| Summary: | 碩士 === 國防大學理工學院 === 造船及海洋工程碩士班 === 97 === The main task of underwater weapons is capable of hitting the target fast and precisely. Due to the constraint on the finite space, the underwater weapon is merely able to consist of necessary maneuver and propulsion devices except warhead. Hence, if some appropriate ways for reducing the drag of underwater weapons could be found, the consumption of energy resources will be decreased effectively. Meanwhile, it could improve the operating performance, increase the voyage distance, and restrain the noise radiation of the underwater weapons. Therefore, the research of the drag reduction of submerged bodies has been the important issue among advanced countries.
The first stage of the work in this research is to study the effect of drag reduction of the underwater weapon by polymer coating technique. The controllable factors may include the coating way, coating material, and depth ratio H/d. The flow speed is regarded as the indicative factor. The best polymer coating is screened for drag reduction.The second sage of the work is to discuss reducing the drag of the underwater weapon by the combination of polymer coating and micro-bubble technique. At this stage, the controllable factors may include the depth ratio H/d and the generating rate of micro bubble. The flow speed is still regarded as the indicative factor. Then, “Design of Experiments (DOE)” is used to choose the best level of controllable parameters for getting the robust design. Meanwhile, the influence of those controllable factors on the drag reduction of the underwater weapon was discussed.
The experimental results of the first stage revealed that it may get the lowest drag in the spray of super-hydrophobic coating. The experimental results of the second stage revealed that the best effect on the drag reduction was up to 45% at the lower flow speed and higher generating rate of the micro-bubbles. The method of Taguchi’s orthogonal array was employed to analyze the results of the experiment in order to gain the optimum and robust parametric condition for combining the polymer coating and the micro-bubble technique. It is estimated that 16% drag reduction for the underwater weapon has been obtained after choosing the optimum conditions from the Taguchi analysis.
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