Rod-airfoil interaction noise becomes a major issue in some aeronautical applications.The design of four wavy leading edges(WLEs)with varying wavelengths,bioinspired by the tubercles on humpback whales’flippers,aims ...Rod-airfoil interaction noise becomes a major issue in some aeronautical applications.The design of four wavy leading edges(WLEs)with varying wavelengths,bioinspired by the tubercles on humpback whales’flippers,aims to mitigate far-field noise.Among these cases,a reduction in the wavelength is found to be advantageous for noise suppression,with the smallest wavelength case achieving a maximum noise reduction of 1.9 dB.Furthermore,the noise radiation induced by WLEs is suppressed mainly at medium frequencies.The theory of multiprocess aeroacoustics is applied to reveal their underlying mechanisms.The dominant factor is the source cutoff effect,which significantly decreases the source strength on hills.Additionally,spanwise decoherence with phase interference serves as another crucial mechanism,particularly for reducing mid-frequency noise.展开更多
以NACA 65(12)–10独立基准叶片为对象,使用线性传声器阵列和SODIX(SOurce DIrectivity modeling in the cross-spectral matriX)方法对基准叶片前缘噪声指向性分布特征及波浪前缘对叶片前缘噪声的影响进行了实验研究。开发了SODIX数据...以NACA 65(12)–10独立基准叶片为对象,使用线性传声器阵列和SODIX(SOurce DIrectivity modeling in the cross-spectral matriX)方法对基准叶片前缘噪声指向性分布特征及波浪前缘对叶片前缘噪声的影响进行了实验研究。开发了SODIX数据处理程序并进行了数值仿真验证,结果表明:不同指向角下计算结果的最大误差不超过0.26 dB。在半消声室内,利用由31个传声器组成的非均匀分布优化阵列,对NACA 65(12)–10独立基准叶片和仿生学叶片的前缘噪声开展了参数化声学实验。结果表明:在40°~142°指向角测量范围内,基准叶片前缘噪声指向性符合典型偶极子声源特征,峰值在130°指向角附近;随着频率升高,基准叶片前缘噪声指向性产生了显著的“波瓣”现象,频率越高,“波瓣”越多。进一步研究表明:不同波长和幅值的前缘构型都可以有效降低指向角测量范围内的前缘噪声;与波浪前缘的波长相比,波浪前缘的幅值对前缘噪声的影响更为显著,特别是在90°~120°指向角范围内,A30W20叶型的降噪量可达7.71 dB。展开更多
为研究边界条件对三维非定常单圆柱绕流湍流气动噪声的影响,采用大涡模拟并结合Ffowcs Williams and Hawkings声类比方法,对单圆柱近、远场气动噪声辐射特性进行了数值模拟。通过对入流面、出流面、展向侧面以及垂向顶/底面设置不同的...为研究边界条件对三维非定常单圆柱绕流湍流气动噪声的影响,采用大涡模拟并结合Ffowcs Williams and Hawkings声类比方法,对单圆柱近、远场气动噪声辐射特性进行了数值模拟。通过对入流面、出流面、展向侧面以及垂向顶/底面设置不同的边界条件组成4种计算工况,数值模拟结果与文献试验结果比较分析得到:当计算域的入流面、出流面和展向侧面的边界条件设为自由流,而垂向顶面和底面为充分发展的周期性边界时,能够较好地预测声压级频率及其对应峰值,与试验结果吻合较好。进一步分析表明,与其他3种工况的边界条件相比,计算域的入流面、出流面和展向侧面为自由流边界,即流向与展向边界上无声反射的边界条件更适合用于此类气动噪声的数值模拟。本文结论为类圆柱体、多圆柱体或更加复杂的各种柱体结构气动噪声数值模拟提供了一种可行的边界条件设置方法。展开更多
基金supported by the National Natural Science Foundation of China(12322210,12172351,92252202,and 12388101)the Fundamental Research Funds for the Central Universities.
文摘Rod-airfoil interaction noise becomes a major issue in some aeronautical applications.The design of four wavy leading edges(WLEs)with varying wavelengths,bioinspired by the tubercles on humpback whales’flippers,aims to mitigate far-field noise.Among these cases,a reduction in the wavelength is found to be advantageous for noise suppression,with the smallest wavelength case achieving a maximum noise reduction of 1.9 dB.Furthermore,the noise radiation induced by WLEs is suppressed mainly at medium frequencies.The theory of multiprocess aeroacoustics is applied to reveal their underlying mechanisms.The dominant factor is the source cutoff effect,which significantly decreases the source strength on hills.Additionally,spanwise decoherence with phase interference serves as another crucial mechanism,particularly for reducing mid-frequency noise.
文摘为研究边界条件对三维非定常单圆柱绕流湍流气动噪声的影响,采用大涡模拟并结合Ffowcs Williams and Hawkings声类比方法,对单圆柱近、远场气动噪声辐射特性进行了数值模拟。通过对入流面、出流面、展向侧面以及垂向顶/底面设置不同的边界条件组成4种计算工况,数值模拟结果与文献试验结果比较分析得到:当计算域的入流面、出流面和展向侧面的边界条件设为自由流,而垂向顶面和底面为充分发展的周期性边界时,能够较好地预测声压级频率及其对应峰值,与试验结果吻合较好。进一步分析表明,与其他3种工况的边界条件相比,计算域的入流面、出流面和展向侧面为自由流边界,即流向与展向边界上无声反射的边界条件更适合用于此类气动噪声的数值模拟。本文结论为类圆柱体、多圆柱体或更加复杂的各种柱体结构气动噪声数值模拟提供了一种可行的边界条件设置方法。
