Abstract: For the exploration on principle of slat noise investigation on the unsteady flow of a leading edge slat of a multi-element airfoil under different conditions with unsteady pressure transducers placed around the slat cove region is performed in the two-dimensional testing section of a NF-3 wind tunnel at Northwestern Polytechincal University.It analyzes the relationship between the flow unsteadiness and the Reynolds number,angle of attack,parameters of slat and flap (deflecting angle, gap, overlap).Through comparison,the study demonstrates that the Reynolds number,slat position,flap position and angle of attack can all influence the flow unsteadiness of the slat cove.It also reveals the change and trend of the vortex in the slat cove region and the front of the main wing region,its influence on the flow over the airfoil,as well as the cause of the slat noise.The study is of considerable significance to the investigation of noise source and noise reduction of multi-element airfoils.

Key words: multi-element airfoil, slat, dynamic pressure, unsteady flow, noise