Abstract: Influence of plasma actuators on the flow separation control of NACA 0015 airfoil was investigated in an open-circuit low-speed wind tunnel.Particle Image Velocimetry(PIV)technology was applied to visualize the modification of the flow structure over the airfoil by the plasma actuators.Lift and drag were measured by a five-component strain gauge balance to investigate the separation control effect of the actuator voltage and excitation frequency.The results show that the leading-edge plasma actuators are effective in controlling the flow separation over the airfoil at low wind speeds.The maximum lift coefficient and stall angle are increased by 11%and 6 deg respectively at the free-stream velocity of 20m/s.However,at a given flow state,there exists threshold values for both the actuator voltage and excitation frequency on the actuators.The threshold values are different with the changing attack angles.At the higher attack angles,the plasma actuator's authority must be increased due to the much stronger flow separation on the airfoil.
Abstract: For important bridges,it is required by the Wind-resistant Design Code for Highway Bridges that a reasonable basic design wind speed be selected from the results obtained either by re-observing the basic design wind speed at bridge site or by referring to the samples of measured wind speed.In this paper,the design wind speed of Xiamen-Zhangzhou Cross-sea Bridge corresponding to different return period was calculated using three extreme value distribution schemes with the extreme value of the wind speed and its corresponding wind direction standard value taken from 360 months' 10-minute-time-interval observation by Xiamen Observatory and Longhai Weather Bureau.It is obtained that the 100-year return period expected wind speed at the bridge site is 35.8m/s,lower than 39.7m/s as given in the Code.