The hydrodynamics and flow structures of a base wing slotted with tip sails in proximity to the ground were studied experimentally in order to investigate the flow control efficiency of wing tip sails in ground effect...The hydrodynamics and flow structures of a base wing slotted with tip sails in proximity to the ground were studied experimentally in order to investigate the flow control efficiency of wing tip sails in ground effect.The experiment was conducted in a towing tank at a Reynolds number 1.5×10^5.The lift and drag forces were measured by a transducer,the velocity fields of the wing tip vortices were measured using a time-resolved particle image velocimetry system(TR-PIV).The tip-sails and ground clearance were both effective in reducing the total drag,the lift coefficients of the tip-sails wings were increased as compared with that of a base wing.The lift-drag ratios of the tip-sails wings were improved obviously in a range of angles of attack from 2°to stalling angle.The tip-sails played more important role in unwinding the concentrated wing tip vortices at higher angle of attack,the intensity of the tip vortices were much weaker than that of the base wing.The development of the wing tip vortices was suppressed as well due to the inhibition of the ground,the downwash speed was reduced and the induced drag was decreased.展开更多
The tip vortices and aerodynamics of a NACA0012 wing in the vicinity of the ground were studied in a wind tunnel.The wing tip vortex structures and lift/drag forces were measured by a seven-hole probe and a force bala...The tip vortices and aerodynamics of a NACA0012 wing in the vicinity of the ground were studied in a wind tunnel.The wing tip vortex structures and lift/drag forces were measured by a seven-hole probe and a force balance,respectively.The evolution of the flow structures and aerodynamics with a ground height were analyzed.The vorticity of tip vortices was found to reduce with the decreasing of the ground height,and the position of vortex-core moved gradually to the outboard of the wing tip.Therefore,the down-wash flow induced by the tip vortices was weakened. However,vortex breakdown occurred as the wing lowered to the ground.From the experimental results of aerodynamics,the maximum lift-to-drag ratio was observed when the angle of attack was 2.5°and the ground clearance was 0.2.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11472169).
文摘The hydrodynamics and flow structures of a base wing slotted with tip sails in proximity to the ground were studied experimentally in order to investigate the flow control efficiency of wing tip sails in ground effect.The experiment was conducted in a towing tank at a Reynolds number 1.5×10^5.The lift and drag forces were measured by a transducer,the velocity fields of the wing tip vortices were measured using a time-resolved particle image velocimetry system(TR-PIV).The tip-sails and ground clearance were both effective in reducing the total drag,the lift coefficients of the tip-sails wings were increased as compared with that of a base wing.The lift-drag ratios of the tip-sails wings were improved obviously in a range of angles of attack from 2°to stalling angle.The tip-sails played more important role in unwinding the concentrated wing tip vortices at higher angle of attack,the intensity of the tip vortices were much weaker than that of the base wing.The development of the wing tip vortices was suppressed as well due to the inhibition of the ground,the downwash speed was reduced and the induced drag was decreased.
基金supported by the National Natural Science Foundation of China(11072142)Shanghai Program for Innovative Research Team in Universities
文摘The tip vortices and aerodynamics of a NACA0012 wing in the vicinity of the ground were studied in a wind tunnel.The wing tip vortex structures and lift/drag forces were measured by a seven-hole probe and a force balance,respectively.The evolution of the flow structures and aerodynamics with a ground height were analyzed.The vorticity of tip vortices was found to reduce with the decreasing of the ground height,and the position of vortex-core moved gradually to the outboard of the wing tip.Therefore,the down-wash flow induced by the tip vortices was weakened. However,vortex breakdown occurred as the wing lowered to the ground.From the experimental results of aerodynamics,the maximum lift-to-drag ratio was observed when the angle of attack was 2.5°and the ground clearance was 0.2.
