Analysis of Flow Conditions in Freejet Experiments for Studying Airfoil Self-Noise
Analysis of Flow Conditions in Freejet Experiments for Studying Airfoil Self-Noise
复制标题
研究翼型自噪声的自由喷射实验中的流动条件分析
作者：
S. Moreau;M. Henner;G. Iaccarino;Meng Wang;M. Roger
在自由喷射消声风洞中，在翼弦雷诺数为1.2 £ £105的受控扩散翼型上收集了一组新的平均壁压数据。通过对实验数据与雷诺平均Navier-Stokes（RANS）数值模拟结果的比较，发现在自由气流中存在明显的斜流场和压力载荷差异，表明存在明显的喷流干扰效应，为了分析这些影响，对实验气流条件进行了基于RANS的系统计算流体动力学研究，定量分析了喷流宽度对气动载荷和气流特性的影响。当喷流宽度与翼型的前缘湿润面积相比不是足够大时，翼型的压力分布比孤立翼型的压力分布更接近于叶栅的压力分布。翼型升力显著降低。考虑到实际的风洞装置，无需进一步的经验攻角修正，就可恢复翼型上的壁压分布。这些喷流干扰效应可能是造成翼型自噪声的一些早期实验和计算研究之间的差异的原因。在将来的噪声计算中应考虑这些因素，以确保准确模拟实验气流条件。
A new set of mean wall pressure data has been collected on a controlled diffusion airfoil at a chord Reynolds number of 1.2 £ £105 in a freejet anechoic wind tunnel. Comparisons of the experimental data with Reynoldsaveraged Navier‐ Stokes (RANS) simulationsin freeairshow signie cant e owe eld and pressure loading differences, indicatingsubstantialjetinterferenceeffects.Toanalyzetheseeffects,asystematicRANS-basedcomputationale uid dynamicsstudyoftheexperimentale owconditionshasbeencarriedout,whichquantie esthestrongine uenceofthe e nite jet (nozzle) width on the aerodynamic loading and e ow characteristics. When the jet width is not sufe ciently large compared to the frontal wetted area of the airfoil, the airfoil pressure distribution is found to be closer to the distribution on a cascade than that of an isolated proe le. The airfoil lift is signie cantly reduced. Accounting for the actual wind-tunnel setup recovers the wall pressure distribution on the airfoil without further empirical angle-of-attack corrections. These jet interference effects could be responsible for the discrepancies among some earlier experimental and computational studies of airfoil self-noise. They should be accounted for in future noise computations to ensure that the experimental e ow conditions are simulated accurately.