Numerical Simulation And PIV Experimental Study On Flow Characteristics Of High-Lift System

With the development of aircraft design technology,the high-lift system plays an increasingly crucial role in the aircraft.However,because of the complexity of the flow field,it is very challenging to determine the proper configuration of high-lift system and the calculating methods for high-lift system by numerical simulation are extremely limited.To achieve accurate measurement for complex flow field is still a tough task since the serious shortage in measurement technology,especially in measurement for slot of highlift system.Moreover,despite the fact that the development of particle image velocimetry(PIV)offers great advantages for flow field measurement of the high-lift system,unfortunately,it still suffers from the drawbacks that the slot in high-lift system is too small and it is hard to arrange for the optical path.Therefore,measurements in PIV technology which are suitable for the flow field of the high-lift system still have much room to improve.In this paper,the numerical simulation of the high-lift system is carried out.Based on the structural grid,the two-dimensional Reynolds average N-S equation is used as the governing equation,and the turbulence model is solved as the S-A model,which verifies the accuracy of the numerical simulation.To solve the problem of light in PIV measurement of high-lift system,a PIV light-distribution method and a set of devices suitable for flow field measurement of high-lift system is designed in this paper.According to the principle of light splitting and reflection,the laser can illuminate the area under test at the same time along the two directions of X and Y,and completely illuminate the area under test.The experiments are carried out with three-element high-lift airfoil in low-speed wind tunnel and the influence of the flap and slat gap parameters on the flow field is studied by applying this method to the flow field measurement of the high-lift system.The results have verified the feasibility of the designed PIV light distribution method and the device.Combined with the experimental results and numerical calculations,the influence of the parameters in the flaps and crevices on the aerodynamic characteristics of high-lift system and its mechanism are analyzed.The results show that for the parameters of the flap seam,the value of the slit width and the overlap amount can be increased within a certain range,which can effectively improve the aerodynamic characteristics of the high-lift system and increase the lift increment of the airfoil at the medium and small angle of attack.However,the excessive seam parameters would affect the mixing effect of the jet and main wing boundary layer flow,which could result in a rapid attenuation of the jet that can directly affects the control of the jet flow separation on the trailing edge of the flap.Similarly,changing the parameters of the slat would create similar problems.