In the galloping process of iced bundle conductor,the coupling relationship of conductor's torsional vibration and transverse vibration may cause unsteady motion. Based on the coupling movement of section model of transmission line,the expression of aerodynamic parameters of transmission line on unsteady state was derived,which was numerically simulated.The simulated results of aerodynamic parameters were verified by using the existing wind tunnel data. The simulation of unsteady state aerodynamic parameter...