矩形腔体流场模拟及噪声研究

NUMERICAL SIMULATION AND NOISE ANALYSIS OF A FLOW OVER AN OPEN CAVITY

用大涡模拟方法对低速湍流引起的矩形腔体内流动进行了模拟,并应用FW-H声学类比方程分析了由流动诱发的气动噪声。数值模拟观察到了涡结构的脱体及腔体内部的自激振荡过程,通过分析得出了由流动诱发噪声的声压-频率曲线。研究发现在流速30 m/s时,流动噪声声压级在60 dB以下,348.48 Hz及其高次谐波是噪声的主要来源,流场与声场表现出耦合关系,辐射声场具有明显的方向性。腔体噪声的风洞实验研究得到了与数值模拟吻合的结果。

The flow mechanism of the shearing flow over an open cavity is investigated using the Large Eddy Simulation （LES） method. After the flow field is acquired, the FW-H analogy is applied to compute the flow induced noise. The large scale shedding as well as self-oscillation in the cavity is observed. Tile sound pressure level vs. frequency of noise induced by flow is obtained. With the flow velocity as 30 m/s, the sound pressure of flow-induced noise is under 60 db. The noise frequency of 348.48 Hz and its harmonics are the main source of noise. The coupling of the acoustic and vorticity fields as well as the direction of acoustic fields are found. The noise caused by the flow is tested in a wind tunnel and the results agree well with the simulations.