發(fā)布時間：2018-07-28 14:40

【摘要】：近年來,由于沿海地區(qū)的經(jīng)濟(jì)發(fā)展,沿岸建設(shè)和沿岸環(huán)境保護(hù)問題逐漸受到人們的重視,沿岸流問題也隨之成為熱點(diǎn)研究對象。本文以已有的平直斜坡上的沿岸流實(shí)驗(yàn)為基礎(chǔ),研究了沿岸流不穩(wěn)定運(yùn)動的傳播特性和垂直岸線方向的能量變化特性,為今后更深入的研究沿岸流不穩(wěn)定運(yùn)動以及近岸低頻運(yùn)動建立一定的基礎(chǔ),因?yàn)?這對于更加深入探究近岸復(fù)雜水動力學(xué)特性具有比較重要的意義。本文研究結(jié)果對于近岸污染物、沉積物和泥沙的輸移也有一定的參考價值。本文圍繞上述內(nèi)容主要作了以下幾方面工作:1.首先基于相關(guān)性分析原理,分析沿岸流不穩(wěn)定運(yùn)動的傳播特性。對所有實(shí)驗(yàn)波況(地形分為1:100坡和1:40坡;入射波分為規(guī)則波和不規(guī)則波)采集到的流速時間歷程進(jìn)行相關(guān)性分析,具體而言,對兩不同列的流速儀的流速時間歷程進(jìn)行兩兩相關(guān)性分析,得到最大相關(guān)系數(shù)和對應(yīng)的延遲時間,再通過確定相關(guān)系數(shù)相對最大,延遲時間相對較小的兩流速儀,由三角形法則得出沿岸流不穩(wěn)定運(yùn)動的偏向角,即沿岸流不穩(wěn)定運(yùn)動的傳播方向,并分析不同地形、波況下產(chǎn)生偏移的原因。結(jié)果表明在入射波為不規(guī)則波情況下,沿岸流不穩(wěn)定運(yùn)動向離岸方向的偏向角在15°到30°左右,且隨入射波波高、周期的增大而增大,同時坡度也對結(jié)果有一定影響,陡坡時的偏向角明顯大于緩坡;沿岸流不穩(wěn)定運(yùn)動在入射波為規(guī)則波情況下,沿岸流不穩(wěn)定運(yùn)動向離岸方向的偏向角在15°左右,入射波的波高和周期對偏向角大小有一定影響,但對于坡度的影響,緩坡時的偏向角明顯大于陡坡。之所以沿岸流不穩(wěn)定運(yùn)動的方向有一定偏移而非平行于沿岸,在實(shí)際情況下,由于垂向環(huán)流系統(tǒng)的影響,造成向海方向偏移,并且床底部受海底回流的作用更加強(qiáng)烈,而質(zhì)量輸移流則對其表面附近的作用稍強(qiáng)。2.利用最大熵譜分析沿岸流不穩(wěn)定運(yùn)動在垂直岸方向的能量的變化特性,還分析了入射波波況對其能量的變化的影響。對所有實(shí)驗(yàn)波況采集到的流速時間歷程,進(jìn)行最大熵譜分析。對某一個波況而言,得到垂直岸線方向每一個流速儀位置處流速時間歷程的最大熵譜,進(jìn)而確定出三個最佳頻率,并利用三角函數(shù)回歸法求出這三個頻率對應(yīng)的幅值。這三個頻率中,其中一個為沿岸流不穩(wěn)定運(yùn)動,根據(jù)波能與振幅的關(guān)系,通過幅值的變化來分析沿岸流不穩(wěn)定運(yùn)動的能量變化。另外,本文還研究了另外兩個最佳頻率的特性,并對它們是否為邊緣波的猜想進(jìn)行了判定。結(jié)果表明,在距離岸線位置很近時,由于水深較淺,還沒有沿岸流不穩(wěn)定運(yùn)動的存在,所以此時另外兩個低頻運(yùn)動的能量會大于沿岸流不穩(wěn)定運(yùn)動;隨著沿岸距離的增加,此時沿岸流不穩(wěn)定運(yùn)動存在,另外兩個低頻運(yùn)動與沿岸流不穩(wěn)定運(yùn)動的能量比值呈增大趨勢,在平均沿岸流達(dá)到最大時達(dá)到峰值,之后呈減小趨勢。這種變化趨勢與沿岸流不穩(wěn)定運(yùn)動的變化趨勢相同。另外,入射波波高和周期的變化對這兩個低頻波運(yùn)動的能量有一定影響,但沒有明顯的隨之增大或減小的趨勢;對其他低頻成分進(jìn)行邊緣波判定,結(jié)果表明在三個最佳頻率中只有規(guī)則波情況下的0.03(0.04)Hz的低頻運(yùn)動為邊緣波波動。3.利用小波互譜研究了沿岸流不穩(wěn)定運(yùn)動傳播的時間-頻率特性。利用小波互譜分析了所有波況下沿岸流不穩(wěn)定運(yùn)動傳播的時間-頻率特性,文中將所有實(shí)驗(yàn)波況分為規(guī)則波和不規(guī)則波入射兩類進(jìn)行分析。基于所獲得的小波互相關(guān)等值線圖,分析入射波高、周期、地形對其傳播時-頻特性的影響。結(jié)果表明,三個主要頻率的相關(guān)程度都按自身的波動周期沿時滯橫軸周期性變化,且相關(guān)程度都較高,其中沿岸流不穩(wěn)定運(yùn)動的相關(guān)系數(shù)絕對值峰值達(dá)0.8的相關(guān)度,在整個時域都有周期變化的時滯和固定的相位差,波動穩(wěn)定,說明在破波點(diǎn)附近存在著強(qiáng)度較大并且穩(wěn)定波動的沿岸流不穩(wěn)定運(yùn)動。坡度對相關(guān)程度具有一定的影響,陡坡情況下的互相關(guān)等值線圖具有更加明顯的周期性和更加集中的峰值,而入射波高、周期對相關(guān)程度的影響不大,從整體上來說,由于規(guī)則波和不規(guī)則波的破波帶寬度不同,導(dǎo)致了不規(guī)則波的相關(guān)程度的峰值絕對值要大于規(guī)則波。
[Abstract]:In recent years, due to the economic development of coastal areas, the coastal construction and coastal environmental protection have gradually been paid attention to, and the problem of coastal flow has become a hot topic. Based on the existing coastal flow experiments on the straight slope, the energy of the propagation and vertical shore direction of the unsteady motion of the coastal flow is studied. The change characteristics will establish a certain foundation for the further study of coastal flow instability movement and near shore low frequency movement, because it is of great significance for further exploring the complex hydrodynamic characteristics of the near shore. The results of this study also have some reference value for the transportation of near shore pollutants, sediment and sediment. The main work of this paper is as follows: 1. first, based on the principle of correlation analysis, the propagation characteristics of the unsteady motion of the coastal flow are analyzed, and the correlation analysis is made for all experimental wave conditions (the terrain is divided into 1:100 slope and 1:40 slope, the incident wave is divided into regular and irregular waves). The 22 correlation analysis is carried out on the velocity time history of the two different column flow meters. The maximum correlation coefficient and the corresponding delay time are obtained. By determining the relative maximum coefficient of the correlation coefficient and the less delay time, the deviation angle of the unstable movement of the coastal flow is obtained by the triangle rule, that is, the propagation of the unsteady motion of the coastal current. The results show that the deviation angle of the unstable movement of the coastal current to the offshore direction is about 15 to 30 degrees, and increases with the increase of the incident wave, and the slope also has a certain influence on the result, and the steep slope deviates to Jiao Mingxian. In the case of regular waves, the instability movement of the coastal flow is about 15 degrees to the deviation angle of the offshore direction. The wave height and the period of the incident wave have a certain influence on the deflection angle, but the slope angle is obviously larger than the steep slope. The direction has a certain deviation, not parallel to the coast, in fact, due to the influence of the vertical circulation system, it causes the direction of the sea direction, and the bottom of the bed is more strongly affected by the undersea backflow, while the mass transfer flow is slightly stronger by.2. using the maximum entropy spectrum to analyze the unsteady movement of the coastal flow in the vertical direction. The effect of the energy change is also analyzed. The maximum entropy spectrum analysis is carried out for the velocity time history collected by all experimental wave states. For a certain wave state, the maximum entropy spectrum of the velocity time calendar is obtained at the position of each velocity meter in the direction of the vertical shore line, and then three optimal frequencies are determined. Rate, and using the trigonometric function regression method to find the corresponding amplitude of the three frequencies. In these three frequencies, one of them is the unstable motion of the coastal flow. According to the relation between the wave energy and the amplitude, the variation of the amplitude is used to analyze the energy change of the unstable motion of the coastal flow. In addition, the characteristics of the other two other optimal frequencies are also studied and the results are also studied. The results show that the boundary wave's conjecture has been determined. The results show that there is no unstable movement of the coastal flow because of the shallow depth of the shore line, so the energy of the other two other low-frequency motions will be larger than the unstable movement of the coastal flow, and along with the increase of the coastal distance, the unsteady movement of the coastal flow exists, and the other is the existence of the unsteady movement of the coastal flow. The energy ratio of the two low frequency and coastal unsteady movement increases, and reaches the peak when the average coastal flow reaches the maximum and then decreases. This trend is the same as the trend of the unstable movement of the coastal flow. In addition, the variation of the incident wave height and the period of the wave is certain for the energy of the two low frequency waves. There is no obvious tendency to increase or decrease with it, and the edge wave of other low-frequency components is determined. The results show that the low frequency motion of 0.03 (0.04) Hz under the condition of the regular wave at the three best frequency is the edge wave motion.3. using the wavelet cross spectrum to study the time and frequency characteristics of the unsteady motion of the coastal current. The wave cross spectrum is used to analyze the time and frequency characteristics of the unsteady motion of the coastal flow under all wave conditions. All the experimental waves are divided into two categories: regular waves and irregular waves. Based on the obtained wavelet cross-correlation contour map, the influence of incident wave height, period and terrain on the time frequency characteristics of the wave is analyzed. The results show that three The correlation degree of the main frequency varies periodically along the time lag axis, and the correlation degree is high. The correlation coefficient of the correlation coefficient of the unsteady motion of the coastal flow is up to 0.8, and the time delay and the fixed phase difference are stable in the whole time domain, which indicates the existence of the fluctuation near the broken wave point. The slope has a certain influence on the correlation degree, and the cross correlation contour map in the case of steep slope has more obvious periodicity and more concentrated peak, but the influence of the period on the correlation degree is not great, from the rule wave and the irregularity from the whole. The width of wave breaking band is different, leading to the absolute absolute value of the degree of correlation of irregular waves is greater than regular waves.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TV139.2

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