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題名 | Hydrodynamic Characteristics of Double-Plate Saucer-Shaped Otter Board=雙片圓型網板之力學特性 |
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作者姓名(中文) | 林俊辰; 蘇偉成; 王敏昌; 周耀烋; | 書刊名 | 臺灣水產學會刊 |
卷期 | 22:3 1995.09[民84.09] |
頁次 | 頁191-201 |
分類號 | 439.3 |
關鍵詞 | 雙片圓型網板; 展抗比; 壓力中心係數; 攻角; 展開性能; Double-plate saucer-shaped otter boards; Sheer-drag ratio; Coefficient of Pressure centre; Angle of attack; Spreading characteristics; |
語文 | 英文(English) |
中文摘要 | 單艘拖網船為捕撈漁場中淺水層之魚群,作業時必須縮短曳網之長度,但網板之展開距離將因此而縮小,網口之展開亦會隨之變形而影響魚群入網,使漁獲效率降低。為突破此項瓶頸,則必須於短曳綱之情況下使網板仍能維持原有之展開,又圓型網板之展開及浮升性能均較V型網板為佳,極適於作為中層拖網使用。因此,本研究乃製作由雙片鐵板構成之圓型網板,期能增網板之展開性能,其彎曲度為10%,縮小比例為1:6,網板直徑為30.7 cm,調整網板中之雙片鐵板的間距為0.43, 0.51, 0.60, 0.68, 0.78 (�隉G網板直徑),利用國立成功大學造船系之環流水槽,進行試驗,將網板結附於L型支持棒之下方,而三分力計連結於支持棒的上方,變化流速範圍為0.3-1.0 m/s,攻角為0-40°,以瞭解雙片圓型網板在水中之力學特性。雙片與單片圓型網板之抗力係數比介於1.45-2.34之間,而以間距為0.60之雙片網板於攻角30°時,其比值最小;雙片與單片圓型網板之展開力係數比為1.74-3.69,而間距在0.60以上之雙片網板,其比值多大於2,亦即雙片網板之界面層不會產生剝離現象(Flow separation)。於攻角5-30°,間距為0.60�n�飫氻岑糷戇籅O的展抗比與單片網板之比值為最大。由圓型網板之展開力係數、最大展抗比時之攻角前後各5度範圍內的平均展抗比、最大展抗比之75%以上的攻角範圍大小及壓力中心之變異係數,來判定網板之展開特性、效能及穩定性,得知雙片圓型網板之力學特性優於單片圓型網板,且雙片圓型網板中之片與片的距離,以0.60較為適宜。 |
英文摘要 | To improve the technology of obtaining the horizontal spread between two otter boards as large as possible in the condition of short warps, the saucer-shaped otter board made of double plates is used in the research to enlarge its sheer force. The camber, scale and diameter of the otter board arc 10%, 1:6 and 307 mm respcctively. The intervals between two plates of the double-plate otter board are 0.43, 0.51, 0.60, and 0.78 (�� : diameter of otter board). The experiments were carried out in a flume tank cquipped at the Naval Architecture and Marine Engineering Department of National Cheng Kung University. The board model was fixed at the lower end of the supporting bar and the three-component load cell at the top end. The flow speed and angle of attack were changed from 0.3 to 1.0 m/s and from 0 to 40 degrees respectively to understand the hydrodynamic characteristics of the otter boards. The ratio of drag coefficient of the double-plate otter board to that of single-plate otter board is 1.45- 2.34. The ratio is the least at d/ of 0.60 when the angle of attack is within 30 degrees. The ratio of sheer coefficient of the double-plate otter board to that of single-plate otter board is 1.74-3.69. And this ratio, however, is greater than 2 when d/l is > 0.60 and the angle of attack is 30 degrees. That is to say, the sheer force of the double-plate otter board remained unaffected by the flow separation on boundary layer of otter board in these conditions. The rate of sheer-drag ratio of double-plate otter board to that of single-plate otter board is maximum at d/ of 0.60 and an attack angle between 5 and 30 degrees. The double-plate saucer-shaped otter boards are more effective than the single-plate boards in the operation of midwater trawling on considering the spreading characteristics, efficiency and stability of otter board. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。