本文選題：分層流體 + 內(nèi)波��； 參考：《中國(guó)海洋大學(xué)》2014年碩士論文

【摘要】：海洋內(nèi)波發(fā)生于密度分層的海洋中，因?yàn)樘?yáng)的熱輻射等因素造成海水密度分布在垂直方向上形成穩(wěn)定的層化特性，如果有擾動(dòng)發(fā)生在在密度穩(wěn)定層化海洋中，就有可能會(huì)導(dǎo)致在海水密度躍層處產(chǎn)生內(nèi)波。 由于內(nèi)波波幅大，波長(zhǎng)長(zhǎng)，內(nèi)部蘊(yùn)含能量巨大。內(nèi)波發(fā)生時(shí)，以密度分界面為邊界，在上下層形成的波致流方向相反，形成強(qiáng)烈剪切流。這種強(qiáng)烈的作用力作用在海底工程結(jié)構(gòu)物之上，會(huì)對(duì)其施工安裝和安全運(yùn)營(yíng)形成潛在威脅。并且內(nèi)波荷載在垂向分布正負(fù)交錯(cuò)，造成海底結(jié)構(gòu)物周期性振動(dòng)，加速其疲勞破壞。細(xì)長(zhǎng)圓柱體是組成海洋結(jié)構(gòu)物的基本構(gòu)件，本文針對(duì)內(nèi)波場(chǎng)中圓柱體進(jìn)行試驗(yàn)測(cè)量，研究其在內(nèi)波作用下的水平作用力及其影響因素。 首先，運(yùn)用莫里森方程結(jié)合mKdv方程估算模型在實(shí)驗(yàn)室內(nèi)波水槽所造內(nèi)波中的受力情況，根據(jù)對(duì)內(nèi)波作用力的粗略估算，選擇合適類型傳感器以及相應(yīng)的傳感器量程。由于測(cè)力傳感器在水下工作，受到浮力、水的粘滯作用以及其他因素的干擾，在空氣中進(jìn)行率定的傳感器不能真實(shí)反映電壓信號(hào)和圓柱體模型受力之間的關(guān)系，因此，傳感器的率定需要試驗(yàn)工況下進(jìn)行。在此基礎(chǔ)下，設(shè)計(jì)傳感器的率定系統(tǒng)以及內(nèi)波水平力的測(cè)量系統(tǒng)。 然后，設(shè)計(jì)試驗(yàn)工況，討論內(nèi)波波幅以及圓柱體所處深度和圓柱體模型直徑對(duì)其所受到的水平力的影響，共計(jì)二十七種工況，選擇三個(gè)測(cè)力傳感器。將選擇好的測(cè)力傳感器在試驗(yàn)條件下進(jìn)行水下率定，對(duì)所得到的的數(shù)據(jù)進(jìn)行擬合，得到傳感器輸出電壓信號(hào)和力的對(duì)應(yīng)關(guān)系。 最后，進(jìn)行內(nèi)波場(chǎng)中水平圓柱體的水平受力試驗(yàn)。得到的試驗(yàn)數(shù)據(jù)由于試驗(yàn)裝置振動(dòng)以及電磁干擾會(huì)有噪音，將試驗(yàn)數(shù)據(jù)進(jìn)行去噪處理后進(jìn)行時(shí)域分析，得到三個(gè)變量對(duì)圓柱體受力的影響關(guān)系。對(duì)內(nèi)波場(chǎng)中不同工況下圓柱體受力進(jìn)行分析得到圓柱體在內(nèi)波場(chǎng)中所受到水平作用沿深度的分布規(guī)律和圓柱體直徑以及內(nèi)波振幅對(duì)圓柱體模型所受水平作用力的影響規(guī)律。然后通過(guò)傅里葉變換，，得到圓柱體在內(nèi)波作用下的動(dòng)力響應(yīng)頻譜圖，發(fā)現(xiàn)內(nèi)波對(duì)圓柱體順流向作用力的頻率成分除了主頻外還存在一個(gè)兩倍于主頻的頻率成分，且圓柱體在主頻率處的響應(yīng)比在兩倍頻率處的響應(yīng)要大。
[Abstract]:Ocean internal waves occur in a density-stratified ocean because of factors such as solar thermal radiation, which result in a stable stratification of sea water density distribution in the vertical direction, if any disturbance occurs in a density-stable stratified ocean. It is possible to produce internal waves at the density cline of seawater. Because of the large amplitude of internal wave and long wavelength, the internal energy is huge. When the internal wave occurs, the density interface is taken as the boundary, the wave induced flow in the upper and lower layers is opposite, and the strong shear flow is formed. This kind of strong force acting on the structure of submarine engineering will pose a potential threat to its construction installation and safe operation. Moreover, the vertical distribution of internal wave loads is positively or negatively staggered, which results in periodic vibration of undersea structures and accelerates their fatigue failure. Thin and long cylinders are the basic components of ocean structures. In this paper, the horizontal forces and their influencing factors of cylinders in the internal wave field are studied. Firstly, the force of the internal wave produced by the laboratory wave tank is estimated by using the Morrison equation and mKdv equation. According to the rough estimation of the force acting on the internal wave, the appropriate type of sensor and the corresponding sensor range are selected. Because the force sensor works under water and is disturbed by buoyancy, water viscosity and other factors, the sensor with constant rate in the air can not truly reflect the relationship between the voltage signal and the stress of the cylinder model. The rate of the sensor needs to be tested. On this basis, the sensor rate determination system and the internal wave horizontal force measurement system are designed. Then, the effects of the amplitude of internal wave, the depth of the cylinder and the diameter of the cylinder model on the horizontal force are discussed. A total of 27 working conditions are designed and three force sensors are selected. The selected force sensor is used to determine the underwater rate under the experimental conditions, and the corresponding relationship between the output voltage signal and the force of the sensor is obtained by fitting the obtained data. Finally, the horizontal force test of the horizontal cylinder in the internal wave field is carried out. Due to the vibration of the test device and the noise caused by electromagnetic interference, the experimental data are analyzed in time domain after de-noising, and the influence of the three variables on the cylinder force is obtained. The distribution law of the horizontal action along the depth of the cylindrical wave field and the influence of the cylinder diameter and the amplitude of the internal wave on the horizontal force of the cylindrical model are obtained by analyzing the force of the cylinder under different working conditions in the internal wave field. Then, by Fourier transform, the dynamic response spectrum of the cylinder is obtained. It is found that the frequency component of the internal wave acting on the cylinder is two times the main frequency in addition to the main frequency. The response of the cylinder at the main frequency is larger than that at the double frequency.
【學(xué)位授予單位】：中國(guó)海洋大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：P731.22

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