非紧致结构气动噪声数值积分预测方法研究

发布时间：2018-02-04 21:03

  本文关键词： 非紧致边界 气动噪声 数值预测 散射效应 可压缩流动　出处：《西北工业大学》2015年博士论文　论文类型：学位论文

【摘要】：非紧致结构气动噪声问题广泛地存在于航空航天、工业生产及交通运输等多个领域。大型民航飞行器在起飞、降落或飞行阶段所产生的气动噪声问题尤其严重,因而气动噪声的数值预测受到普遍的关注。混合计算气动声学(HCAA)方法简单易行,具有计算复杂度低、计算效率高和成本费用低等优点,被广泛用于工程实际应用。该方法的基本思路是将流场和声场分开求解,结合CFD手段获得近场流动数值解,然后通过声传播方程计算远场噪声。其中,Lighthill声比拟理论思想简洁且适用性强,可以快速求解噪声传播。为了研究非紧致结构引起的散射效应,本文基于Lighthill声比拟假设发展了非紧致结构的气动噪声数值预测模型,主要研究工作和创新点包括如下几个方面:(1)基于涡声理论和压力分解方法建立了低马赫流动气动噪声的声压积分方程,噪声计算包括物面散射声压计算和远场任意观察点声压计算两部分。对低马赫数圆柱绕流气动噪声进行数值预测,声场分布特征与Curle方程一致。考察湍流脉动与噪声传播之间的关系,结果显示噪声随频率的变化与湍流脉动的变化趋势一致。数值研究表明该方法能够精确求解低马赫数流动气动噪声,并且直观的反映了旋涡与声波之间的关系。(2)提出了一种非紧致边界气动噪声辐射散射统一积分计算方法。该方法将流场脉动量分解为流场数值计算捕获的主要由流体运动引起的流动脉动分量和流场计算未捕获的主要由噪声传播引起的声学脉动分量两部分,基于Lighthill的声比拟理论和格林函数波动方法获得声学计算的统一积分方程。采用二阶精度格式进行可压缩流动计算,通过统一积分方程得到非紧致边界的散射声压,然后求解远场任意观察点的声压。对二维、三维圆柱开展气动噪声数值计算,计算结果与文献结果吻合。数值研究表明本文方法能够减少流场高精度计算所需的工作量,而且能够捕获非紧致边界的散射效应,同时能够模拟可压缩流动气动噪声的声场特征。(3)针对复杂结构、包含多个物体的物理模型及振荡结构的气动噪声问题,提出了非紧致可渗透边界气动噪声数值积分计算方法。选取包围所有物体的光滑边界为可渗透边界,气动噪声计算包含可渗透边界散射声压计算和远场任意观察点声压计算两部分。对圆柱、Rod-Airfoil模型、30P30N翼型开展气动噪声数值计算,可渗透边界积分计算方法获得的结果与物面积分计算方法及文献结果吻合。数值研究表明可渗透边界气动噪声积分计算方法可以精确模拟非紧致边界的散射效应,能够降低计算复杂度,并有助于改善气动噪声的数值计算效率。(4)为避免飞行器起飞、降落或者低空飞行阶段地面边界散射声源计算所需的工作量,结合镜像源方法提出了半空间内非紧致边界气动噪声数值积分计算方法。通过二阶精度的DES模型进行流动数值模拟,采用非紧致边界积分方法进行散射声场计算。首先,对半空间内圆柱、NACA0012翼型及30P30N翼型开展气动噪声数值计算,结果表明半空间内地面边界的散射效应引起声场复杂且剧烈的变化。其次,开展亚音速方腔流动噪声数值预测,计算结果与高精度计算气动声学方法吻合,声压级随频率呈现逐渐递减的变化趋势。数值研究表明本文方法能够模拟非紧致边界和半空间边界的散射效应,无需求解地面边界散射声源,显著提高了半空间气动噪声的数值计算效率。(5)结合自由空间声传播方程,建立了运动非紧致边界时域格林函数积分方程,借助该方程和Lighthill声比拟理论可以考虑任意边界情形的噪声分布。选取圆柱为研究对象,在圆柱附近放置静止和运动点声源,所获得的远场噪声分布与解析解吻合,时域噪声的特征变化符合声波传播规律。对低马赫数流动圆柱绕流噪声进行数值预测,时域计算方法获得的结果与频域方法的结果及实验数据吻合,远场噪声随时间呈现周期性变化,噪声分布特征与流场脉动一致。数值研究表明本文方法可以考虑噪声的瞬时特征分布,并且能够精确模拟非紧致边界的散射效应。
[Abstract]:The non compact structure of the aerodynamic noise problem exists widely in many fields of aerospace, industrial production and transportation. Large civil aircraft during takeoff, landing or flight phase generated by the aerodynamic noise problem is particularly serious, so the numerical aerodynamic noise prediction has attracted universal attention. A hybrid computational aeroacoustics (HCAA) the method is simple and has low computational complexity, high computational efficiency and low cost advantages, is widely used in engineering practice. The basic idea of this method is to solve the flow field and sound field separation, combined with the CFD method to obtain numerical solutions of near field and far field noise, through the sound propagation equation. The Lighthill acoustic analogy theory of simple and strong applicability, can quickly solve the noise propagation. In order to study the scattering effect caused by the non compact structure, the Lighthill acoustic analogy hypothesis is developed based on non compact The aerodynamic noise prediction model, the main research work and innovations are as follows: (1) the pressure integral equation of vortex sound theory and method to establish the low pressure decomposition of Maher flow aerodynamic noise based on noise calculation including surface scattering pressure calculation and far-field arbitrary observation point pressure calculation of two parts. Low Maher number flow around a cylinder dynamic noise numerical prediction of acoustic field distribution, consistent with the Curle equation. To study the relationship between turbulence and noise propagation, the results showed that the changing noise with frequency changes and turbulence is consistent with the trend. The numerical results show that the method can accurately solve the low Maher number flow aerodynamic noise, and intuitive the reflects the relationship between vortex and sound. (2) proposed a method to calculate the non compact boundary aerodynamic noise radiation scattering. This method will be unified integral flow pulsation decomposition Capture for numerical calculation of flow field is mainly caused by the motion of the fluid flow fluctuation and flow field calculation are not captured by the acoustic ripple component is mainly caused by the noise propagation in two parts, the unified Lighthill acoustic analogy theory and Green function method for calculating acoustic wave based on integral equation. Using two order accuracy scheme for compressible flow computation. Get the scattering pressure non compact boundary through unified integral equations, then solving the far field sound pressure of arbitrary observation point. The two-dimensional, three-dimensional cylindrical of aerodynamic noise numerical calculation, the calculation results with the literature results. The numerical results show that this method can reduce the computation required for high precision field workload, scattering and capture the non compact at the same time boundary, can simulate the flow characteristics of the aerodynamic noise field can be compressed. (3) aiming at the complex structure, comprising a plurality of physical objects The model and the oscillatory structure of the aerodynamic noise problem, put forward the calculation method of aerodynamic noise can be non compact numerical integral gas permeable boundary. Select all objects surrounded by smooth boundary for permeable boundary, the aerodynamic noise calculation includes a permeable boundary scattering pressure calculation and far-field arbitrary observation point pressure calculation of the cylindrical part two, Rod-Airfoil model 30P30N, carry out the airfoil aerodynamic noise numerical calculation method for seepage boundary integral results obtained with the surface integral calculation method and literature results. The numerical results show that the scattering effect of permeable boundary integral aerodynamic noise calculation method can accurately simulate the non compact boundary, can reduce the computational complexity, and computational efficiency help to improve the aerodynamic noise. (4) in order to avoid the aircraft take-off, landing or low altitude flight phase ground boundary scattering source to calculate the required workload, combined with The image source method puts forward the calculation method of the half space boundary non compact aerodynamic noise numerical integration. Numerical simulation of flow through the DES model with two order accuracy, using non compact boundary integral method for scattering field calculation. Firstly, the half space within the cylinder, the NACA0012 airfoil and 30P30N airfoil aerodynamic noise to carry out the numerical calculation results show that the scattering effect in the half space ground boundary changes caused by complex and intense field. Secondly, carry out numerical flow noise in subsonic cavity prediction results with high precision computational aeroacoustics method consistent with the frequency of sound pressure level showed a trend of gradually decreasing. The numerical results show that this method can simulate the scattering effect of non compact boundary and half space the border, there is no need to solve the surface boundary scattering source, significantly improve the computational efficiency of the numerical aerodynamic noise of half space gas. (5) combined with the free space of sound The propagation equation is established, the movement of non compact time-domain Green function boundary integral equation, the equation and Lighthill acoustic analogy can be considered noise distribution of arbitrary boundary conditions. The cylinder as the research object, placing the stationary and moving point source in cylindrical near the far field noise distribution agreement with analytical solution, change characteristics of time domain the noise with sonic wave propagation. The low Maher number flow around a circular cylinder flow noise numerical prediction, time domain calculation method to obtain the results and the frequency-domain method results and experimental data, the far-field noise time periodic, noise distribution is consistent with the flow pulsation. The numerical results show that this method can consider the distribution of instantaneous characteristics noise, scattering effect and can accurately simulate the non compact boundary.

【学位授予单位】：西北工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB53
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本文编号：1491133