Study of self-excited oscillations in the flow field of a cavity with two opposing louvers

Self-excited oscillations can occur when a flow passes over a louvered cavity, leading to engineering problems such as vibration and noise. Although studies on single-louver cavities have achieved notable progress, the flow physics in multi-louver cavities commonly encountered in engineering applications remains insufficiently understood. In this work, numerical simulations are performed to investigate self-excited oscillations in the flow over a cavity equipped with two opposing louvers. The results show that each louver exhibits self-excited oscillations similar to those in single-louver configurations, and their interaction induces low-amplitude oscillations within the cavity. A stage-switching phenomenon is identified when the louver position is varied. This stage switching is caused by a change in the vorticity accumulation rate around the louver, which is governed by the inner-side flow direction. When the inner-side flow is directed downstream, vorticity accumulates more rapidly around the louver (i.e., spanwise vortices form faster), resulting in a pronounced increase in the oscillation frequency. In addition, the downstream louver is found to exhibit larger oscillation amplitudes.