本文選題：沿岸流　切入點(diǎn)：不穩(wěn)定　出處：《大連理工大學(xué)》2015年博士論文

【摘要】：目前對沿岸流的實(shí)驗(yàn)研究主要針對現(xiàn)場實(shí)驗(yàn)和較陡坡實(shí)驗(yàn)情況,為了研究緩坡情況下的沿岸流是否存在不同于陡坡情況的特征,本文通過物理模型實(shí)驗(yàn)和數(shù)值模擬研究了緩坡情況下的平均沿岸流和沿岸流不穩(wěn)定運(yùn)動(dòng),得到了緩坡地形條件下不同于陡坡情況下的波高、波浪增減水和平均沿岸流速度分布特征以及其對應(yīng)的沿岸流不穩(wěn)定運(yùn)動(dòng)特征。本文針對1：100和1：40平坡海岸進(jìn)行了不同波高和不同周期規(guī)則波和不規(guī)則波所產(chǎn)生的沿岸流的物理模型實(shí)驗(yàn),討論了所采用的被動(dòng)式水流循環(huán)系統(tǒng)所引起的沿岸流的沿岸均勻性,給出了緩坡情況下波高、波浪增減水和平均沿岸流速度分布特征：緩坡情況下,波浪破碎后,波高呈下凹趨勢,坡度越緩,波高下凹的趨勢越明顯；波浪增減水向岸增長趨勢逐漸變緩,坡度越緩,波浪增減水向岸增長趨勢越緩；1：100坡度平均沿岸流海岸一側(cè)分布呈下凹趨勢而相應(yīng)的1：40坡度呈上凸的趨勢。為了討論這一速度分布特征所產(chǎn)生的機(jī)理,本研究采用平均沿岸流數(shù)值模型進(jìn)行了平均沿岸流數(shù)值模擬,結(jié)果表明影響這些速度剖面特征的主要因素為破波帶內(nèi)波高分布和水底摩擦力表達(dá)式的選取,對后者更為敏感。1：100坡度海岸沿岸流速度剖面可由水流型水底摩擦力來計(jì)算出,而1：40坡度海岸沿岸流速度剖面可由波浪型水底摩擦力來計(jì)算出。為了顯示沿岸流不穩(wěn)定所引起的水流速度波動(dòng)特征,模型實(shí)驗(yàn)中采用了在流場中注入連續(xù)輸入的墨水來顯示速度的波動(dòng),并通過CCD記錄了顯示的結(jié)果。通過圖像處理,給出了對應(yīng)不同波況的墨水輸移特征以及它們所顯示的沿岸流不穩(wěn)定所引起的水流中渦運(yùn)動(dòng)的特征。沿岸流不穩(wěn)定的特征周期通過最大熵譜估計(jì)分析確定,特征波長可由墨水的波動(dòng)波長來顯示。采用沿岸流線性不穩(wěn)定分析給出了1：100和1：40坡度下不同的平均速度分布所導(dǎo)致的不同的不穩(wěn)定增長模式。1：100坡度多數(shù)波況沿岸流不穩(wěn)定存在前剪切和后剪切兩個(gè)不穩(wěn)定模式,而1：40坡度僅存在后剪切不穩(wěn)定模式。不穩(wěn)定分析所給出的不穩(wěn)定波動(dòng)周期和波長與實(shí)驗(yàn)結(jié)果進(jìn)行了對比。通過數(shù)值求解水平二維近岸環(huán)方程,研究了實(shí)驗(yàn)中1：100和1：40.海岸坡度各波況所對應(yīng)的沿岸流非線性不穩(wěn)定演化的特征,給出了緩坡情況下坡度、波高和不規(guī)則波對沿岸流不穩(wěn)定的影響以及不穩(wěn)定作用下的墨水?dāng)U散,特別討論了這些因素對由沿岸流不穩(wěn)定所引起的渦運(yùn)動(dòng)的影響。通過逐次近似的方法給出了波浪場(Stokes質(zhì)量輸移流和一階波浪水質(zhì)點(diǎn)速度二者疊加)中離散系數(shù)的解析表達(dá)式,并首次提出了二階離散系數(shù)。討論了Stokes質(zhì)量輸移流和一階波浪水質(zhì)點(diǎn)速度對波浪場中離散系數(shù)的貢獻(xiàn),討論了各部分離散系數(shù)的物理意義及量值大小。
[Abstract]:At present, the experimental research on coastal current is mainly aimed at the field experiment and the steep slope experiment. In order to study whether the coastal current under the gentle slope condition has the different characteristics from the steep slope situation, In this paper, through physical model experiment and numerical simulation, the mean coastal current and the unstable motion of coastal current in gentle slope are studied, and the wave height under gentle slope is obtained, which is different from that in steep slope. The characteristics of velocity distribution of wave increasing and decreasing water and average coastal current and their corresponding characteristics of unstable motion of coastal current are studied. In this paper, different wave heights, different periodic regular waves and irregular waves are carried out along the coast of flat slope at 1: 100 and 1:40. The physical Model experiment of Coastal current, The coastal uniformity of the coastal current caused by the passive flow circulatory system is discussed. The characteristics of wave height, wave increase and decrease and average coastal current velocity distribution in the case of gentle slope are given: in the case of gentle slope, when the wave is broken, the characteristics of the distribution of the wave height, the increase and decrease of the wave and the velocity of the average coastal current are given. The trend of wave height is concave, the lower the slope, the more obvious the concave trend of wave height, the slower the increasing trend of wave increasing and decreasing water, the slower the slope. The more slowly the trend of increasing and decreasing the water from wave to shore, the slower the trend of 1: 100 slope average along the coast is concave and the corresponding 1:40 slope is upward convex. In order to discuss the mechanism of this velocity distribution, In this study, the numerical model of average coastal current is used to simulate the average coastal current. The results show that the main factors affecting the characteristics of these velocity profiles are the distribution of wave height in the breaking zone and the selection of the expression of the bottom friction. More sensitive to the latter. 1: 100 slope, the coastal current velocity profile can be calculated from the flow type of bottom friction. At 1:40 slope, the coastal current velocity profile can be calculated by the wave bottom friction. In order to show the characteristics of the velocity fluctuation caused by the instability of the coastal current, In the model experiment, continuous inputted ink was injected into the flow field to show the fluctuation of velocity, and the result was recorded by CCD. The characteristics of ink transport corresponding to different wave conditions and the characteristics of vortex motion in the flow caused by the instability of the coastal current are given. The characteristic periods of the instability of the coastal current are determined by the maximum entropy spectrum estimation. The characteristic wavelengths can be shown by the wave wavelengths of ink. By using the linear instability analysis of coastal currents, different unstable growth modes. 1: 100 slopes with different average velocity distributions at 1: 100 and 1:40 slopes are given. There are two unstable modes of flow instability, pre-shear and post-shear. But at 1:40 slope, there is only a post-shear instability model. The unstable wave period and wavelength derived from the instability analysis are compared with the experimental results. The horizontal two-dimensional near-shore ring equation is solved numerically. In this paper, the characteristics of the nonlinear instability evolution of the coastal current corresponding to the wave conditions of the coastal slope are studied. The effects of slope, wave height and irregular waves on the instability of the coastal current and the ink diffusion under the unstable action are given. In particular, the influence of these factors on the vortex motion caused by the instability of the coastal current is discussed. The analytical expressions of the discrete coefficients in the wave field, Stokes mass transport and the first order wave water quality point velocity superposition are given by the successive approximation method. The contribution of the Stokes mass transport current and the point velocity of the first order wave water quality to the discrete coefficients in the wave field is discussed, and the physical meaning and the magnitude of the discrete coefficients of each part are discussed.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：P731.2
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本文編號：1676720