Numerical Simulation of Aerodynamic Forces of ACSR Conductor

The aerodynamic characteristics of ACSR conductor with the large section were simulated with the fluid dynamics software in this paper. The slightly compressible viscous fluid and the Spalart-Allmaras turbulence model were used to modify the wind around the conductor. The numerical simulation results with the existing test results were compared and the effect of the roughness of the conductor on the aerodynamic characteristics was investigated. As the Reynolds number increases, the steady-state drag coefficients of the large section ACSR conductor decrease and tends to a stable value. The drag and lift coefficients decrease obviously in the range of 20000 to 40000 for the Reynolds number. The fluctuant lift coefficients of smooth boundary conductor are always larger than that of rough boundary model. Among the different mechanical vibration phenomena in high-voltage electrical overhead transmission lines, wind-excited oscillations of the conductors constitute a major issue. The most common of these vibrations are those generated by vortex shedding in the frequency range of approximately 2-50 Hz, corresponding to wind speeds of 1-10 m/s. Although such vibrations are barely perceptible due to their low amplitudes, they are, however, extremely important since they may lead to conductor fatigue at the positions of high-strain concentration. The determination of the aerodynamic coefficients of the conductors is necessary to estimate the vibration of overhead conductor and to ensure the reliability of the transmission lines (1). At the beginning of the last century, a lot of research activities had been conducted and a series research results had been obtained in the 1990s (2-6). In the research of the coupled fluid-structure vibration of overhead conductor, the force acting on the vibration objects were considered to be equivalent to the force that fluid with the same yaw angle and relative velocity acted on the same fixed objects, and dynamics equations and the criterion to judge the stable region of the galloping of the conductor were obtained. In the analysis of wind induced vibration of the conductor, the unsteady aerodynamic characteristics were related to the flow separation and the generation of the vortex and have strong nonlinear characteristics, so it was difficult to use simple theory or some analytical formula to describe the unsteady aerodynamic characteristics due to various actual conductors and the diversity and complexity of the iced conductors. Most of the early results were obtained by the wind tunnel experiment and established empirical formulae of the aerodynamic parameters. In recent years, many scholars do a lot of research works in the field of disaster prevention of the transmission lines. The references (7-8) tested the static and dynamic aerodynamic characteristics of the galloping of iced bundled power lines. However, the wind tunnel test method, which is the important method to study the aerodynamic characteristics, can not meets the demand of diversity of the practical engineering due to their high cost, long testing cycle, measuring accuracy, limitations of methods, the equivalence problem of test models and practical problems. The development of the numerical wind tunnel technique based on computational fluid dynamics (CFD) provides a new way to calculate the fluid dynamics parameters of the conductor. The reference (9) analyzed the drag coefficients of the bundled conductor and found that the drag coefficients defined in the Chinese code might be over-estimated. The reference (10) studied the external flow field around transmission line