Experimental study on Aerodynamic Characteristics by Different Surface Roughness of Large-Diameter Conductors

The aerodynamic characteristic for the conductor structure of overhead lines is very sensitive to the surface roughness. A wind tunnel test with a rigid model of surface pressure measurement was carried out for typical large-diameter circular wire conductors, trapezoidal wire conductors, and equal-diameter smooth cylinders. The surface pressure characteristics of conductors and cylinders with the Reynolds number, the characteristics of wake vortex based on pressure distribution, the Reynolds number transition zone of the conductor in uniform flow field, and the wake vortex frequency and Strouhal number were studied. A method for determining the aerodynamic coefficient of the structure based on the wind tunnel test for pressure-test was proposed. And the following conclusions were obtained:1) The distribution of the mean wind pressure coefficients along the circumferential direction is studied, according to which the four zones are divided: pressure zone(positive pressure zone), increasing pressure zone(negative pressure zone), decreasing suction zone, stable suction zone. 2) The maximum mean suction coefficient is inversely proportional to the drag coefficient, so the drag force can be decreased by increasing the maximum mean suction coefficient, which provides a new idea for the development of low-wind-pressure conductors. 3) About the critical Reynolds number, smooth cylinder > trapezoidal-wire conductor> round-wire conductor. 4) Considering the design wind speeds of transmission line in China mostly between 25m/s-39m/s, the drag coefficient is smaller than 0.8 based on the research in this paper, which indicates the drag coefficient 1.2 in code for overhead transmission line of China is overestimated.