Fluid Dynamic clarification of Bubble Generation Phenomena in Human Body under the Decompressed Environments

潜病是一种由人体在潜水过程中产生的水疱引起的疾病，但其发病的动力学机制尚不清楚。本文从流体力学的角度对人体内气泡的产生进行了实验和理论研究。首先，制作了压力变化液体中气泡形成的实验装置，用于模拟深海环境条件。应用该装置进行实验，发现随着压力容器减压程度的增加，液体中的气泡密度增大，并且随着最大附加压力的增加，这种趋势更为明显。由于二氧化碳溶解在液体中，液体中的气泡密度是空气的3 - 5倍，并且观察到一些直径约2mm的较大球形气泡。对于溶解空气，减压液中出现半径约为1mm的球形气泡。研究了水和人体血液中高速旋转圆盘周围的空化现象。在血液中，空化发生的雷诺数比在水中低。血液中的空化噪声水平高于水中。结合气泡运动方程和气体扩散方程进行了数值计算。结果表明，气泡的生长速率随时间的增加而增大，气泡的最大半径随海水深度的增加而增大。小气泡受气体扩散的影响，气泡的生长速率变大。

Submarine sickness is taken ill with vesication in dived human body, however very little is known about the dynamic mechanism of the sideration yet. The purpose of this report is to study experimentally and theoretically the bubble generation in human body from a viewpoint of fluid dynamics. First, the apparatus about bubble formation in liquids with pressure variation was manufactured for trial, which used to model for the environmental conditions in deep sea. By making the experiment applied this apparatus, it is found that the bubble density in liquid becomes high with increasing the decompression in the pressure vessel, and that the tendency is noticeably with an increment of the maximum additional pressure. As carbon dioxide was dissolved in liquid, the bubble densities in the liquid are three-quintuple times as compared with air, and some relatively large spherical bubbles with about 2mm in diameter are observed. For dissolved air, the spherical bubbles whose radii are about 1mm appear in the decompressed liquid. Cavitation phenomena around a high-speed rotating disk were studied in water and human blood. In blood, cavitation occurs at lower Reynolds number than in water. The cavitation noise level in blood is higher than in water. Numerical calculations were conducted by combination of the equation of motion for a bubble and the diffusion equation of gas. As a result, the bubble growth rate increases with the elapsed time, and the maximum radius of the bubble is large with the depth in sea. Small bubbles are affected by gas diffusion, consequently the growth rates of bubbles become large.