發(fā)布時(shí)間：2018-01-11 06:23

  本文關(guān)鍵詞：內(nèi)波對(duì)水下聲信號(hào)時(shí)間相關(guān)性影響的數(shù)值和實(shí)驗(yàn)研究　出處：《中國(guó)海洋大學(xué)》2015年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 線性內(nèi)波 時(shí)間相關(guān)半徑 匹配場(chǎng) 絕熱近似 耦合簡(jiǎn)正波

【摘要】：海洋中內(nèi)波的存在會(huì)使聲信號(hào)的時(shí)間相關(guān)半徑變小。受物理介質(zhì)影響的信號(hào)時(shí)間相關(guān)半徑表明了信號(hào)由完全相關(guān)變?yōu)椴幌嚓P(guān)時(shí)經(jīng)過的時(shí)間尺度,它是聲納目標(biāo)的檢測(cè)與識(shí)別、匹配場(chǎng)聲源定位以及水下通訊的重要技術(shù)指標(biāo)。本文通過數(shù)值仿真和海上實(shí)驗(yàn)數(shù)據(jù)處理,分析了內(nèi)波對(duì)聲場(chǎng)時(shí)間相關(guān)性的影響,得到了典型聲傳播條件下信號(hào)的匹配場(chǎng)時(shí)間相關(guān)半徑以及時(shí)間相關(guān)半徑在距離-深度空間上的分布�；�于拋物方程(PE)理論,Monte-Carlo數(shù)值仿真了線性內(nèi)波存在時(shí)聲場(chǎng)的時(shí)間相關(guān)函數(shù),得到時(shí)間相關(guān)性的空間分布。在前人PE仿真所采用的凍結(jié)聲學(xué)環(huán)境模型的基礎(chǔ)上提出了一種非凍結(jié)的環(huán)境模擬方法,時(shí)間相關(guān)性的數(shù)值結(jié)果表明,在一定的頻率和接收距離范圍內(nèi),凍結(jié)模型依然可靠,但頻率越高,接收距離越遠(yuǎn),可靠性越低。對(duì)距離-深度空間各個(gè)位置處聲場(chǎng)時(shí)間相關(guān)性的理論和數(shù)值研究發(fā)現(xiàn),時(shí)間相關(guān)性在空間上的分布具有與聲場(chǎng)干涉條紋類似的結(jié)構(gòu),聲場(chǎng)會(huì)聚區(qū)的時(shí)間相關(guān)性優(yōu)于影區(qū),隨機(jī)噪聲的存在使這個(gè)結(jié)論更加明顯。此外,聲源頻率f、接收距離R和聲速擾動(dòng)的統(tǒng)計(jì)標(biāo)準(zhǔn)差|δc|等參數(shù)的改變引起聲場(chǎng)干涉結(jié)構(gòu)的變化,導(dǎo)致時(shí)間相關(guān)半徑對(duì)其不再是對(duì)數(shù)坐標(biāo)下的線性依賴。在Monte-Carlo研究的同時(shí),提出了基于絕熱近似和耦合簡(jiǎn)正波理論的統(tǒng)計(jì)方法。研究結(jié)果表明：深遠(yuǎn)海聲傳播條件下,絕熱近似得到的匹配場(chǎng)時(shí)間相關(guān)半徑隨R、f和|δc|的冪指數(shù)關(guān)系與Monte-Carlo仿真和單向耦合方法的結(jié)果近似相同,但它高估了信號(hào)的時(shí)間相關(guān)半徑,且不能正確描述時(shí)間相關(guān)半徑的空間分布；淺海近距離聲傳播條件下,絕熱近似的計(jì)算結(jié)果具有一定的可靠性。本文發(fā)展的二維統(tǒng)計(jì)模型得到的匹配場(chǎng)時(shí)間相關(guān)半徑大于前人的三維模型,在本文參數(shù)范圍內(nèi),數(shù)值計(jì)算中一般考慮前5號(hào)內(nèi)波模態(tài)和幾十號(hào)簡(jiǎn)正波就可以保證數(shù)值結(jié)果的可靠性,但要得到時(shí)間相關(guān)半徑的空間分布需要考慮更多的簡(jiǎn)正波。對(duì)ASIAEX2001實(shí)驗(yàn)的聲學(xué)數(shù)據(jù)處理后得到,當(dāng)聲傳播路徑上出現(xiàn)強(qiáng)孤立子內(nèi)波時(shí),聲場(chǎng)的時(shí)間相關(guān)半徑明顯降低,某些時(shí)刻300Hz信號(hào)的時(shí)間相關(guān)半徑低于20s,500Hz信號(hào)的時(shí)間相關(guān)半徑甚至降到l 0s內(nèi)；信號(hào)頻率越高,時(shí)間相關(guān)半徑越短：且聲場(chǎng)的時(shí)間相關(guān)半徑在深度上有明顯起伏。由兩個(gè)位置不同的聲源S1和S2發(fā)射的400Hz信號(hào)在接收位置R處的時(shí)間相關(guān)半徑不同,S2-R路徑的時(shí)間相關(guān)半徑比S1-R路徑長(zhǎng)。這可能是由于內(nèi)波在S2-R路徑上的相位傳播速度小于S1-R路徑,聲源深度和地形的不同也可能對(duì)上述結(jié)果有所影響。PE仿真采用的凍結(jié)聲學(xué)環(huán)境忽略了內(nèi)波在傳播過程中波形和強(qiáng)度的變化,導(dǎo)致計(jì)算得到的時(shí)間相關(guān)半徑比實(shí)驗(yàn)數(shù)據(jù)處理的結(jié)果要長(zhǎng)。因此,建立更加完善的非凍結(jié)環(huán)境模型需要在發(fā)射與接收間布放足夠多的溫度鏈以監(jiān)測(cè)內(nèi)波傳播過程中的演變。
[Abstract]:The existence of internal waves in the ocean will make the time correlation radius of acoustic signal smaller. The time correlation radius of the signal affected by physical medium indicates the time scale of signal from complete correlation to irrelevant. It is an important technical index of sonar target detection and recognition, matching field source location and underwater communication. In this paper, the influence of internal wave on the time dependence of sound field is analyzed by numerical simulation and offshore experimental data processing. The time correlation radius of the matching field and the distribution of the time correlation radius in the distance-depth space are obtained under the typical sound propagation condition. The theory of the parabolic equation (PE) is used to obtain the distribution of the time-dependent radius of the signal in the range-depth space. The time correlation function of sound field in the presence of linear internal wave is simulated numerically by Monte-Carlo. Based on the frozen acoustic environment model used in previous PE simulation, a non-frozen environmental simulation method is proposed, and the numerical results of time correlation show that. In a certain range of frequency and receiving distance, the freezing model is still reliable, but the higher the frequency, the longer the receiving distance. The lower the reliability is, the more the theoretical and numerical study on the temporal correlation of sound field at each position in the range-depth space shows that the spatial distribution of temporal correlation has a structure similar to that of the interference fringes of sound field. The temporal correlation of the acoustic field convergence region is better than that of the shadow area, and the existence of random noise makes this conclusion more obvious. In addition, the sound source frequency f. The change of receiving distance R and the statistical standard deviation 未 c of the acoustic velocity disturbance leads to the change of the sound field interference structure. Therefore, the time-dependent radius is no longer a linear dependency in logarithmic coordinates. A statistical method based on adiabatic approximation and coupled normal wave theory is proposed. The results show that the time-dependent radius of the matching field obtained by adiabatic approximation depends on R. The power exponent relation of f and 未 c is approximately the same as that of Monte-Carlo simulation and unidirectional coupling method, but it overestimates the time-dependent radius of the signal. And the spatial distribution of time-dependent radius can not be correctly described. The calculated results of adiabatic approximation are reliable under the condition of near distance acoustic propagation in shallow water. The time correlation radius of the matching field obtained by the two-dimensional statistical model developed in this paper is larger than that of the previous three dimensional model. In the parameter range of this paper, the reliability of the numerical results can be guaranteed by considering the first 5 internal wave mode and the dozens of normal waves in the numerical calculation. But in order to obtain the spatial distribution of time-dependent radius, we need to consider more normal waves. After processing the acoustic data of ASIAEX2001 experiment, we can get that, when the strong soliton internal waves appear on the sound propagation path. The time correlation radius of sound field decreases obviously, and the time correlation radius of 300 Hz signal at some times is lower than that of 20 s ~ 500 Hz signal, even within 10 s. The higher the signal frequency. The shorter the time-dependent radius:. The time correlation radii of sound field fluctuate obviously in depth. The time correlation radii of 400 Hz signals transmitted by two different sound sources S1 and S2 are different at the receiving position R. The time-dependent radius of the S2-R path is longer than that of the S1-R path, which may be due to the fact that the phase propagation velocity of the internal wave in the S2-R path is lower than that in the S1-R path. The difference of sound source depth and topography may also affect the above results. The frozen acoustic environment used in PE simulation ignores the variation of the waveform and intensity of the internal wave in the process of propagation. The calculated time correlation radius is longer than that of experimental data processing. To establish a more perfect non-freezing environment model, enough temperature chains should be placed between the transmitter and receiver to monitor the evolution of internal wave propagation.
【學(xué)位授予單位】：中國(guó)海洋大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：P733.2;TB56

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