Fluid-structure Interaction Of Elastic Thin Wing With One Fixed End And One Bearing Supported End

With the development of major national projects such as solar-powered airplane,flexible wings have been extensively studied in experiments and numerical simulations in recent years.In this paper,a flexible thin NACA0012 airfoil with an aspect ratio of 9 is designed.Through experimental fluid mechanics methods,instruments such as sixcomponent force balance,pressure sensors,hot wire,Bragg fiber grating and particle image velocimetry technology are used to study the aerodynamic characteristic,vibration and flow fields of one fixed end and one bearing supported end wing.And the results of that were also compared with the two fixed end wing results.This experiment focuses on the conditions where the angle of attack ? is 0°-90°,and the Reynolds numbers are 9.6×10~4,1.28×10~5 and 1.5×10~5.According to the relationship between the lift coefficient and the angle of attack,the angle is divided into three regions.When ? is between 0°?4°,it is the small-angle region.The lift coefficient changes linearly with ?.When ? is between 4°?12°,it is the stall-angle region,and the lift coefficient tends to drop sharply.The one fixed end and one bearing supported end wing stalls ahead than the rigid wing.When ? is between 12°?90°,it is the large-angle region.In this region when ? increases to 50°,the lift coefficient continues to increase.When the angle increases further,the lift coefficient decreases and approaches a minimum at 90°.Through the research of particle image velocimetry,it is found that the wing has different flow states in three regions.The flow on the wing surface does not separate in the small-angle region.The wing surface flow field begins to separate and vortex shedding also occurs in the stall-angle region.The flow field on the wing surface completely separates in the large-angle region,and the width of the wake continues to increase as the angle increases.The flexible wing vibrates with deformation of bend and twist under the action of the flow.Compared with the two fixed end wing,the flutter phenomenon does not occur with one fixed end and one bearing supported end wing.The vibration is periodic vibration with a large amplitude but is not continuous.According to the time-history of displacement and the probability density function of the pulsating displacement,it is found that the periodic vibration is larger in the stall-angle region ?=8° than in the largeangle region ?=40°.Besides,an analysis of the power spectral density function of the flow field velocity and pressure signal reveals that there is no vortex shedding in the small-angle region.And the vibration of the wing is bending vibration.Because the wing is subjected to additional stiffness and additional mass under the action of the fluid,the vibration frequency increases with the increasing wind speed.In the stall-angle region,although vortex shedding occurs,the correlation between the displacement of the wing and the velocity of the flow field is very small.In this region,the vibration is still bending vibration.In the large-angle region there is obvious vortex shedding.In this region,the wing vibration is also affected by the vortex shedding.The displacement signal of the wing is highly coherent with the flow field velocity.