雙層流體中冰脊拖曳系數(shù)的實驗研究
發(fā)布時間：2019-04-23 11:48
【摘要】：全球氣溫升高在北極地區(qū)被放大,稱為“北極放大”現(xiàn)象。北極海冰在過去幾十年內發(fā)生了前所未有的快速變化,導致海冰范圍和厚度的持續(xù)衰減,在本世紀中頁就有可能出現(xiàn)夏季無冰的北冰洋。北極海冰的快速變化對北半球乃至我國的天氣和氣候造成了越來越顯著的影響,而且使得北極航道的開通成為可能,而成為各國政府關注的焦點。作為目前海冰研究的重要手段,數(shù)值模擬對北極海冰的快速變化仍然模擬得不夠準確,說明對海冰的關鍵物理過程仍缺乏深入理解。海冰拖曳系數(shù)是海冰動力學模型中的重要參數(shù),對于研究冰.水動力作用過程至關重要。為了完善冰.水拖曳系數(shù)的參數(shù)化方案,同時考慮到現(xiàn)場觀測中對冰.水界面的動力過程進行觀測的困難程度,本文針對冰.水界面上的冰脊形拖曳力和拖曳系數(shù)開展了實驗室物理模擬實驗研究。首先,目前海冰拖曳系數(shù)參數(shù)化的研究多針對于均勻流體,沒有考慮海洋分層的情況,而北極夏季海冰邊緣區(qū)內的海水鹽度躍層由于海冰融化的影響一般出現(xiàn)在較淺的位置,有可能對浮冰或者冰脊的運動造成影響。因此,為改進冰.水界面的海冰拖曳系數(shù)的參數(shù)化方案,在實驗室原有水槽的基礎上進行了設備改造,建立了分層流體模擬系統(tǒng),包括鹽水注入系統(tǒng),拖曳力測量系統(tǒng),運動平臺系統(tǒng),配重系統(tǒng)等。為分層流體實驗的開展奠定了基礎。其次,作為對比實驗,開展了單層流體中的冰脊拖曳力測量,考慮了6種不同形狀的冰脊模型在5種入水深度與12種水流流速下所受拖曳力的變化。分析說明單層流體中冰脊拖曳力隨著冰脊底角、水流流速和冰脊入水深度的增大而增大,冰脊所受拖曳力與速度的平方存在良好的線性關系,這一結論驗證了拖曳力理論公式。對拖曳系數(shù)的分析結果說明,單層流體中冰脊拖曳系數(shù)隨著水流流速的增大基本保持不變,隨著冰脊入水深度的增大而緩慢增大且增幅較小,隨著冰脊底角的變大而顯著變大。冰脊底角是影響單層流體中冰脊拖曳系數(shù)的主要因素。最后,與單層流體的實驗組次一致進行了雙層流體中的冰脊形拖曳力實驗。結果顯示,雙層流體中的冰脊拖曳力與單層流體中的變化規(guī)律存在明顯區(qū)別,當弗洛德數(shù)處于1-2區(qū)間時,雙層流體中的冰脊拖曳力呈現(xiàn)先增加后減小的趨勢；當弗洛德數(shù)大于2之后,雙層流體中的冰脊拖曳力與單層流體中的對應值基本一致,這主要是由于界面內波的影響造成的。而拖曳系數(shù)變化過程也較單層流體的情況存在差別,除了冰脊傾角的影響外,弗洛德數(shù)對雙層流體中拖曳系數(shù)的影響也很明顯。在弗洛德數(shù)較小(0.7)時,拖曳系數(shù)隨著弗洛德數(shù)增加迅速衰減,與冰脊角度無關；而在弗洛德數(shù)較大(0.7)時,拖曳系數(shù)隨著冰脊角度的增大而增大,與弗洛德數(shù)無關。因此采用分段擬合的方式得到雙層流體中冰脊拖曳系數(shù)的參數(shù)化關系。
[Abstract]:Global warming is magnified in the Arctic, known as the Arctic magnification. Arctic sea ice has undergone unprecedented rapid changes over the past few decades, leading to a continuous decline in the extent and thickness of sea ice, with the possibility of a summer ice-free Arctic Ocean on the middle page of this century. The rapid change of Arctic sea ice has caused more and more significant effects on the weather and climate in the northern hemisphere and even in China, and has made it possible to open the Arctic waterway, which has become the focus of attention of the governments all over the world. As an important means of sea ice research, numerical simulation is still not accurate enough to simulate the rapid change of Arctic sea ice, which shows that the key physical process of sea ice is still lack of in-depth understanding. The drag coefficient of sea ice is an important parameter in the dynamic model of sea ice. The hydrodynamic process is essential. To perfect the ice. Water drag coefficient parameterization scheme, taking into account in-situ observations of ice. This paper deals with the difficulty of observing the dynamic process of water interface. The drag force and drag coefficient of ice ridge on water interface are studied by physical simulation in laboratory. First of all, the current research on the parameterization of sea ice drag coefficient does not take account of ocean stratification for homogeneous fluids. However, the saliniferous leaps in the Arctic summer sea ice edge region generally appear in a shallow position due to the effect of sea ice melting. It may have an impact on the movement of ice floes or ice ridges. Therefore, in order to improve ice. The parameterization scheme of the sea ice drag coefficient of the water interface has been reformed on the basis of the original flume in the laboratory, and the layered fluid simulation system has been established, including the saline injection system, the towing force measurement system and the motion platform system. Weighing system, etc. It lays a foundation for the development of stratified fluid experiments. Secondly, as a comparative experiment, the drag forces of ice ridges in single-layer fluids are measured, and the variation of drag forces of six ice ridges with different shapes under 5 inlet depths and 12 flow velocities is taken into account. The analysis shows that the drag force of ice ridge in single layer fluid increases with the increase of the bottom angle of the ice ridge, the velocity of flow and the depth of water entering into the ice ridge. There is a good linear relationship between the drag force and the square of the velocity on the ice ridge. This conclusion verifies the theoretical formula of the drag force. The analysis results of the drag coefficient show that the drag coefficient of ice ridge in single layer fluid remains unchanged with the increase of flow velocity, increases slowly with the increase of water depth of the ice ridge, and increases significantly with the increase of the bottom angle of the ice ridge. The bottom angle of ice ridge is the main factor that affects the drag coefficient of ice ridge in single layer fluid. Finally, the ice ridge drag force experiment in the double layer fluid is carried out in accordance with the experimental group of the single layer fluid. The results show that the drag force of ice ridge in the double layer fluid is obviously different from that in the single layer fluid. When the Froude number is in the range of 1 ~ 2, the drag force of the ice ridge in the double layer fluid increases first and then decreases. When the Froude number is greater than 2, the drag force of the ice ridge in the double layer fluid is basically consistent with the corresponding value in the single layer fluid, which is mainly due to the influence of the internal wave at the interface. In addition to the dip angle of the ice ridge, the influence of Froude number on the drag coefficient in the double layer fluid is also obvious. When the Froude number is small (0.7), the drag coefficient decreases rapidly with the increase of the Froude number, independent of the angle of the ice ridge. When the Froude number is larger (0.7), the drag coefficient increases with the increase of the angle of the ice ridge, independent of the Froude number. Therefore, the parameterized relation of the drag coefficient of ice ridges in two-layer fluid is obtained by means of piecewise fitting.
【學位授予單位】：大連理工大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：P731.15
本文編號：2463436
[Abstract]:Global warming is magnified in the Arctic, known as the Arctic magnification. Arctic sea ice has undergone unprecedented rapid changes over the past few decades, leading to a continuous decline in the extent and thickness of sea ice, with the possibility of a summer ice-free Arctic Ocean on the middle page of this century. The rapid change of Arctic sea ice has caused more and more significant effects on the weather and climate in the northern hemisphere and even in China, and has made it possible to open the Arctic waterway, which has become the focus of attention of the governments all over the world. As an important means of sea ice research, numerical simulation is still not accurate enough to simulate the rapid change of Arctic sea ice, which shows that the key physical process of sea ice is still lack of in-depth understanding. The drag coefficient of sea ice is an important parameter in the dynamic model of sea ice. The hydrodynamic process is essential. To perfect the ice. Water drag coefficient parameterization scheme, taking into account in-situ observations of ice. This paper deals with the difficulty of observing the dynamic process of water interface. The drag force and drag coefficient of ice ridge on water interface are studied by physical simulation in laboratory. First of all, the current research on the parameterization of sea ice drag coefficient does not take account of ocean stratification for homogeneous fluids. However, the saliniferous leaps in the Arctic summer sea ice edge region generally appear in a shallow position due to the effect of sea ice melting. It may have an impact on the movement of ice floes or ice ridges. Therefore, in order to improve ice. The parameterization scheme of the sea ice drag coefficient of the water interface has been reformed on the basis of the original flume in the laboratory, and the layered fluid simulation system has been established, including the saline injection system, the towing force measurement system and the motion platform system. Weighing system, etc. It lays a foundation for the development of stratified fluid experiments. Secondly, as a comparative experiment, the drag forces of ice ridges in single-layer fluids are measured, and the variation of drag forces of six ice ridges with different shapes under 5 inlet depths and 12 flow velocities is taken into account. The analysis shows that the drag force of ice ridge in single layer fluid increases with the increase of the bottom angle of the ice ridge, the velocity of flow and the depth of water entering into the ice ridge. There is a good linear relationship between the drag force and the square of the velocity on the ice ridge. This conclusion verifies the theoretical formula of the drag force. The analysis results of the drag coefficient show that the drag coefficient of ice ridge in single layer fluid remains unchanged with the increase of flow velocity, increases slowly with the increase of water depth of the ice ridge, and increases significantly with the increase of the bottom angle of the ice ridge. The bottom angle of ice ridge is the main factor that affects the drag coefficient of ice ridge in single layer fluid. Finally, the ice ridge drag force experiment in the double layer fluid is carried out in accordance with the experimental group of the single layer fluid. The results show that the drag force of ice ridge in the double layer fluid is obviously different from that in the single layer fluid. When the Froude number is in the range of 1 ~ 2, the drag force of the ice ridge in the double layer fluid increases first and then decreases. When the Froude number is greater than 2, the drag force of the ice ridge in the double layer fluid is basically consistent with the corresponding value in the single layer fluid, which is mainly due to the influence of the internal wave at the interface. In addition to the dip angle of the ice ridge, the influence of Froude number on the drag coefficient in the double layer fluid is also obvious. When the Froude number is small (0.7), the drag coefficient decreases rapidly with the increase of the Froude number, independent of the angle of the ice ridge. When the Froude number is larger (0.7), the drag coefficient increases with the increase of the angle of the ice ridge, independent of the Froude number. Therefore, the parameterized relation of the drag coefficient of ice ridges in two-layer fluid is obtained by means of piecewise fitting.
【學位授予單位】：大連理工大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：P731.15
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