## 1 Introduction
The study examines the role of the velocity profile shape on the instability characteristics and the nature of the large-scale vortical structures shed downstream of the bubble and enables identification of the structure of the instability mechanism and the characteristic structure of the resultant turbulent spots. The research on the effect of turbulence intensity on airfoil is mostly concentrated on the turbine blade and low-speed airfoil. [PERSON] [10] found that the free-stream turbulence intensity modify the transition and separation processes of the suction side boundary layer of a highly loaded low pressure turbine blade through experiment. The stall characteristics of airfoil S1223 has been investigated by [PERSON] [20] at low Reynolds numbers, implying that the smaller integral length under 4.1% turbulence intensity delays the boundary layer separation on the suction surface. [PERSON] [21] conducted an experiment of NACA0015 immersed in two grid generated homogenous flows. [PERSON] [22; 23] investigated NACA0018 under varied Reynolds numbers and turbulence intensities to find that increasing freestream turbulence intensity results in earlier transition and reattachment, contributing to an overall decrease in separation bubble length. [PERSON] [24] established an extensive database of surface oil flow measurements of seven airfoils that represents a wide range in behavior at low Reynolds numbers. [PERSON] and [PERSON] [25; 26] carried out an experiment on NACA0012 under varied turbulence intensities at Re =5,300 to validate their numerical simulation. [PERSON] [27] studied the aerodynamic characteristics of unsymmetrical airfoil at various turbulence intensities through experiments and found that the lift coefficient increases with the increase of turbulence intensity. The results also reveal that the flow featuring turbulence can effectively delay the stall characteristicsof an airfoil by attaching the flow over the airfoil for an ex-tended region. The influence of freestream turbulence intensity (FSTI) level on the structure and dynamic properties of a laminar separation bubble has been experimentally studied by [PERSON] [28]. He concluded that the bubble length and height reduction at a high FSTI level with a fixed Reynolds number are due to the higher amplitude of velocity fluctuations penetrating into the separating boundary layer. Conversely, the Reynolds number significantly influences the time-mean boundary layer structure at separation. The existing research on the influence of the turbulence intensity on airfoils have been conducted with Reynolds numbers between 100,000 and 1200,000, but the work under 100,000 Reynolds number is lacking. Meanwhile the TeDP UAV is a new topic, which brings about new problems in airfoil design. It is necessary to carry out further research on aerodynamic performance of airfoil in the flow with great changes of Reynolds number and turbulence intensity. Therefore, facing the unsteady jet flow generated by the TeDP system during taking off, the aerodynamic performance of airfoil under varied Reynolds numbers and turbulence intensities is studied by using the commercial software FLUENT based on the computational fluid dynamics (CFD) method. The numerical method applied in this paper is verified by comparing the pressure distribution, the lift and drag coefficient of the NACA0012 airfoil with different turbulence intensities and Reynolds numbers. The effects of turbulence intensity and Reynolds number on the aerodynamic performance of airfoil and flow field characteristics are studied. The mechanisms of earlier transition in the boundary layer, the relationship between the evolution of laminar separation bubble and Reynolds number are presented.