Suppression of flow-induced resonant cavity noise using mass flow injection

The mechanism of flow-induced cavity noise control by vertical mass flow injection at the leading edge of the opening and parallel mass flow injection at the front wall surface is revealed through numerical simulation, and the law of peak noise reduction and total noise reduction by the injected flow velocities under the influence of multiple parameters is studied. The vertical mass flow injection at the leading edge of the opening lifts shear layer to avoid the impact of vortex on the trailing edge of the opening and suppress the noise pulsation pressure peak of the flow-induced cavity. In a certain range, the higher the injected flow velocity, the greater the peak reduction of the flow-induced cavity noise, but the lift in the low-frequency caused by the mass flow injection will also be higher, resulting in the total sound pressure level first decreases and then increases. After optimization, the peak noise reduction and total noise reduction can reach 15dB and 9.5dB, respectively. The parallel injection of mass flow into the front wall of the opening can avoid vortex shedding by strengthening the stability of the shear layer at the opening and achieve the purpose of suppressing the flow-induced cavity noise. When the entrance area is larger than two-third of the front wall area, not only the peak value of flow-induced cavity noise can be significantly reduced, but also the rise of noise in other frequency band can be well restrained, and the noise reduction effect of total sound pressure level is obvious. When the mass flow injection velocity is 0.5 times of the incoming flow velocity, the peak and total noise reduction of the pulsating pressure can reach 18dB and 15.4dB, respectively.