永田 靖典

<p>In semiconductor production, efficiency and precision of the cleaning process is important. In this study, we handle "Single Wafer Cleaner" that is one of the washing methods in the way of blowing air to a wafer with a turning disk at a high speed. However, the flow in the device becomes turbulence, which causes a problem that water drops and dusts re-attach to the wafer. It is necessary to understand the flow in the device. In previous investigations, we were able to get knowledge of the detection of vortices using numerical computation and Particle Image Velocimetry analysis in using the simplified experiment model. Therefore, we tried to understand the detection of large-scale vortices combining speed data and the unsteady pressure data. We measure pressure using microphones and perform the frequency analysis and cross correlation of the data. In doing so, we have get the knowledge of the vortical structure.</p>

<p>It is known that the critical Reynolds number of turbulent transition in the straight-pipe flow is about 2300. However, it is reported that turbulent transition is delayed when there are micro-bubbles in water. And the drag was reduced in same Reynolds number range. To confirm the effect of the drag reduction, it is important to make a laminar flow at the entrance of the test section. To keep flow stable, we ensure the long entrance section of about 4 m. Then we measured the differential pressure and calculated friction factor in the straight pipe with circular cross section. The inner diameter of the pipe is 20 mm. In this experiment, turbulent transition took place at the same Reynolds number range when we use water with micro-bubbles and without micro-bubbles.</p>

The aerodynamic force enhancement effect occurs by applying magnetic field around a reentry vehicle in a weekly-ionized flow behind the strong detached shock wave. Recently, this force enhancement effect was experimentally investigated using an expansion tube which can produce high speed and high enthalpy flow. Because aerodynamic force measurement is difficult due to short test flow period in expansion tube, drag measurement system which employed a piezofilm with fast responsiveness was developed in this study. This drag measurement system was calibrated using CO2 pulse laser and applied to experimental investigation on the aerodynamic force enhancement effect in expansion tube. The aerodynamic force acting on simple models in the flow produced by the expansion tube can be measured in this system. Additionally, the increase of the drag force due to magnetization in a weekly-ionized flow was observed.