【摘要】：流噪聲是艦船噪聲的主要來(lái)源之一，，隨著機(jī)械噪聲和螺旋槳噪聲得到有效控制，流噪聲問(wèn)題日益突出。本文以二維舵體繞流問(wèn)題為研究對(duì)象，研究了剛性舵、柔性舵繞流的非定常流動(dòng)現(xiàn)象，對(duì)流噪聲的產(chǎn)生機(jī)理進(jìn)行了分析�？紤]了流體-舵體之間的相互作用，分析了舵體的柔性變形對(duì)流動(dòng)中聲源的影響。研究了舵體繞流噪聲在空間的傳播特性、噪聲的頻譜特性，并進(jìn)一步分析了舵體變形對(duì)遠(yuǎn)場(chǎng)噪聲的影響。 首先，利用大渦模擬方法對(duì)NACA0018翼型的非定常繞流場(chǎng)進(jìn)行了仿真。在不同的攻角下，大渦模擬方法較準(zhǔn)確地捕捉到了壁面附近的流場(chǎng)結(jié)構(gòu)，結(jié)果與文獻(xiàn)吻合較好；基于獲得的非定常流場(chǎng)信息，利用FW-H方程對(duì)遠(yuǎn)場(chǎng)的監(jiān)測(cè)點(diǎn)處的噪聲進(jìn)行了計(jì)算，在監(jiān)測(cè)點(diǎn)的噪聲頻譜特性中捕捉到了試驗(yàn)中的特征頻率。通過(guò)結(jié)果與已有試驗(yàn)結(jié)果的對(duì)比，驗(yàn)證了本文所采用的繞流噪聲算法的可靠性。 其次，利用大渦模擬方法對(duì)不同攻角和來(lái)流速度下的剛性舵非定常繞流場(chǎng)進(jìn)行了仿真。壁面壓力脈動(dòng)的主要頻率集中在2000Hz以下的頻段，隨著攻角的增大，主要脈動(dòng)壓力的頻率減小，脈動(dòng)幅值逐漸增大；壓力脈動(dòng)的主要頻率和脈動(dòng)幅值均隨著流速的增大而增大。 接著，建立了舵體-流體耦合模型，基于弱耦合流固耦合算法和大渦模擬方法對(duì)不同工況下的柔性舵非定常繞流場(chǎng)進(jìn)行了仿真。柔性舵在兩側(cè)壓差的作用下發(fā)生偏轉(zhuǎn)，受渦脫落的影響，舵體尾緣不停地作小幅振蕩；0°攻角是一個(gè)特殊的工況，渦脫落是一個(gè)嚴(yán)格的周期性過(guò)程，此時(shí)渦脫落頻率與壁面的壓力脈動(dòng)頻率一致；舵體的柔性變形有效地控制了流動(dòng)分離，減小了湍流區(qū)域和尾流的紊亂，柔性舵對(duì)湍流流動(dòng)的抑制作用攻角越大越明顯，使得壓力脈動(dòng)的幅值大大降低。 最后，基于剛性舵、柔性舵的非定常流場(chǎng)仿真結(jié)果，利用考慮具有任意運(yùn)動(dòng)固體邊界的流動(dòng)噪聲問(wèn)題的FW-H方程對(duì)剛性舵繞流和柔性舵繞流的遠(yuǎn)場(chǎng)噪聲輻射進(jìn)行了計(jì)算，獲得了剛性舵、柔性舵繞流的壁面偶極子源分布、遠(yuǎn)場(chǎng)噪聲輻射特性，并進(jìn)行了對(duì)比分析。轉(zhuǎn)捩區(qū)的壁面偶極子源最強(qiáng)，其次是湍流區(qū)，層流區(qū)的壁面偶極子源最弱，相對(duì)剛性舵，舵體的柔性變形顯著減弱了壁面偶極子強(qiáng)度；舵體繞流噪聲在空間上的傳播表現(xiàn)為偶極子的特征，總聲壓級(jí)在弦線方向上最小；壁面偶極子源強(qiáng)度、輻射噪聲水平均隨著攻角的增大、來(lái)流速度的提高而增大；遠(yuǎn)場(chǎng)噪聲的頻譜特性與壁面的壓力脈動(dòng)頻譜特性相似。
[Abstract]:Flow noise is one of the main sources of ship noise. With the effective control of mechanical noise and propeller noise, the flow noise problem becomes more and more serious. In this paper, the unsteady flow around the rigid rudder and the flexible rudder and the mechanism of the convection noise are studied. The fluid-rudder interaction is considered and the influence of the flexible deformation of the rudder body on the sound source in the flow is analyzed. In this paper, the propagation characteristics of the rudder body flow noise in space and the spectrum characteristic of the noise are studied, and the influence of rudder deformation on the far-field noise is analyzed. Firstly, the unsteady flow field around NACA0018 airfoil is simulated by large eddy simulation method. At different angles of attack, the large eddy simulation method captures the structure of the flow field near the wall accurately, and the results are in good agreement with the literature. Based on the unsteady flow field information obtained, the noise at the far field monitoring point is calculated by using FW-H equation, and the characteristic frequency of the test is captured in the noise spectrum characteristics of the monitoring point. By comparing the results with the experimental results, the reliability of the proposed algorithm is verified. Secondly, the unsteady flow field around the rigid rudder with different attack angles and incoming velocity is simulated by using large eddy simulation method. The main frequency of wall pressure pulsation is concentrated in the frequency band below 2000Hz. With the increase of attack angle, the frequency of main pulsating pressure decreases and the amplitude of pulsation increases gradually, and the main frequency and amplitude of pressure pulsation increase with the increase of flow velocity. Then, the rudder body-fluid coupling model is established, and the unsteady flow field around the flexible rudder under different conditions is simulated based on the weakly coupled fluid-solid coupling algorithm and the large eddy simulation method. The flexible rudder deflects under the pressure difference on both sides, which is affected by vortex shedding, and the rudder tail edge oscillates continuously. 0 擄angle of attack is a special condition, vortex shedding is a strict periodic process, and the frequency of vortex shedding is consistent with the pressure pulsation frequency of the wall. The flexible deformation of the rudder effectively controls the separation of the flow and reduces the turbulence region and wake disturbance. The larger the angle of attack of the flexible rudder to the turbulent flow is, the lower the amplitude of the pressure pulsation is. Finally, based on the simulation results of the unsteady flow field of the rigid rudder and the flexible rudder, the far-field noise radiation around the rigid rudder and the flexible rudder is calculated by using the FW-H equation considering the flow noise problem with arbitrary moving solid boundaries. The distribution of wall dipole source and far-field noise radiation characteristics of rigid rudder and flexible rudder are obtained and compared. In the transition region, the wall dipole source is the strongest, followed by the turbulent zone, and the laminar flow region has the weakest wall dipole source, relative rigid rudder, the flexible deformation of the rudder body significantly weakens the wall dipole strength. The noise around the rudder body propagates in space as a dipole, the total sound pressure level is the smallest in the direction of the chord, the intensity of the wall dipole source and the level of the radiation noise increase with the increase of the attack angle and the velocity of the incoming flow. The spectrum characteristics of far field noise are similar to those of wall pressure pulsation.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：U661.44

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