本文選題：蒙特利峽谷 + 底邊界層　； 參考：《中國海洋大學》2014年碩士論文

【摘要】：海洋中存在各種尺度的運動,通常能量的傳遞都是從大尺度到小尺度,最后以湍流運動的形式耗散。湍流是不同于層流且漫無規(guī)則的小尺度混亂運動,廣泛存在于大氣、海洋和工程技術(shù)等領(lǐng)域的流體運動中。湍流結(jié)構(gòu)復雜多樣,在時問和空問上具有問歇性、隨機性、高渦度性、高非線性,在流體中產(chǎn)生強混合擴散效應。由于湍流的這些特殊性質(zhì),湍流很難直接觀測,缺乏大范圍、長時間的連續(xù)觀測資料,湍流的結(jié)構(gòu)、產(chǎn)生機制尚不清晰�；诤Ｑ罂茖W對湍流長期觀測的需要,本文利用2011年4月24日到10月25日期間,蒙特利峽谷底邊界層內(nèi)ADV連續(xù)觀測流速數(shù)據(jù),分析峽谷底邊界層內(nèi)流速變化規(guī)律,估算湍流特征量,分析湍流特征。 ADV實測的每分鐘平均流速數(shù)據(jù)分析表明,在蒙特利峽谷底邊界層內(nèi)存在很強的流動,平均流速可達0.398m/s。峽谷底部潮流屬于逆時針旋轉(zhuǎn)潮流系統(tǒng),具有半日周期和全日周期的變化特征,其中半日周期占主導。日平均的流速數(shù)據(jù)譜分析和小波分析結(jié)果表明,峽谷底部潮流在5月和8月存在近似15天和5天的顯著周期,6月、10月等時間段存在大約2-4天的顯著周期。蒙特利峽谷底邊界層內(nèi)流速日平均和月平均數(shù)據(jù)顯示,5月峽谷底部流速達到最大值,9月和10月流速變?nèi)酰凰椒较蛄鲃佣酁槲飨蚝湍舷蛄鲃?垂直方向長期存在著上升流；觀測期間4月到6月水平方向流動表現(xiàn)為南向流強于西向流,之后西向流速增大,超過南向流。 蒙特利峽谷底邊界層內(nèi),水流紊動特征表現(xiàn)為脈動速度分量一階矩近似符合高斯標準正態(tài)分布,剪切應力相關(guān)的二階協(xié)方差項分布表現(xiàn)為高鋒態(tài)正偏特征,湍流動能相關(guān)的二階方差項分布表現(xiàn)為高鋒態(tài)負偏特征。在流速最小時刻,利用w’和u'w'的時間自相關(guān)函數(shù)曲線的第二個峰值近似模擬出的湍流猝發(fā)周期分別為5.5s和3s；在流速最大時刻,模擬出的湍流猝發(fā)周期分別為2.5s和2s；流速中間時刻,自相關(guān)函數(shù)曲線無明顯的峰值。 湍流特征研究發(fā)現(xiàn),蒙特利峽谷底邊界層內(nèi)湍流存在明顯的各向異性。脈動強度的水平分量與垂直分量相差一個數(shù)量級；湍流摩擦速度和拖曳系數(shù)日平均的變化范圍是6.50×10-3-2.32×10m/s和6.30×10-3-4.36×10,月平均最小值發(fā)生在7月；湍流耗散率一個周日內(nèi)變化可達2-3個數(shù)量級,觀測期間變化范圍是1.09×108-6.62×10-5W/kg。底邊界層內(nèi)湍流特征量存在顯著的周期變化,在一個周日內(nèi)都以半日周期占優(yōu)；湍流脈動強度和耗散率存在全日周期和三分之一日周期,湍流耗散率還表現(xiàn)出四分之一日周期特征；摩擦速度和拖曳系數(shù)存在全日周期和四分之一日周期。脈動強度、摩擦速度和拖曳系數(shù)都表現(xiàn)出大約8天和4天的顯著周期。利用估算的湍流耗散率ε、摩擦速度u*和湍流動能et對理論模型ε-u*和ε-et進行檢驗,結(jié)果表明其理論模型不完全適用于蒙特利峽谷底邊界層,模型理論系數(shù)大約為實測資料所得的修正系數(shù)的10倍。
[Abstract]:The movement of various scales exists in the ocean. The transfer of energy is usually from the large scale to the small scale, and finally dissipated in the form of turbulent motion. Turbulence is a small scale chaos movement which is different from laminar flow and irregularity. It is widely found in the fluid movement in the fields of atmosphere, ocean and engineering. Turbulent structure is complex and varied. There is a strong mixed diffusion effect in the fluid. Because of these special properties of turbulence, turbulence is difficult to observe directly, lack of large range, long time continuous observation data, the structure of turbulence, and the mechanism of production is not clear. Based on the need of ocean science for the long-term observation of turbulence, In this paper, the flow velocity data in the bottom boundary layer of Monterey gorge is continuously observed from April 24, 2011 to October 25th. The flow velocity changes in the boundary layer at the bottom of the canyon are analyzed, the characteristics of the turbulence are estimated and the characteristics of the turbulence are analyzed.
The analysis of average velocity of velocity per minute measured by ADV shows that there is a strong flow in the bottom boundary layer of Monterey gorge, and the average flow rate can reach the bottom of 0.398m/s. Canyon, which belongs to the reverse clockwise rotation flow system, which has the characteristics of the semidiurnal and the whole daily cycle. The results of the wavelet analysis show that the flow of the bottom of the valley has a significant period of approximately 15 days and 5 days in May and August, and there is a significant period of about 2-4 days in June and October. The daily and monthly mean velocity of flow velocity in the bottom boundary layer of Monterey Gorge shows that the flow velocity at the bottom of the May Canyon reaches the maximum, and the velocity in September and October is weaker; water square is square. The flow in the direction of flow is mostly westward and southward, and there is an upward flow in the vertical direction for a long time. During the observation period from April to June, the flow in the horizontal direction is stronger than the westward flow, and then the westward flow velocity increases, exceeding the south flow.
In the bottom boundary layer of the Monterey gorge Valley, the turbulent flow characteristics show that the first order moment of the pulsating velocity component approximates the Gauss standard normal distribution. The two order covariance distribution related to the shear stress is characterized by the positive bias of the high front state, and the two order variance distribution related to the turbulent kinetic energy is characterized by the negative bias of the high front state. The second peaks of the time autocorrelation function curve of W 'and u'w' approximated the turbulent burst periods of 5.5s and 3S, respectively. At the maximum velocity, the simulated turbulent burst periods were 2.5s and 2s, respectively, and there was no obvious peak in the autocorrelation function curve at the middle time of flow velocity.
It is found that there is an obvious anisotropy in the turbulent flow in the bottom boundary layer of the Monterey gorge. The horizontal and vertical components of the pulsating intensity vary by one order of magnitude; the daily average variation range of the turbulent friction velocity and drag coefficient is 6.50 * 10-3-2.32 * 10m/s and 6.30 x 10-3-4.36 x 10, and the monthly mean minimum occurs in July; The flow dissipation rate can be changed to 2-3 orders of magnitude in one Sunday. The variation range of the observation period is a significant periodic variation in the turbulent characteristics in the bottom boundary layer of 1.09 x 108-6.62 x, which is dominant in a half day period in a Sunday. The turbulent fluctuation intensity and dissipation rate are all daily and 1/3 days, and the dissipation rate of turbulent flow is found. The 1/4 day periodic characteristics are also shown; the friction velocity and drag coefficient exist full day period and 1/4 day period. The pulsation strength, friction velocity and drag coefficient show a significant period of about 8 days and 4 days. The estimated turbulence dissipation rate, friction velocity u* and turbulent flow energy et are examined for the theoretical model epsilon -u* and epsilon -et The results show that the theoretical model is not entirely applicable to the bottom boundary layer of Monterey gorge, and the theoretical coefficient of the model is about 10 times that of the measured data.
【學位授予單位】：中國海洋大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：P731.26

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