本文選題：小波變換 + 沿岸流　； 參考：《太原理工大學(xué)》2015年碩士論文

【摘要】：近海岸區(qū)域及海岸帶是受環(huán)境影響較為嚴(yán)重的地區(qū)，這是因?yàn)椴ɡ说难莼捌扑闀?huì)導(dǎo)致沿岸流不穩(wěn)定運(yùn)動(dòng)規(guī)律十分的復(fù)雜，會(huì)影響到沿岸上污染物復(fù)雜的擴(kuò)散規(guī)律。自從人們發(fā)現(xiàn)沿岸流不穩(wěn)定運(yùn)動(dòng)以來(lái)，許多國(guó)內(nèi)外學(xué)者對(duì)沿岸流不穩(wěn)定運(yùn)動(dòng)及其現(xiàn)象進(jìn)行了廣泛的研究，發(fā)現(xiàn)沿岸流不穩(wěn)定運(yùn)動(dòng)對(duì)近海岸區(qū)域污染物及沉積物輸移的研究有著重要的意義，深入了解沿岸流不穩(wěn)定運(yùn)動(dòng)的理論可以使我們更好的處理近海岸區(qū)域的復(fù)雜問(wèn)題。 為了更加直接、清晰、全面的認(rèn)識(shí)沿岸流不穩(wěn)定運(yùn)動(dòng)的特性，本文主要利用小波分析方法和考慮底摩擦的沿岸流不穩(wěn)定模型來(lái)研究其時(shí)空變化特性和沿岸流不穩(wěn)定模式變化。 首先，采用小波方法對(duì)不規(guī)則波致沿岸流不穩(wěn)定運(yùn)動(dòng)時(shí)空變化進(jìn)行研究。利用小波方法得到流速時(shí)間歷程的小波譜，通過(guò)對(duì)小波譜的分析研究沿岸流不穩(wěn)定運(yùn)動(dòng)的時(shí)空變化，詳細(xì)分析了平直斜坡上、兩種坡度下沿岸及垂直岸方向的沿岸流不穩(wěn)定運(yùn)動(dòng)時(shí)空變化特征及其和邊緣波的相互聯(lián)系和影響。 其次，通過(guò)建立考慮底摩擦的不穩(wěn)定模型，根據(jù)所給出的沿岸流單峰速度剖面（n3和n6）和地形數(shù)值計(jì)算出在平直斜坡上、坡度為1:100條件下，不同底摩擦系數(shù)對(duì)應(yīng)的沿岸流不穩(wěn)定運(yùn)動(dòng)的增長(zhǎng)率、傳播速度隨波數(shù)的變化情況和擾動(dòng)速度隨岸線距離的分布。 最后，在給定了沙壩地形坡度為1:40和1:100條件下，模擬出了雙峰速度剖面，利用沿岸流線性不穩(wěn)定模型計(jì)算得出這兩種坡度情況下沿岸流不穩(wěn)定增長(zhǎng)率、傳播速度隨波數(shù)的變化情況和沿岸流擾動(dòng)速度隨岸線距離的分布。 通過(guò)小波分析對(duì)沿岸流不穩(wěn)定運(yùn)動(dòng)時(shí)空變化特性進(jìn)行研究，發(fā)現(xiàn)沿岸流不穩(wěn)定運(yùn)動(dòng)產(chǎn)生后會(huì)出現(xiàn)連續(xù)性現(xiàn)象，并且不會(huì)與低頻波以及其他形式的低頻波有能量上的交換；沿岸流不穩(wěn)定運(yùn)動(dòng)產(chǎn)生的波動(dòng)在沿岸方向相比垂直岸方向的波動(dòng)能量顯得更強(qiáng)烈；沿岸流不穩(wěn)定運(yùn)動(dòng)隨岸線距離的增加會(huì)提前產(chǎn)生能量；坡度的增大會(huì)使沿岸流不穩(wěn)定運(yùn)動(dòng)在沿岸和垂直岸方向上的作用變得更強(qiáng)；邊緣波可以和沿岸流不穩(wěn)定運(yùn)動(dòng)同時(shí)在垂直岸線方向和沿岸方向存在；相同條件下沿岸流不穩(wěn)定運(yùn)動(dòng)具有一定的可重現(xiàn)性。在平直斜坡上、兩種速度剖面并考慮底摩擦的沿岸流不穩(wěn)定增長(zhǎng)率的研究結(jié)果表明，底摩擦?xí)绊懷匕读鞑环�(wěn)定運(yùn)動(dòng)，，底摩擦系數(shù)越大沿岸流不穩(wěn)定增長(zhǎng)率越��；在兩種速度剖面下，不同底摩擦系數(shù)下的增長(zhǎng)率極值對(duì)應(yīng)的波數(shù)是固定不變的；對(duì)沿岸流不穩(wěn)定模型數(shù)值計(jì)算出的擾動(dòng)速度進(jìn)行了分析，發(fā)現(xiàn)有無(wú)底摩擦情況下兩種速度剖面所對(duì)應(yīng)的沿岸流擾動(dòng)速度都呈現(xiàn)出周期性波動(dòng)。通過(guò)對(duì)文中六種雙峰速度剖面、沙壩地形坡度1:40和1:100條件下沿岸流不穩(wěn)定運(yùn)動(dòng)增長(zhǎng)率變化情況的研究，表明有無(wú)底摩擦情況下的沿岸流不穩(wěn)定運(yùn)動(dòng)幾乎都會(huì)出現(xiàn)兩種增長(zhǎng)模式，兩種模式都是由沿岸流的前剪切及后剪切所引起的；通過(guò)沿岸流不穩(wěn)定模型計(jì)算出的擾動(dòng)速度場(chǎng)發(fā)現(xiàn)，兩種坡度下的擾動(dòng)速度場(chǎng)都呈現(xiàn)出周期性波動(dòng)；坡度影響沿岸流不穩(wěn)定運(yùn)動(dòng)增長(zhǎng)率和破波點(diǎn)發(fā)生的位置，坡度增大會(huì)使沿岸流不穩(wěn)定運(yùn)動(dòng)增長(zhǎng)率變大，而且沿岸流不穩(wěn)定運(yùn)動(dòng)破波點(diǎn)發(fā)生的位置越靠近海岸。
[Abstract]:The coastal zone and coastal zone are more seriously affected by the environment. This is because the evolution and fragmentation of the waves will lead to the complexity of the irregular motion of the coastal flow, which will affect the complex diffusion of pollutants along the coast. Since the unstable movement of the coastal flow has been found, many domestic and foreign scholars have been unstable to the coastal flow. The constant motion and its phenomenon have been widely studied. It is found that the unsteady motion of the coastal flow is of great significance to the study of the transport of pollutants and sediments near the coastal region. The theory of the unsteady movement of the coastal currents can make us better deal with the complex problems of the coastal areas.
In order to make a more direct, clear and comprehensive understanding of the characteristics of the coastal flow instability, this paper mainly uses the wavelet analysis method and the unsteady model of the coastal flow considering the bottom friction to study the temporal and spatial variation characteristics and the variation of the coastal flow instability model.
Firstly, the wavelet method is used to study the spatio-temporal variation of the unsteady wave induced unsteady motion of the coastal currents. The wavelet method is used to obtain the small wave spectrum of the time history of the flow. By the analysis of the small wave spectrum, the temporal and spatial variation of the unsteady motion of the coastal current is studied, and the coastal and vertical bank directions on the flat slope and the two slopes are analyzed in detail. The temporal and spatial variation characteristics of flow instability and its relationship with edge waves.
Secondly, by setting up an unstable model considering the bottom friction, the growth rate of the unsteady motion of the coastal flow is calculated on the flat slope based on the single peak velocity profile (N3 and N6) and the terrain value given on the flat slope. The gradient of the slope is 1:100, and the propagation velocity varies with the wave number and the velocity of the disturbance along the shore. The distribution of the line distance.
At last, the Shuangfeng velocity profile is simulated under the condition of the slope of the sand dam at 1:40 and 1:100, and the unsteady growth rate of the coastal flow is calculated with the coastal streamline instability model. The variation of the propagation velocity with the wave number and the distribution of the coastal flow disturbance velocity along with the distance of the shore line.
The time and space characteristics of the unsteady motion of the coastal flow are studied by the wavelet analysis. It is found that the instability of the coastal flow will occur continuously after the unsteady movement of the coastal flow, and does not have the energy exchange with the low frequency waves and other forms of low frequency waves; the waves produced by the unsteady motion of the coastal flow are in the direction of the vertical bank in the direction of the coastal flow. The dynamic energy appears more intense; the unsteady motion of the coastal flow will generate energy in advance with the increase of the coastline distance; the increase of the slope will make the unsteady movement of the coastal flow stronger in the direction of the coastal and vertical banks, and the edge wave can exist in the vertical and coastal directions at the same time as the unsteady movement of the coastal flow; The unsteady motion of the coastal flow has a certain reproducibility. On the flat slope, the results of two velocity profiles and the unsteady growth rate of the coastal current considering the bottom friction show that the bottom friction will affect the unsteady movement of the coastal flow, the smaller the bottom friction coefficient is, the smaller the growth rate of the coastal flow instability is, and the difference is different under the two velocity profiles. The wave number corresponding to the extreme value of the growth rate under the bottom friction coefficient is fixed and constant, and the perturbation velocity calculated by the numerical calculation of the coastal flow instability model is analyzed. It is found that the coastal flow disturbance velocity corresponding to the two velocity profiles under the case of bottomless friction shows a periodic fluctuation. Six kinds of Shuangfeng velocity profiles in the paper, sand, sand, are found. The study on the variation of the growth rate of the unsteady movement of the coastal flow under the condition of the dam terrain at 1:40 and 1:100 shows that there are almost two growth modes in the unsteady movement of the coastal flow under the condition of bottom friction. The two models are all caused by the front and rear shear of the coastal flow, and the disturbance calculated by the coastal flow instability model. The dynamic velocity field shows that the disturbance velocity field under the two slopes has periodic fluctuation, and the slope affects the growth rate of unsteady movement and the location of the breaking point. The increase of the slope will increase the growth rate of the unstable movement of the coastal flow, and the location of the breaking point of the unstable coastal flow is closer to the coast.

【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：P731.2

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本文編號(hào)：1895887