劉倬騰臺灣大學：海洋研究所邱元玠Chiou, Yuan-JieYuan-JieChiou2007-11-272018-06-282007-11-272018-06-282007http://ntur.lib.ntu.edu.tw//handle/246246/56459當帶電的粒子在電磁場中運動時，會感受到電場與磁場的作用力，這個電磁力垂直於粒子的速度以及磁場方向。 因為海水中含有帶電離子，如鈉離子Na+ ，氯離子 Cl- …等，這些粒子隨著洋流在地球的磁場中流動時，這些帶電離子感受到電磁力，驅使正負電荷向相反方向移動，形成新的電流與電場。在有邊界的情況，正負離子累積在相反的邊界上，而造成電位差。此電位差跟洋流的流速與寬度有關，流速或者寬度越大，則電位差越大。因此，藉由量測橫過洋流兩端點的電位差，可以了解到洋流的流速變化，進而得到洋流的流量資訊。 台琉海底電纜(OKITAI Cable)位於台灣東北，連接宜蘭縣頭城鎮與日本沖繩縣那壩市。該電纜於1997年五月自商業運作中除役，不再供電與通訊。台灣大學與琉球大學自1998年六月開始紀錄經過該海底電纜所量測到台灣與那壩間的海水電位差，以研究此區域的黑潮流量變化。 最常用來描述電纜電壓的是ㄧ維平衡模式，它可以解釋大部分海流變化與電壓變化的相關性。但是，台琉海底電纜並非直接橫越黑潮就上岸，而是在下游400公里外上岸，電纜電壓與黑潮流量的關係複雜而且不明顯。一維平衡模式所推算的電纜電壓可以定性地解釋電纜電壓隨時間的變化，與潮流、黑潮、渦流等海洋現象變化的關係，但是其估算的電纜電壓值約為量測值的24倍。經建立包含分層海水及地殼導電的二維模式，增加下層海水漏電的效應，黑潮流軸位置的影響，以及黑潮左右海底地形的不對稱，終能模擬得到適當的電纜電壓值。When charged particles move in the magnetic field, they will experience an electromagnetic force called Lorentz force which is orthogonal to both the direction of velocity and magnetic field. Because sea water contains ions, and ions will be forced to different directions according to the sign of their charges. Therefore, these ions will generate voltage difference across the ocean current due to Lorentz force. The voltage difference strongly relates to the current. For example, periodical changes with tidal current, mean voltage is set up by mean current. The larger is the current velocity, the larger is the voltage difference across the current. So it’s possible to monitor current variation by measuring voltage difference. The OKITAI cable cross the Kuroshio near the entrance to East China Sea was retired from its commercial service in May 1997 and voltage difference between Toucheng and Naha was measured since June 1998. We may use this cable voltage to study the ocean phenomena in this area. The most common model to describe cable voltage is 1-dimensional model. It worked fine in estimating the Gulf Stream transport variation, the effect of tidal current and eddies, but the measured cable voltage that is induced by Kuroshio transport, is about 4% of that predicted by 1-D models. A 2-D model with conductive boundary and lower layer, inhomogeneous bathymetry and the flow structure of Kuroshio was developed. It shows that the cable voltage is insensitive to the conductivity of sediment, but sensitive to the distance of Kuroshio from Taiwan. The predicted cable voltage is about 70% of the measured values. Ancillary data (like sea level data from tide gauges and satellite altimeters) are needed for estimating respective contributions to cable voltage from Kuroshio, eddies, tidal current and noises.致謝 i 中文摘要 ii Abstract iii Contents iv Figure index vi Table index ix Symbols index x Important equation index xi Chapter 1 Introduction 1.1 Motivation 1 1.2 Review 4 Chapter 2 Observation and Data Analysis 2.1 Experiment Area and Measuring Instrument 9 2.2 What Make Cable Voltage Change? 11 2.3 Method of Data Analysis 13 2.4 Ocean Phenomena 2.4.1 High Frequency Motion 15 2.4.2 Low-Frequency Signals 17 2.4.3 Average Transport 20 Chapter 3 Model Simulation and Discussion 3.1 The 1-D Equilibrium Model 3.1.1 The 1-D Equilibrium Equation of Lorentz Force 21 3.1.2 Test of OSU Model 22 3.1.3 Tides Current Generated Voltage 23 3.1.4 Average Transport 26 3.1.5 Eddy and Meso-scale Variation 27 3.1.6 Result, Modification and Discussion 32 3.2 Capacitor Model and Phase Lag 3.2.1 Analytic Model 34 3.2.2 Results and Discussion of Capacitor Model 39 3.3 The 2-D Conductive Boundary Model 3.3.1 Model Building 40 3.3.2 Simulation Results and Discussion 3.3.2-1 Voltage vs. Boundaries 45 3.3.2-2 Voltage vs. Meander of Kuroshio 50 Chapter 4 Conclusion and Future Study 4.1 Conclusion 54 4.2 Future Study 56 References 58 Appendixes I Electric potential of line-source of charges 60 Appendixes II Electric potential at the line-source of charges 614523072 bytesapplication/pdfen-US海底電纜電壓量測黑潮數值模擬submarine cablevoltage measurementKuroshionumerical simulation[SDGs]SDG14thesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/56459/1/ntu-96-R93241107-1.pdf