Study of Mechanism of Decompressible Cavitation Occurrence and Bubble Embolism in Blood

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It is known that decompression disease represented by submarine sickness causes disturbances of peripheral circulation owing to bubble formation in blood. However very little is known about the growth of micro bubble and the mechanism of the development. In this work, as purpose of clarification of physical mechanism of an outbreak of decompression disease, an apparatus for gas-liquid two phase flow with compression or decompression type was made by combinating a micro video device into a high liquid pressure vessel. The following experiments I and II were then carried out.In the experiment I,the occurrence of micro bubble in static liquid caused by the difference of the liquid pressure was studied.(1) The bubbles with radius of 0.5-2.0mm are generated in the liquid. (2) The bubble number density increases by an increment of the difference of liquid pressure. (3) The bubble number density of carbon dioxide is large as compared with air bubble.In the experiment II,the gas-liquid two phase flow in the channel was studied in gas over saturated liquid as working fluid. The following results were obtained.(1) The micro bubbles with radius 20-100mum are generated in the channel, and after the bubbles grow rapidly during 0.6-3sec. The growth rates increase with an additional gas pressure into the liquid. (2) The growth rate of air bubble for flow velocity 0.5m/s is four times as large as for 2.3m/s. (3) The air cavity grows with rate of about 2.4m/s, and the maximum size is 5mm in width and 14mm in length. (4) The diameters of micro carbon dioxide bubbles are 20-200mum. The growth rates of carbon dioxide bubbles are 5-80times as large as the rates of air bubbles.