This paper investigates self-excited oscillation within a slat cove and the flowfield parameters involved in selection of the main oscillation mode. Aeroacoustic experiments are described for aerodynamic noise characteristics on the leading-edge slat of a two-dimensional three-element high-lift configuration. Different geometrical settings are tested at varying angles of attack. A numerical simulation method is used as an auxiliary tool to analyze the flowfield. Based on previous research results and the experimental results obtained in this paper, a ratio of $L_v/(\delta \cdot K_v)$ is proposed to evaluate the main mode of self-excited oscillation, where $L_v$ is the shear-layer length within the slat cove, $\delta$ is the boundary-layer thickness near the point of separation, and $K_v$ is the ratio of average vortex convection velocity along the shear layer to the maximum velocity in the shear layer near the cusp. The relationship between the aforementioned ratio and the main mode of oscillation is verified by far-field noise data for a high-lift configuration with different geometrical settings. As the slat translation along the chordwise direction of the main wing increases, the ratio $L_v/(\delta \cdot K_v)$ also increases; and the main mode of self-excited oscillation switches from mode II to a transition phase, and then to mode III.

本文研究了板条湾内的自激振荡以及选择主振荡模式所涉及的流场参数。描述了二维三元素高升力结构的前沿板条上的气动噪声特性的航空声学实验。在不同的迎角下测试不同的几何设置。数值模拟方法用作分析流场的辅助工具。根据以前的研究结果和本文获得的实验结果，比率为${\mathrm{大号}}_v/（\delta \cdot {ķ}_v）$ 提出了评估自激振荡的主要模式，其中 ${\mathrm{大号}}_v$ 是板条湾内的剪切层长度， $\delta$ 是分离点附近的边界层厚度，并且 ${ķ}_v$是沿剪切层的平均涡流对流速度与尖端附近剪切层中的最大速度之比。对于具有不同几何设置的高升程配置，通过远场噪声数据验证了上述比率与主要振荡模式之间的关系。随着沿主翼弦向的板条平移量增加，该比率${\mathrm{大号}}_v/（\delta \cdot {ķ}_v）$也增加了；自激振荡的主模式从模式II切换到过渡阶段，然后再切换到模式III。