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首页> 外文期刊>Multiscale modeling & simulation >MULTISCALE ANALYSIS OF SPECTRAL BROADENING OF ACOUSTIC WAVES BY A TURBULENT SHEAR LAYER
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MULTISCALE ANALYSIS OF SPECTRAL BROADENING OF ACOUSTIC WAVES BY A TURBULENT SHEAR LAYER

机译：湍流剪切层的声波光谱扩展的多尺度分析

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摘要

We consider the scattering of acoustic waves emitted by an active source above a plane turbulent shear layer. The layer is modeled by a moving random medium with small spatial and temporal fluctuations of its mean velocity, and constant density and speed of sound. We develop a multiscale perturbative analysis for the acoustic pressure field transmitted by the layer and derive its power spectral density when the correlation function of the velocity fluctuations is known. Our aim is to compare the proposed analytical model with some experimental results obtained for jet flows in open wind tunnels. We start with the Euler equations for an ideal fluid flow and linearize them about an ambient, unsteady inhomogeneous flow. We study the transmitted pressure field without fluctuations of the ambient flow velocity to obtain the Green's function of the unperturbed medium with constant characteristics. Then we use a Lippmann-Schwinger equation to derive an analytical expression of the transmitted pressure field, as a function of the velocity fluctuations within the layer. Its power spectral density is subsequently computed invoking a stationary-phase argument, assuming in addition that the source is time-harmonic and the layer is thin. We finally study the influence of the source tone frequency and ambient flow velocity on the power spectral density of the transmitted pressure field and compare our results with other analytical models and experimental data.
机译：我们考虑由平面湍流剪切层上方的有源源发射的声波的散射。该层由移动的随机介质模型，其平均速度小的空间和时间波动，以及恒定的密度和声音速度。当已知速度波动的相关函数时，我们为由层发射的声压场进行多尺度扰动分析，并导出其功率谱密度。我们的目的是将提议的分析模型与在露天隧道中的喷射流动获得的一些实验结果进行比较。我们从欧拉方程开始，以获得理想的流体流动，并将它们线性化为环境，不稳定的不均匀流动。我们研究了透射的压力场，而不会对环境流速的波动进行波动，以获得具有恒定特性的未受干扰介质的绿色功能。然后，我们使用Lippmann-Schwinger方程来导出透射压力场的分析表达，作为层内的速度波动的函数。随后计算其功率谱密度调用静止相位参数，假设源是时间谐波，并且该图层很薄。我们终于研究了源音频率和环境流速对传输压力场的功率谱密度的影响，并将我们的结果与其他分析模型和实验数据进行比较。

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