Experimental and numerical studies on noise radiated by flow past a rectangular two-dimensional deep cavity with passive control are conducted to research the mechanism of cavity noise reduction at low Mach numbers. The clean cavity has a depth-to-length ratio of 1.5 and a width-to-length ratio of 3. The passive control method is used by slanting the front and rear walls. Using acoustic microphones, both the surface noise and far-field noise are tested in an aeroacoustic wind tunnel. It is observed that the slanted rear wall can suppress the noise effectively, but for the slanted front wall, the tones will be enhanced at some velocities. Numerical simulation is conducted to reveal the mechanism. The results reveal that the slanted rear wall can reflect the unsteadiness back to the shear layer and break up the vortices in it. These vortexes will diffuse after impacting the rear wall and prevent the perturbation from moving deeper, which brings a stable flow field into the cavity. As for the slanted front wall, the vortices will be enlarged and become accelerated in the shear layer, which makes the impingement of it to the rear wall more intense, thus leading to an increase in the noise level.

进行了通过二维二维矩形深腔无源控制的流体辐射噪声的实验和数值研究，以研究低马赫数腔噪声的减小机理。清洁腔的长宽比为1.5，宽长比为3。通过倾斜前壁和后壁，可以使用被动控制方法。使用声学麦克风，可以在航空声学风洞中测试表面噪声和远场噪声。观察到倾斜的后壁可以有效地抑制噪声，但是对于倾斜的前壁，在某些速度下音调会增强。进行了数值模拟以揭示其机理。结果表明，倾斜的后壁可以将不稳定性反射回剪切层并破坏其中的涡流。这些涡流在撞击后壁后会扩散，并防止扰动向更深处移动，从而将稳定的流场带入空腔。至于倾斜的前壁，涡流将在剪切层中扩大并加速，这使得它对后壁的冲击更强烈，从而导致噪声水平的增加。