In the community of turbulence and turbulent combustion research, results obtained from direct numerical simulations and advanced laser diagnostics are regarded as forming the fundamental basis of physical insights and mathematical models of the highly non-linear, multi-physical phenomena. Over the decades, we have contributed in these research areas by means of these numerical and experimental approaches, and tried to ellucidate relevant physical mechanisms. The scale of these simulations or laser diagnoctics has improved over the years thanks to the advancement of high performance computing, numerical schemes, and laser and optical systems. The insights based on these numerical and measured resutls are then applied to develop mathematical models to describe microscale non-linear acitivities incorporating theories, which could be used for computational fluid mechanics of major combustion devices.

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Effects of tube diameter (34mm, 22mm, 14mm) and inclination on performance of thermosiphon type heat pipe are investigated experimentally. Pure water and aqueous solution of surfactant (potassium oleate) are used as a working fluid. Then relation between inside flow and thermal resistance is studied. Thermal resistance of 22mm heat pipe is the lowest among the test heat pipes for both pure water and aqueous surfactant solution cases. When heat pipes are active in their operation and have lower thermal resistances, strong boiling that blows liquid working fluid to the condenser section is always happened. For tilt angle of 0°~75° from the vertical, the larger the tilt angle is, the lower the thermal resistance is under all experimental conditions. Thermal resistance of vertical 34mm heat pipe using surfactant solution (potassium oleate 300ppm) is reduced by about 60% at maximum under low cooling temperature and small heat transfer rate condition compared to that of pure water.

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