内波射线的传播与内孤立波过周期地形能量损耗的实验研究
发布时间：2018-08-24 16:08
【摘要】：海洋内波是海水密度稳定层结的海洋中普遍存在的现象，是海洋中大尺度能量级向小尺度能量级传递的中间过程，内波的传播演化具有研究意义。内波的实验室研究可以整体全面的把握住内波生成、演化的过程，同时可对理论研究与数值研究的结果进行验证，而且实验室研究具有可重复性，相比海洋观测而言资金投入少。 内波的实验室研究之前需要制备密度层结的流体，，对于内潮的实验需要在连续层结的流体中进行。密度连续分层的流体通常采用双缸法制备。采用传统的双缸法只能制备密度均匀层结的流体，而实际海水的密度剖面是具有跃层形式的。为了研究内波在非均匀层结下的传播特性，作者改进了传统的双缸法，从而可以制备出任意密度剖面的层结流体。经实验验证这种改进后的双缸法具有可行性。 作者通过采用这种方法研究了内波在不同密度层结下内波射线的传播现象。采用PIV技术对内波射线的流场进行观测，采用合成纹影技术对内波流体的密度扰动进行观测。由线性内波理论可知内波群速与相速方向相互垂直，结合实验结果，可知实验结果中的射线即为内波群速方向。根据内波生成源（振荡圆柱）的振荡频率与流体的浮性频率N计算得到的群速与水平方向的理论夹角，与实验结果的所测得的角度进行比较，发现两个角度非常接近，说明线性理论在本次实验的条件下是适用的。在三层线性分层实验中，内波射线在不同层的界面处发生折射现象，同时在界面处也会发生内波射线的反射现象。当内波圆频率介于上下层的浮性频率与中间层的浮性频率之间时，内波射线只在中间层传播。向上向下传播的两条射线相互作用在第二次反射的位置处形成了一个涡旋，此涡旋不断地生成、移动并消失。 作者在水槽中加入斜坡地形，研究内波射线遇到斜坡地形后的反射。实验中发现在本次实验设置的情况下，内波射线在反射后其宽度变窄。由于反射后的射线能量聚焦，内波的能量损耗较强。 在测量内孤立波过地形后能量损耗的实验中，作者推导得到在实验室情况下计算内孤立波动能和有效势能的方法，并通过实验测量了内孤立波通过周期地形后的能量损耗率与其振幅之间大致呈线性关系。
[Abstract]:Ocean internal wave is a common phenomenon in the ocean with stable sea density. It is an intermediate process between large scale energy level and small scale energy level. The propagation and evolution of internal wave is of great significance. The laboratory study of internal wave can grasp the process of internal wave generation and evolution, and verify the results of theoretical and numerical research, and the laboratory research is repeatable. Less money is invested than ocean observation. It is necessary to prepare dense stratified fluid before the laboratory study of internal wave, and the experiment of internal tide should be carried out in the fluid of continuous stratification. Fluid with continuous density stratification is usually prepared by two-cylinder method. The conventional two-cylinder method can only produce homogeneous stratified fluid with density, while the density profile of the actual seawater is in the form of cline. In order to study the propagation characteristics of internal waves in non-uniform layers, the author has improved the traditional two-cylinder method, thus the stratified fluid with arbitrary density profile can be prepared. The experimental results show that the improved two-cylinder method is feasible. By using this method, the phenomenon of internal wave ray propagation under different density layers is studied. The PIV technique is used to observe the internal wave ray flow field and the synthetic schlieren technique is used to observe the density disturbance of the internal wave fluid. The linear internal wave theory shows that the direction of group velocity and phase velocity are perpendicular to each other. Combined with the experimental results, the ray in the experimental results is known as the direction of group velocity of internal wave. According to the theoretical angle of group velocity and horizontal direction calculated from the oscillating frequency of the internal wave generator (oscillating cylinder) and the floating frequency of the fluid, it is found that the two angles are very close to each other. It shows that the linear theory is applicable under the condition of this experiment. In the three-layer linear delamination experiment, the internal wave ray refraction occurs at the interface of different layers, and the reflection of the internal wave ray also occurs at the interface. When the frequency of the inner wave circle is between the floating frequency of the upper and lower layer and the floating frequency of the middle layer, the internal wave ray propagates only in the middle layer. The interaction of two rays propagating upward and downward forms a vortex at the position of the second reflection, which continuously generates, moves and disappears. In this paper, slope topography is added to the flume to study the reflection of internal wave rays upon the slope topography. It is found in the experiment that the width of the internal wave ray becomes narrower after reflection. The energy loss of the internal wave is stronger because of the reflected ray energy focusing. In the experiment of measuring the internal solitary wave energy loss after crossing the terrain, the author derives the method of calculating the internal solitary wave energy and the effective potential energy in the laboratory case. The linear relationship between the energy loss rate and the amplitude of the internal solitary wave after passing through the periodic terrain is measured experimentally.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P731.24
本文编号：2201330
[Abstract]:Ocean internal wave is a common phenomenon in the ocean with stable sea density. It is an intermediate process between large scale energy level and small scale energy level. The propagation and evolution of internal wave is of great significance. The laboratory study of internal wave can grasp the process of internal wave generation and evolution, and verify the results of theoretical and numerical research, and the laboratory research is repeatable. Less money is invested than ocean observation. It is necessary to prepare dense stratified fluid before the laboratory study of internal wave, and the experiment of internal tide should be carried out in the fluid of continuous stratification. Fluid with continuous density stratification is usually prepared by two-cylinder method. The conventional two-cylinder method can only produce homogeneous stratified fluid with density, while the density profile of the actual seawater is in the form of cline. In order to study the propagation characteristics of internal waves in non-uniform layers, the author has improved the traditional two-cylinder method, thus the stratified fluid with arbitrary density profile can be prepared. The experimental results show that the improved two-cylinder method is feasible. By using this method, the phenomenon of internal wave ray propagation under different density layers is studied. The PIV technique is used to observe the internal wave ray flow field and the synthetic schlieren technique is used to observe the density disturbance of the internal wave fluid. The linear internal wave theory shows that the direction of group velocity and phase velocity are perpendicular to each other. Combined with the experimental results, the ray in the experimental results is known as the direction of group velocity of internal wave. According to the theoretical angle of group velocity and horizontal direction calculated from the oscillating frequency of the internal wave generator (oscillating cylinder) and the floating frequency of the fluid, it is found that the two angles are very close to each other. It shows that the linear theory is applicable under the condition of this experiment. In the three-layer linear delamination experiment, the internal wave ray refraction occurs at the interface of different layers, and the reflection of the internal wave ray also occurs at the interface. When the frequency of the inner wave circle is between the floating frequency of the upper and lower layer and the floating frequency of the middle layer, the internal wave ray propagates only in the middle layer. The interaction of two rays propagating upward and downward forms a vortex at the position of the second reflection, which continuously generates, moves and disappears. In this paper, slope topography is added to the flume to study the reflection of internal wave rays upon the slope topography. It is found in the experiment that the width of the internal wave ray becomes narrower after reflection. The energy loss of the internal wave is stronger because of the reflected ray energy focusing. In the experiment of measuring the internal solitary wave energy loss after crossing the terrain, the author derives the method of calculating the internal solitary wave energy and the effective potential energy in the laboratory case. The linear relationship between the energy loss rate and the amplitude of the internal solitary wave after passing through the periodic terrain is measured experimentally.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P731.24
【参考文献】
相关期刊论文 前1条
1 席华;氯化钠溶液物性关系式[J];天津轻工业学院学报;1997年02期
本文编号：2201330
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