|Budget Amount *help
¥3,600,000 (Direct Cost : ¥3,600,000)
Fiscal Year 1995 : ¥1,200,000 (Direct Cost : ¥1,200,000)
Fiscal Year 1994 : ¥2,400,000 (Direct Cost : ¥2,400,000)
In experimental studies of motion of fluids by means of optical measurement, flow behind an immersed solid body can not be visualized. If the body is transparent and the refractive index is equal to that of the fluid, light from the back of the body goes straight through it into optical sensors such as a photodiode, a CCD videocamera, etc.
Refractive index of water is 1.33 and that of pure silica glass is 1.48, which is lowest among those of usual glasses. Some special glasses such as F2Be-glass, which is strongly poisonous, two- or three-phase glasses of FLi, FNa, F2Mg, F2Ca and F3A1, which are difficult to make thicker than 1mm, have refractive indices lower or close to that of water. They, however, cannot be applied to practical use.
Addition of some chemicals usually increases the refractive index of water. However, too much chemicals considerably changes other characteristics of water such as density, viscosity, etc.
The present study found some preferable combination of additive chemicals and transparent low-refractive materials. The best among them, so far, is the combination of solution of 40%-NaI or KI of water and a low density silicon rubber ; both refractive indices are 1.40.
A technology to automatically track moving immersed bodies is also developed. They are applied to measure interaction of motions of water and immersed moving bodies, coupled with high-performance PTV algorithm which have already been developed by the authors.