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Application of dual reciprocity boundary element method to predict acoustic attenuation characteristics of marine engine exhaust silencers 总被引:2,自引:0,他引:2
In marine engine exhaust silencing systems, the presence of exhaust gas flow influences the sound propagation inside the systems and the acoustic attenuation performance of silencers. In order to investigate the effects of three-dimensional gas flow and acoustic damping on the acoustic attenuation characteristics of marine engine exhaust silencers, a dual reciprocity boundary element method (DRBEM) was developed. The acoustic governing equation in three-dimensional potential flow was derived first, and then the DRBEM numerical procedure is given. Compared to the conventional boundary element method (CBEM), the DRBEM considers the second order terms of flow Mach number in the acoustic governing equation, so it is suitable for the cases with higher Mach number subsonic flow. For complex exhaust silencers, it is difficult to apply the single-domain boundary element method, so a substructure approach based on the dual reciprocity boundary element method is presented. The experiments for measuring transmission loss of silencers are conducted, and the experimental setup and measurements are explained. The transmission loss of a single expansion chamber silencer with extended inlet and outlet were predicted by DRBEM and compared with the measurements. The good agreements between predictions and measurements are observed, which demonstrated that the derived acoustic governing equation and the DRBEM numerical procedure in the present study are correct. 相似文献
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轴系纵振对双层圆柱壳体水下声辐射的影响研究 总被引:6,自引:1,他引:5
采用有限元/边界元方法(FEM/BEM)对推进轴系纵振引起的双层圆柱壳水下辐射噪声特性进行研究.使用ANSYS有限元软件建立了流固耦合的有限元模型,计算了流-固耦合状态下结构振动位移响应.利用边界元技术对结构水下辐射噪声特性进行研究,并对推力轴承的布置位置和结构进行了改变,从而改变了激振力的大小及传递途径,对轴系纵振引起的结构水下辐射噪声起到了一定的改善. 相似文献
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半空间内结构声辐射研究 总被引:1,自引:0,他引:1
采用解析方法,以脉动球为例研究了以自由表面或刚性表面为界的半空间内的声辐射问题.重点研究了自由表面或刚性表面对结构辐射声功率和辐射方向性的影响.数值结果表明:在低频和自由表面距离脉动球源较近时,自由表面的存在会大大地减小脉动球源的辐射声功率,自由表面对辐射声功率的影响可高达-40dB左右.但随着频率和自由表面离脉动球源距离的增大,自由表面对脉动球源辐射声功率的影响会急剧地减小.当频率较高或自由表面距离球源较远时,自由表面对脉动球源辐射声功率的影响是不大的;刚性表面对脉动球源辐射声功率的影响远远小于自由表面对脉动球源辐射声功率的影响,其最大的影响也仅为 3dB.文中还讨论了用边界元法求解三维复杂结构在半空间内的声辐射问题,并进行了计算验证. 相似文献
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研究舱段结构振动、声辐射特性随分舱形式改变的变化规律,对潜艇结构声学优化设计具有十分重要的意义。从结构声学设计的角度出发,在保持相邻两个舱段总长度不变的情况下,调整两个舱段的长度,采用结构有限元法、结构有限元耦合流体边界元方法,以辐射声功率、湿表面均方法向速度和辐射效率作为衡量结构噪声辐射能力的主要衡量指标,系统地研究整个结构振动和声辐射特性。在流体部分的计算中,采用网格重叠算法,以提高计算效率。通过调整分舱形式,在一定频段,改变了整个舱段结构振动声学传递函数的谱峰频率,降低了谱峰幅值,因此,可以通过改变分舱形式以改变舱段结构声学特性,使设备激振力的谱峰频率与结构振动声学传递函数的谱峰频率错开,实现对辐射噪声的控制。 相似文献
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在海浪作用下的防波堤或护岸工程等水工物理模型试验中,一般采用淡水模拟海水。由于模型中淡水密度小于工程中的海水密度,会导致模型中水工建筑物或块体受到的浮力、压力、波浪力等比用海水时小,并使模型中水工建筑物或块体的稳定性相似受到影响。从工程角度考虑,这种影响是偏于危险的。文中基于重力相似准则,推导了考虑原型和模型水密度差异的相似关系。海水压力及波浪力可采用新的相似关系,对于可以控制密度的水工建筑物或人工块体,通过减小密度的办法减小质量,保证其运动相似。对于原型块石,为满足运动相似,可直接减小其质量,体积也相应减小。利用本文修正方法,将使波浪模型试验数据更接近真实情况,研究成果更科学、合理。 相似文献
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舰船声呐罩以及舱室、车厢等常见的非规则声腔受湍流边界层脉动压力随机面激励产生的水(气)动力噪声,已经或将成为声呐自噪声和舱室噪声的主要成因。文中以一个非规则形状的三维声腔为例,考虑声腔结构振动与内外声场的耦合,采用虚拟膜技术和集成模态法以及功率谱密度概念,建立了声腔受湍流边界层脉动压力随机面激励的自噪声计算模型和方法。数值计算分析表明:虚拟膜技术和集成模态法可用于舰船声呐罩以及列车和汽车车厢等非规则声腔自噪声计算的声学建模,预报声腔内部水动力噪声或气动力噪声的低中频分量,具有数值方法能够模拟复杂形状声腔和解析方法相应的声振耦合方程维数少的优点。 相似文献
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基于改进傅立叶级数方法,将矩形板振型函数表示为包含正弦三角级数的改进傅立叶级数,从而有效地克服结构在边界处存在的不连续性,建立了一般边界条件下矩形薄板结构振动声辐射的分析方法,并对薄板结构的振动声辐射特性进行了研究。文中还建立了薄板结构的位移容许函数,然后基于最小势能原理求解了系统的Lagrange函数,最后利用Rayleigh-Ritz法对方程求解从而获得薄板自由振动的模态信息;在此基础上,基于Rayleigh积分公式推导出了薄板振动、辐射声压和声功率的表达式,研究了结构特性参数及边界条件对薄板振动声辐射的影响,通过有限元软件和参考文献的比对分析,验证了改进方法的正确性和有效性。 相似文献
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为避免尺度效应对噪声性能的影响,文章研究探索了在实尺度条件下装船后喷水推进器噪声声源的数值计算方法。首先,基于分离涡模型对国外某喷水推进泵内部非定常流场进行了数值模拟,将计算得到的不同转速下泵的功率值与厂商提供数据进行对比,最大误差在2.0%以内,验证了数值计算方法的准确性和有效性。其次,完成了实尺度条件下某"船体+喷水推进泵+进水流道"系统带自由液面的非定常流场的数值计算。提取了实船条件下喷水推进器流道进口处的不均匀速度场,将其加载到单个喷水推进器数值计算模型的进口边界。进而,采用分离涡模型对该船后"喷水推进泵+进水流道"内部非定常流场脉动压力进行数值计算,分析了各个特征截面压力脉动的频域特性,为下一步准确计算喷水推进器噪声提供了有效的脉动流场信息。 相似文献
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[Objective]This paper proposes a method for calculating the acoustic and vibration response of underwater cylindrical shell structures based on land-based vibration test results.[Methods]An axisymmetric boundary element method (BEM) is introduced to describe the radiation acoustic field of the shell. The relationship of acoustic pressure at the nodal point of the generatrix with velocity is obtained by solving the numerical solution of the boundary element integral equation, then the acoustic radiation impedance matrix of the outer surface of the shell and acoustic transfer vector (ATV) are constructed. Based on the assumption that the low-order vibration mode of an underwater cylindrical shell is the same as that of an onshore cylindrical shell, combined with the modes and acoustic radiation impedance matrix of an onshore cylindrical shell, the modal added mass and damping are calculated. [Results]The natural frequency calculation formula of the underwater cylindrical shell is established on the basis of the onshore mode, and the calculation method of underwater vibration response and acoustic radiation characteristics with the vibration response in air as input is obtained based on mode superposition method.[Conclusion ] The numerical results of a typical cylindrical shell with internal structure show that the method meets the engineering accuracy requirements. © 2023 Chinese Journal of Ship Research. All rights reserved. 相似文献
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WANGSan-de YANGDe-sen SHISheng-guo FANGEr-zheng 《船舶与海洋工程学报》2005,4(1):54-59
In this paper, the vibration and sound radiation of the underwater complex shell-structure which is the cylindrical shell with hemi-spherical shell on the ends are studied by statistical energy analysis (SEA). The whole shell-structure is divided into the four subsystems, and the SEA physical model and power flow balance equations among these subsystems are established. The similitude relations of input power, coupling loss factor and modal density of the subsystems between the complex shell-structure and its scaled-down model are analyzed. According to the similitude theory and power flow balance equations, when the immerged shell-structures are excited, the similar relations of spatially averaged vibration response and underwater radiating sound power are established for the complex shell-structure and its scaled-down model. 相似文献
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A general and efficient scaled method for stiffened plates subjected to combined longitudinal compression and lateral pressure is proposed based on slenderness, simply by adjusting the number of stiffeners. The design method makes it easier to determine the dimensions of the scaled model for a given scale ratio compared with the previously proposed method. The emphasis is on the influence of the plate slenderness, the column slenderness, and the non-dimensional parameter of the lateral pressure on the ultimate strength. By maintaining the consistency of the plate slenderness and column slenderness, the proposed method is applicable for designing scaled models with materials of different yield stresses and Young's moduli. A similar effect of the lateral pressure on the ultimate strength of the prototype and scaled models is achieved by maintaining the non-dimensional parameter. In addition, the applicability of the scaled method to the initial deflection is considered, which provides a reference for similar models. The similitude of the scaled method is verified for several typical buckling modes, including the beam–column, tripping, web and overall collapse modes. Given the numerical results, the proposed general and fast scaled method can provide reasonable dimensions of scaled stiffened plates subjected to combined loads. 相似文献
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本文提出一种新的船模自航模型化方法以“消除”船-桨干扰总理2的惊工影响,首先讨论船-桨组合体绕流(平均流动)应满足的相似准则,其中引进了两个新的准则以联系船 尾流的特征;尾流宽度与速度亏损,讨论了满足这些准则的模拟条件和方法,给出满足相似条件的船模-实船性能关系式,最后讨论了新模拟方法在船旋螺旋桨空的与噪声模型试验中的应用。 相似文献