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首页> 外文期刊>Applied Acoustics >Numerical investigation on radiation characteristics of discrete-frequency noise from scarf and scoop aero-intakes
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Numerical investigation on radiation characteristics of discrete-frequency noise from scarf and scoop aero-intakes

机译：围巾和铲子进气口离散频率噪声辐射特性的数值研究

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Numerical studies have been carried out to investigate the detailed geometrical effects of full three-dimensional aero-intakes on the radiation of the discrete-frequency rotor-stator interaction noise. The near-field acoustic radiation characteristics and the far-field directivity patterns from the scarf and scoop aero-intakes with three different scarf/scoop angles are quantitatively analyzed and compared. The near-field predictions were obtained by solving the linearized Euler equations with computational aeroacoustic techniques consisting of high-order finite difference scheme, non-reflecting boundary conditions, overset grids and parallel computational methods. For the prediction of far-field directivity pattern, the Kirchhoff integral method was applied. By comparing the directivities of discrete-frequency noise radiating from the scarf and the scoop aero-intakes with that from an axisymmetric aero-intake, it is shown that the 7 dB noise reduction at downward peak radiation angle can be achieved by using the scoop aero-intake with scoop angle of 15°, and the 5 dB noise reduction by the scarf aero-intake with the scarf angle of 15°. The scattering of the radiating acoustic wave by the background mean flow around the aero-intakes shifts the peak lobe radiation angle toward ground and increases the amplitude of the acoustic pressure compared with the cases without mean flow effect. Overall, the scoop aero-intake was found to be more effective than the scarf and the axisymmetric aero-intakes in view of the lower noise radiation toward ground.
机译：已经进行了数值研究，以研究完整的三维进气口对离散频率转子-定子相互作用噪声辐射的详细几何影响。定量分析和比较了来自具有三个不同的围巾/铲斗角度的围巾和铲子进气口的近场声辐射特性和远场方向性图。通过使用包括高阶有限差分方案，非反射边界条件，重设网格和并行计算方法的计算航空声学技术求解线性化的欧拉方程，可以获得近场预测。为了预测远场方向图，采用了基尔霍夫积分法。通过比较围巾和勺状进气口的离散频率噪声与轴对称进气口的离散频率噪声的方向性，可以看出，通过使用勺状进气口，可以在向下峰值辐射角处将噪声降低7 dB。 -铲形角度为15°的进气口，而领巾角度为15°的围巾式进气口降低了5 dB的噪音。与没有平均流效应的情况相比，由周围进气口的背景平均流对辐射声波的散射使峰值波瓣辐射角向地面移动，并增大了声压的幅度。总体而言，鉴于对地面的噪声辐射较低，因此，瓢式进气口比围巾和轴对称进气口更有效。

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