本文選題：沿海聲層析 + 流場反演　； 參考：《浙江大學(xué)》2017年博士論文

【摘要】：沿海聲層析(Coastal Acoustic Tomography,簡稱CAT)技術(shù)相比傳統(tǒng)的測流方法,它僅在觀測區(qū)域外圍布置較少的站位即可對近岸快速變化的潮流實現(xiàn)大面積、長時間的同步觀測。CAT適用于海灣、海峽和港口等航運繁忙、漁業(yè)活動頻繁的近岸半封閉海區(qū)。CAT觀測在站位選取、流場反演等方面仍有許多需要研究和改進(jìn)的地方。本論文基于逆方法和數(shù)據(jù)同化方法對CAT的數(shù)據(jù)進(jìn)行流場反演,并選取了三個典型的近岸海區(qū)(三門灣、舟山和瓊州海峽)對潮流結(jié)構(gòu)、余流動力機(jī)制等近海潮流動力學(xué)問題進(jìn)行了討論。論文用集合卡曼濾波方法將CAT數(shù)據(jù)同化到三角網(wǎng)格的海洋模式中。首先,我們建立了高空間分辨率三角網(wǎng)格,用于擬合近岸復(fù)雜的岸線邊界;其次,我們通過聲線與不規(guī)則網(wǎng)格的位置關(guān)系建立了傳播時間差與模式狀態(tài)向量在水平方向上的投影關(guān)系;最后,我們利用垂向平均的傳播時間差數(shù)據(jù)進(jìn)行數(shù)據(jù)同化,得到三維的流場結(jié)構(gòu)。論文利用三門灣CAT觀測數(shù)據(jù),實現(xiàn)了三角網(wǎng)格的CAT數(shù)據(jù)同化。數(shù)據(jù)同化方法得到了 CAT觀測區(qū)域內(nèi)部楊礁附近的精細(xì)流場結(jié)構(gòu)。數(shù)據(jù)同化方法得到的流場與三個定點ADCP的平均均方根誤差為0.07 m s-1,優(yōu)于逆方法(0.12 ms-1)和模式模擬(0.17 m s-1)的結(jié)果。數(shù)據(jù)同化方法得到了逆方法無法獲得的流速垂向結(jié)構(gòu),與ADCP在垂向各層的均方根誤差范圍為0.02 m s-1至0.14 ms-1,同樣優(yōu)于模式模擬的結(jié)果(0.08 m s-1至0.27 m s-1)。這些結(jié)果表明數(shù)據(jù)同化方法得到的流場精度最高。進(jìn)一步的敏感實驗結(jié)果則表明,數(shù)據(jù)同化方法在聲線數(shù)據(jù)缺失的情況下比逆方法更為穩(wěn)定,精度更高。由此可見,相比于逆方法和模式模擬,基于非結(jié)構(gòu)三角網(wǎng)格的CAT數(shù)據(jù)同化方法在近岸流場反演具有更好的效果。在對近岸非線性潮的研究中,我們利用連續(xù)27小時的15分鐘滑動平均的舟山峙頭洋灣的CAT數(shù)據(jù),用逆方法反演得到了觀測區(qū)域的主要的半日潮(M2)以及由M2產(chǎn)生的非線性潮M4和M6的潮流的水平結(jié)構(gòu)。三者的空間平均的流速振幅比為M2:M4:M6=1.00:0.15:0.11。我們將M2的潮流代入到淺水方程的平流項和底摩擦項,通過理論推導(dǎo)計算得到了理論上M4和M6的潮流。對比觀測和理論推導(dǎo)的結(jié)果,在水深大于60 m的深水區(qū)域,M4與平流項產(chǎn)生的潮流非常接近,表明峙頭洋灣深水區(qū)域的M4主要由平流項作用產(chǎn)生。而對M6的研究則表明,M6在水深小于20 m的區(qū)域主要由底摩擦項的作用產(chǎn)生。我們還討論了 M4和M6對峙頭洋灣的潮流不對稱性變形的影響,發(fā)現(xiàn)M4在觀測區(qū)域?qū)Τ绷鞯牟粚ΨQ性變形的影響大于M6。我們還利用一個M2周期內(nèi)的動量方程對峙頭洋灣的余流動力機(jī)制進(jìn)行了討論。結(jié)果表明,余水位的壓力梯度項和余流的平流項占了潮流的平流項的75%,所以峙頭洋灣的余流是由潮流的非線性作用所產(chǎn)生的。在瓊州海峽為期15天的CAT觀測實驗中,我們利用CAT同步觀測數(shù)據(jù)得到了潮流和余流的水平分布,并計算了通過瓊州海峽的流量。結(jié)果顯示,瓊州海峽以全日潮為主,O1、K1、M2、S2和MSF五個分潮的流速振幅比為1.00:0.60:0.47:0.21:0.11。余流在海峽北部為西向,在海峽南部轉(zhuǎn)為南向。余流流速在海峽北部區(qū)域較大,最大余流流速為西向12.4 cm/s。利用CAT數(shù)據(jù)估計的流量變化范圍為-0.71 Sv到0.86 Sv,余流流量為-0.04 Sv(西向為負(fù))。另外,對觀測區(qū)域的動量分析結(jié)果顯示,潮汐調(diào)整和海峽兩端入口處的水位差對維持西向余流起重要作用。本文利用CAT的觀測數(shù)據(jù),得到了近岸主要的全日潮(O1和K1)、半日潮(M2和S2)、非線性潮(M4和M6)和余流的空間結(jié)構(gòu),并討論了余流和非線性潮的動力機(jī)制。由此可見,CAT在近岸潮流的觀測上具有獨特的優(yōu)勢,可對潮流動力學(xué)研究發(fā)揮重要作用。
[Abstract]:Coastal Acoustic Tomography (abbreviated CAT) technology, compared with the traditional method of flow measurement, can achieve a large area of fast changing tidal current only in the periphery of the observation area. Long time synchronous observation of.CAT is applicable to the Bay, the Strait and the port and so on, and the close shore half closed to the frequent fishing activities. There are still many areas to be studied and improved in the.CAT observation of the sea area, such as site selection and flow field inversion. The inverse method and data assimilation method are used to invert the flow field of the CAT data, and three typical nearshore sea areas (Sanmen Bay, Zhoushan and Qiongzhou Strait) are selected for the tidal flow structure, the residual current dynamic mechanism and so on. In this paper, the problem of mechanics is discussed. In this paper, the CAT data is assimilated into the ocean model of triangular mesh by using the ensemble Kaman filter. First, we have established a high spatial resolution triangular mesh to fit the complex shoreline boundary of the near shore. Secondly, we establish the propagation time difference and mode through the relationship between the acoustic line and the irregular network lattice. In the end, we use the vertical average propagation time difference data to make data assimilation and get the three-dimensional flow field structure. In this paper, the CAT data assimilation of the triangular mesh is realized by using the CAT observation data of the Sanmen Bay. The data assimilation method gets the fine flow near the poplar reef within the CAT observation area. The mean square root error between the flow field and the three fixed-point ADCP is 0.07 m s-1, which is better than the inverse method (0.12 MS-1) and the model simulation (0.17 m s-1). The data assimilation method obtains the vertical structure of the flow velocity that the inverse method can't obtain, and the mean square root error range of the ADCP in the vertical layers is 0.02 m s-1 to 0.14. MS-1 is also better than the result of model simulation (0.08 m s-1 to 0.27 m s-1). These results show that the data assimilation method has the highest precision of flow field. Further sensitive experimental results show that the data assimilation method is more stable and more accurate than the inverse method in the absence of acoustic line data. Simulation, CAT data assimilation based on unstructured triangular mesh has a better effect on inshore flow field inversion. In the study of near shore nonlinear tide, we use inverse method to retrieve the main semidiurnal tide (M2) of the observational region and the M2 produced by inverse method by using the CAT data of the Zhoushan Shi tou Bay, Zhoushan. The horizontal structure of the flow of the nonlinear tidal M4 and M6. The spatial average velocity amplitude ratio of the three is M2:M4:M6=1.00:0.15:0.11.. We substituting the flow of M2 into the advection term and the bottom friction term of the shallow water equation. The theoretical derivation is used to calculate the tidal currents of M4 and M6 in theory. The results of comparison and theoretical derivation are more than 60 in water depth. In the deep water area of M, M4 is very close to the flow generated by the advection term, indicating that the M4 in the deepwater area of the bay is mainly produced by the effect of advection. The study of M6 shows that M6 is mainly produced by the bottom friction term in the area less than 20 m in depth. We also discuss the influence of M4 and M6 on the asymmetrical deformation of the tidal current in the bay. It is found that the influence of M4 on the asymmetrical deformation of the tidal current is greater than M6.. We also use the momentum equation in a M2 period to discuss the dynamic mechanism of the residual current in the bay. The results show that the pressure gradient term of the residual water level and the advection term of the residual current account for 75% of the current advection term, so the residual current in the bay of Shi tou ocean is a tide. In the 15 day CAT observation experiment of the Qiongzhou Strait, we use the CAT synchronous observation data to obtain the horizontal distribution of the flow and residual flow, and calculate the flow through the Qiongzhou Strait. The results show that the Qiongzhou Strait is dominated by the full day tide, and the velocity and amplitude ratio of the five tides of O1, K1, M2, S2 and MSF is 1.00:0.60:. The 0.47:0.21:0.11. residual current is westward in the north of the Strait and southward in the south of the Strait. The residual current flow velocity is larger in the north of the Strait. The maximum flow velocity is 12.4 cm/s. West to 0.86 Sv using CAT data. The residual flow is -0.04 Sv (West to negative). In addition, the momentum analysis results of the observed area show the result of the momentum analysis. It is shown that the tidal adjustment and the water level difference at the entrance to the two ends of the Strait play an important role in maintaining the westward residual current. In this paper, we use the observation data of CAT to obtain the spatial structure of the main total diurnal tides (O1 and K1), semidiurnal tides (M2 and S2), nonlinear tides (M4 and M6) and residual currents in the near shore, and discuss the dynamic mechanism of the residual and nonlinear tides. Thus, it can be seen that CAT is in the near future. Shore tide observation has unique advantages and can play an important role in the study of tidal dynamics.

【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：P714.1

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本文編號：1814628