Lagrangian analysis of mass transport and its influence on the lift enhancement in a flow over the airfoil with a synthetic jet

The mass transport and lift enhancement in flows over the NACA0015 airfoil with a synthetic jet (SJ) are studied numerically using Lagrangian coherent structures (LCSs). Trajectories of synthetic particles belonging to 9 different groups in a vicinity of the airfoil are tracked to analyze the transport. The influence of mass transport on the aerodynamic performance of the airfoil and on the surface pressure coefficient distribution is studied. The difference in transport properties for the airfoil with and without the SJ is analyzed to understand the reasons of the lift enhancement. The results show that the LCSs could be successfully used to describe transport and mixing in the complex flows in the blowing and suction phases. More, the fluid originating in the upper reaches is continuously sucked out of the flow field in the suction phase, then the jet injected by the jet slot moves to the lower reaches of the jet slot in the blowing phase. Compared with the original airfoil, the controlled airfoil could bring about the fluid adhering to the surface moving constantly and the lift coefficient improved apparently, whether in the suction or blowing phase. Resulting from the SJ, the high momentum fluid is injected into the flow field near the airfoil. Therefore, the boundary layer separation point of the airfoil is pushed downstream, and the area of the flow separation zone is greatly reduced. Generally, utilizing LCS to study mass transport process can provide a new perspective for the study of the SJ. (C) 2019 Elsevier Masson SAS. All rights reserved.