Study on wake flow characteristics of delta wing based on particle image velocimetry

Particle image velocimetry (PIV) is a key method for analyzing complex transient flow fields. To reveal the influence of small angles of attack and low Mach numbers (Ma) on wing wakes, a wake measurement scheme for the NACA0012 airfoil delta wing based on PIV was designed. Experiments were conducted in a 0.6 m continuous wind tunnel under conditions covering Ma from 0.3 to 0.6 and angles of attack from −4° to 4°. Wake velocity fields were obtained via PIV, and combined with the Q-criterion, calculations of shear layer thickness and analysis of vortex structure evolution were completed. Results revealed that the wake vortices exhibit regular periodic distribution at negative angles of attack. When the positive angle of attack exceeded 3°, the disorder of vortex structures rose, and the shear layer thickened significantly due to flow separation. As the Mach number increased, vortex breakdown and diffusion intensified; at Ma=0.6, due to enhanced compressibility, vortex oscillation and breakdown became more severe, and the fluctuation amplitude of the shear layer increased. This study acquires key velocity information via a self-built PIV system, revealing the influence mechanisms of small angles of attack and low Mach numbers on wake flow, providing quantitative data in the field of aerodynamic characteristics of subsonic delta wing wakes at low angle of attack and offering technical support for aerodynamic optimization design of airfoils.