三维圆柱声辐射特性数值模拟研究

Numerical simulation of the acoustic radiation characteristics of a three dimensional cylinder

了解流噪声产生机理及其特性,对于正确预测以及降低海洋结构物噪声具有重要意义。为了详细分析圆柱绕流的声辐射特性,对三维圆柱绕流噪声进行了数值模拟研究。首先,采用大涡模拟(large eddy simulation,简称LES)方法计算了非定常流场特征,结果与试验数据对比吻合良好;接着,基于流场结果利用FW-H方程以面积分法预测远场噪声,其总声压级与试验误差在5%以内,验证了方法的有效性;随后,对圆柱绕流噪声的辐射特性进行了分析,发现关于圆柱对称的各点总声压级相等,表明圆柱绕流声场具有对称性,与来流方向垂直、平行的各点声压级存在峰值,峰值频率分别对应于圆柱绕流涡脱落频率和涡脱落频率的两倍;最后,在亚临界雷诺数范围内分析了不同雷诺数对圆柱绕流噪声的影响。分析结果将为后续降噪研究提供一定参考。

Understanding the generation mechanism and characteristics of flow noise is of great significance for accurately predicting and reducing the noise of offshore structures.To analyze the acoustic radiation characteristics of the flow around a three-dimensional cylinder in detail,a numerical simulation study on the flow noise of a three-dimensional cylinder was carried out.First,the unsteady flow field characteristics were calculated using the large eddy simulation(LES)method,and the results were compared with experimental data,showing good agreement.Then,based on the flow field results,the far-field noise was predicted using the FW-H equation by the area integral method,and the overall sound pressure level had an error within 5%compared to the experimental data,verifying the effectiveness of the method.Subsequently,the radiation characteristics of the flow noise around the cylinder were analyzed,and it was found that the overall sound pressure levels at symmetric points around the cylinder were equal,indicating that the sound field of the cylinder flow has symmetry.There are peaks in the sound pressure levels at points perpendicular and parallel to the flow direction,with the peak frequencies corresponding to the vortex shedding frequency of the cylinder flow and twice the vortex shedding frequency,respectively.Finally,the effect of different Reynolds numbers on the cylinder flow noise within the subcritical Reynolds number range was analyzed.The analysis results will provide some reference for subsequent noise reduction research.