水中載具減阻技術之實驗研究

交通載具是目前地球耗損能源的主要原因，若能有效降低各式運動載具之阻力，將可減低能源的耗損及改善載具之操控特性，因此本研究針對表面塗裝及微氣泡減阻技術應用在水中載具表面摩擦阻力之抑制，作系統地深入探討，期能有效降低載具運動阻力，提升載具操縱性能，並減少能源之使用。實驗主要分成兩種不同減阻技術進行，一為表面塗裝減阻，另一為微氣泡減阻。表面塗裝減阻技術具有簡便的施工方式，可在載具表面直接施工，不需改變載具外形結構，是其最大優點；而微氣泡減阻技術則是有較高的減阻效能及可長時間使用的優勢，但載具外形結構之微氣泡產生裝置，設計安裝較為不易。在表面塗裝減阻實驗中，水下潛體模型運動雷諾數在Re=0.74E6~2.81E6範圍內，疏水性減阻塗料表現較優於親水性減阻塗料，當潛體運動速度更高時，親水性的塗料應該會有很好的減阻效果。當微氣泡供應量過大時，微氣泡會產生堆疊效應，使得微氣泡相互結合成大尺寸氣膜，此時雖然還有減阻效果，但在此過渡時期，減阻效率會有下滑趨勢。在垂直循環水洞實驗結果裡，當1μm多孔介質在7m/s流速狀態下，CV值為0.056時有最佳的減阻效率26﹪；而10μm多孔介質在相同流速狀態下，減阻效率約有23﹪。水面船模試驗在CV值約於0.16時，可視為臨界情況，CV值大於0.16後減阻效率趨於平緩，甚至在過大之空氣注入時，反而會有增加阻力現象發生，研究結果發現，微氣泡覆蓋區域愈大，船模表面有效減阻區域增加，由前、後段同時供氣最佳減阻效率約30 % 。

關鍵字

微氣泡. ；疏水性；親水性；減阻技術，摩擦阻力；塗裝

並列摘要

Currently, the vehicles are some of the major sources for the Earth energy consumption. It might decrease the energy loss in case it is available to reduce the drag of various vehicles. In the study, the drag reduction by coatings and micro bubbles which are applied to marine vehicles may result in an increase of the operating capability. The experiment is proceeded with two kinds of drag reducing techniques. The drag reduction by coatings on the surface is the simplest way since it has no need to change the original design. The micro bubbles drag reduction methodology can not only be used for an extended period of time but it also has high efficacy. The micro bubble generation system for vehicle structure is very complicated as far as the system’s design and fabrication are concerned. In the drag reduction by coatings study, the range of Reynolds number for the submerged body model is 0.74E6~2.81E6. The feature of drag reduction of hydrophobic coatings is better than hydrophilic coatings for the range of Reynolds number measured. Drag reduction for hydrophilic coatings is enhanced as the speed of submerged body is increased very fast. Whenever the micro bubbles are over by supplied, there will pile-up effect happened which makes micro bubbles to coagulate each other as a large size air film. Although they still has the drag reduction effect, but the efficiency of drag reduction drops at this transition period. In the experiment of vertical type circulating water tunnel, when 1μm porous medium is at 7m/s flow speed, the CV value defined as the ratio of the air injection rate to the sum of the air injection rate and the liquid injection rate at 0.056 has the best drag reduction efficiency of 26%. While 10μm porous medium is at the same flow speed, the drag reduction efficiency is only around 23%. When the CV value is around 0.16 during surface ship mode experiment, it can be treated as a critical condition. When CV value is larger than 0.16, its drag reduction efficiency stays relatively flat. Even it will increase the resistance whenever there has over by massive air injection. In the present study, we have found that the larger the area of region covered with micro bubbles, the higher the efficacy of drag reduction. Of the air is injected simultaneously from both the front and rear ends, then the best drag reduction efficiency is around 30%.

並列關鍵字

Hydrophilic ； Hydrophobic ； Coating ； Drag Reduction Technique ； Micro Bubbles. ； Skin Friction

參考文獻

2.Wang, J. j., Lan, S. l. and Chen, G., “Experimental Study on the Turbulent Boundary Layer Flow over Riblets Surface,” Fluid Dynamics Research, Vol. 27, 2000, pp. 217-229.

3.Walsh, M. J., “Turbulent Boundary Layer Drag Reduction Using Riblets,” AIAA paper, 1982-0169.

4.Hwang, D. P., “A Proof of Concept Experiment for Reducing Skin Friction by Using a Micro-Blowing Technique,” NASA Technical Memorandum 107315, AIAA paper, 1997-0546.

5.Hwang, D. P. and Biesiadny, T. J., “Experimental Evaluation of the Penalty Associated with Micro-Blowing for Reducing Skin Friction,” AIAA paper, 1997-0677.

6.Kodama, Y., Kakugawa, A., Takahashi, T., Nagaya, S. and Kawamura, T., “Drag Reduction of Ships by Microbubbles,” National Maritime Research Institute of Japan.

國際替代計量

水中載具減阻技術之實驗研究

全文下載

主題瀏覽