required for the bubbly flows.

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This article describes the important problems remaining in boiling research. There are many sub-processes in nucleate boiling but the most important one may be the heater surface characteristics including nucleation site density, activation and deactivation of nuclei, effects of thermo-physical properties of boiling liquid and a heated surface. Another problem may be the numerical simulation of boiling phenomena. There are two possible methods of simulation, i.e. strict numerical calculation and model simulation. In this article, the new style of research of boiling is also proposed.

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The present study described applicability of micro shot peening treatments as a tool for surface modification. The developed peening apparatus having a direct gas injection system was consisted from the double walled nozzle and the particle storage tank enclosing rubber balls and was possible to fabricate the surface texture consisted from isolated micro dimples resulted from individual particle impacts. The friction coefficient of the micro dimpled texture surface was approximately 0.003 mated with parallel grooved surface in lubricated condition. In addition, it was possible to apply oil repellence and functional gradients to the surface using mixed particles as the impact media. It was confirmed that the application of the oil repellence was effective for the decrease in the friction coefficient on higher sliding speed region and that the anti wear property of the functional gradient surface was excellent on the abrasive wear condition.

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