碩士 / 國防大學中正理工學院 / 造船工程研究所 / 92 / Using the micro-bubble technique to reduce the skin-friction resistance of hull is estimated in this study. By effectively controlling the size of microbubbles, the spread of concentration, and the capacity of air supply, we are going to expect to reduce obviously the drag of ship. If one can get a reliable way that would be able to reduce effectively the frictional drag inside the turbulent boundary layer for ship hull, the total resistance of ship would be lowered evidently so that the practical benefit is to increase the speed of ship and reduce the noise decibel (dB). Therefore, not only the maneuver performance of ship can be improved, but also the energy resources will be saved.
The efficacy of drag reduction is quite high as the micro bubbles are applied to reduce the skin-friction resistance for a vehicle that moves in the sea, but there are many factors to influence the efficacy of drag reduction. The proceeding of experiment is mainly divided into two parts. First, we did the preliminary discussion in the way of producing micro bubbles and the mechanism of controlling parameters; we have established a vertical circulating water tunnel of high speed as the experiment platform in order to set up the experiment environment of turbulent boundary layer in which micro bubbles act on. Next, the total resistance of ship model was tested in a large horizontal circulating water channel for the sake of estimating the efficacy of drag reduction by using the micro-bubble technique to warship.
In order to produce the efficacy of drag reduction, the micro bubble drag-reduction technique must be employed in turbulent boundary layer flows. On the water tunnel test and the ship model test, the efficacy of drag reduction increases with increasing the quantity of micro bubbles supplied provided that the void fraction don''t go beyond critical values. In the present study, we have found that more regions cover with micro bubbles, more the efficacy of drag reduction be got; the maximum efficacy can reach up to 30%.
| Identifer | oai:union.ndltd.org:TW/092CCIT0345007 |
| Date | January 2004 |
| Creators | Tao Derong, 陶德容 |
| Contributors | 吳聖儒 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 66 |
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