基于Kirchhoff方法的亚声速平面混合层主涡对并声场分析

为拓展主涡对并气动声场计算分析方法研究,针对亚声速平面混合层主涡对并流动,采用直接数值模拟(DNS)方法求解获取近场声源,利用二维Kirchhoff频域法和时域法外推声辐射远场,并应用Kirchhoff频域法对主涡二次对并声辐射特征进行分析。研究结果表明:Kirchhoff频域法和时域法具有一定差异性,但与主涡对并直接声计算结果对比,显示二者计算精度相当且均具有较高的精确性。通过Kirchhoff频域法应用分析,清晰揭示出主涡二次对并各声模态与主涡卷起、对并过程的对应相关性,利用频域法这种良好的计算分析性能,本文进一步研究了混合层入口扰动相位差对涡并声场的影响,展现出主导声波在声场中的重要作用。

Analysis of Acoustic Field of Primary Vortex Pairing in Subsonic Plane Mixing Layers Using Kirchhoff Method

In order to expand the calculation and analysis of an acoustic field generated by vortex pairing, the subsonic planar mixing layer vortex pairing is studied with numerical method. Direct numerical simulation (DNS) is employed to extract the acoustic source, the two-dimensional frequency domain and time domain Kirchhoff methods are applied to extrapolate the far-field radiated sound, while the frequency domain method is employed to investigate the sound radiation from the twice vortex pairings. The frequency domain and time domain Kirchhoff methods are different in some degree, but the computation results compared with the DNS show that they reach a similar high order of accuracy. An analysis with frequency domain Kirchhoff method reveals clearly that each acoustic mode of the twice vortex pairings corresponds to the vortex rolls and pairings respectively. Using the frequency domain method's good performance of computation and analysis, this paper further studies the influence of inflow instability waves with different phases on the acoustic field of vortex pairings, and exhibits that the dominant mode plays an important role in the acoustic field.