关键词: 遮檐式空腔, 侧壁效应, 分离涡模拟, 流声耦合, 风洞试验

Abstract: Overhanging lip cavity flow widely exists in engineering, but the influence mechanism of the side wall of the finite-width overhanging lip cavity on the flow evolution and fluctuating pressure characteristics is not clear. In this paper, combined with wind tunnel test and detached eddy simulation ( DES ), the influence of the side wall on the spatial distribution and power spectral density characteristics of the fluctuating pressure energy of the overhanging lip cavity under the wind speed of 40 m/s-70 m / s is studied, and the flow-acoustic coupling mechanism of the overhanging lip cavity is analyzed simultaneously. The results show that the spatial distribution of fluctuating pressure energy is dispersed at low wind speed, and the contribution of near-wall region is obvious. As the wind speed increases, the low-frequency energy gradually concentrates to the middle of the cavity. The power spectral density of fluctuating pressure in the central section shows a significant narrow-band peak at 300-450 Hz. The peak frequency increases with the increase of wind speed, and the growth rate slows down at high wind speed. High-frequency characteristic peaks of 1220-1240 Hz appear at the measuring points on the side wall. Affected by the side wall surface, the vortex structure near the cavity wall is broken into small-scale vortices, which induces high-frequency fluctuating pressure on the side wall surface. The self-sustaining oscillation of the cavity and the acoustic mode have flow-acoustic coupling, which excites the high-frequency discrete peak of the fluctuating pressure. It provides a theoretical basis for the design and oscillation suppression of a finite-width overhanging lip cavity.

Key words: overhanging lip cavity, sidewall effect, detached eddy simulation, flow-acoustic coupling, wind-tunnels