舰船柔性舵流噪声产生机理研究
发布时间：2018-12-25 10:32
【摘要】：流噪声是舰船噪声的主要来源之一，，随着机械噪声和螺旋桨噪声得到有效控制，流噪声问题日益突出。本文以二维舵体绕流问题为研究对象，研究了刚性舵、柔性舵绕流的非定常流动现象，对流噪声的产生机理进行了分析。考虑了流体-舵体之间的相互作用，分析了舵体的柔性变形对流动中声源的影响。研究了舵体绕流噪声在空间的传播特性、噪声的频谱特性，并进一步分析了舵体变形对远场噪声的影响。 首先，利用大涡模拟方法对NACA0018翼型的非定常绕流场进行了仿真。在不同的攻角下，大涡模拟方法较准确地捕捉到了壁面附近的流场结构，结果与文献吻合较好；基于获得的非定常流场信息，利用FW-H方程对远场的监测点处的噪声进行了计算，在监测点的噪声频谱特性中捕捉到了试验中的特征频率。通过结果与已有试验结果的对比，验证了本文所采用的绕流噪声算法的可靠性。 其次，利用大涡模拟方法对不同攻角和来流速度下的刚性舵非定常绕流场进行了仿真。壁面压力脉动的主要频率集中在2000Hz以下的频段，随着攻角的增大，主要脉动压力的频率减小，脉动幅值逐渐增大；压力脉动的主要频率和脉动幅值均随着流速的增大而增大。 接着，建立了舵体-流体耦合模型，基于弱耦合流固耦合算法和大涡模拟方法对不同工况下的柔性舵非定常绕流场进行了仿真。柔性舵在两侧压差的作用下发生偏转，受涡脱落的影响，舵体尾缘不停地作小幅振荡；0°攻角是一个特殊的工况，涡脱落是一个严格的周期性过程，此时涡脱落频率与壁面的压力脉动频率一致；舵体的柔性变形有效地控制了流动分离，减小了湍流区域和尾流的紊乱，柔性舵对湍流流动的抑制作用攻角越大越明显，使得压力脉动的幅值大大降低。 最后，基于刚性舵、柔性舵的非定常流场仿真结果，利用考虑具有任意运动固体边界的流动噪声问题的FW-H方程对刚性舵绕流和柔性舵绕流的远场噪声辐射进行了计算，获得了刚性舵、柔性舵绕流的壁面偶极子源分布、远场噪声辐射特性，并进行了对比分析。转捩区的壁面偶极子源最强，其次是湍流区，层流区的壁面偶极子源最弱，相对刚性舵，舵体的柔性变形显著减弱了壁面偶极子强度；舵体绕流噪声在空间上的传播表现为偶极子的特征，总声压级在弦线方向上最小；壁面偶极子源强度、辐射噪声水平均随着攻角的增大、来流速度的提高而增大；远场噪声的频谱特性与壁面的压力脉动频谱特性相似。
[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 掳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.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U661.44
本文编号：2391061
[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 掳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.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U661.44
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