Numerical Simulation And Wind Tunnel Tests Of Aerodynamic Forces Of Iced Conductors

Under a certain wind speed, an iced conductor with non-circular cross-section isprone to gallop, which is also called galloping. The aerodynamic parameters andchanging rate of those of iced conductors are the key factors of a galloping. In theprevious study of galloping, the aerodynamic parameters of the iced conductors aremainly investigated in the steady flow.Furthermore, few relevant research on turbulenceflow and skew wind cases are found so far.By the wind tunnel tests and numericalsimulation, the aerodynamic characteristics and instability criterion of galloping ofcrescent iced conductors are investigated and discussed in the skew wind flow andturbulence flow.The contents and conclusions are as following.â‘ A study on aerodynamic characteristics of an iced conductor. Aerodynamiccharacteristics tests of crescent iced conductors in the wind were carried out in the windtunnel. From which aerodynamic parameters of4-bundle conductors and singleconductor with three different ice thicknesses are obtained.Using FLUENT, numericalmodels of iced conductor are built to calculate. Life coefficients drag coefficients andmoment coefficients of three different thicknesses of crescent iced conductors and toanalyze the effects of ice thicknesses on the aerodynamic characteristics. The instabilityof crescent iced conductor was predicted by conditions of the negative aerodynamicdamping. Results show that the simulated results fit well with those of the wind tunneltests. The aerodynamic coefficients increase with the increasing ice thicknesses larger;the instable regime of Den Hartog criterion is wider than that of Nigolcriterion.Galloping is easier to occur on conductors of larger ice thicknesses in certainrange.â‘¡A study on aerodynamic characteristics of iced conductor under skew winds.Aerodynamic characteristics tests of crescent iced conductors under skew winds arecarried out in the wind tunnel.By FLUENT, three-dimensional numerical models of icedconductor are built to compute. The drag coefficients, lift coefficients and momentcoefficients of iced conductor in yawed angel range of-500~00and00~-500. Resultsshow that drag coefficients decrease gradually with the yaw angle, which the curve oflift coefficients fluctuate from positive to negative with the yaw angle,whose spike isclose to20o; the moment coefficients vary with yaw angle as periodic shape,and isrelative small. According to Den Hartog criterion, the model of single iced conductor under skew winds is easier galloping. According to Nigol criterion, the model of singleiced conductor under skew wind flow is easier to gallop than under normal wind flow.Itis better to take the wind tunnel test for measuring the wind loads of iced conductorsunder skew wind flow than conventional decomposition method based on the normalwind speed.â‘¢A study on aerodynamic characteristics in turbulence flow. The aerodynamiccharacteristics tests of crescent iced conductors were carried out in the wind tunnel.Bythe FLUENT, numerical models of iced conductor are built to analyze the influence ofturbulence on aerodynamic characteristics and stable regime of galloping. The resultsshow that amplitudes of drag coefficients increased with increasing turbulence intensityas well as the peak of lift coefficients. The results show that of the iced4-bundleconductors with crescent shape in turbulence flow are easier to gallop.The unstableregime of galloping hardly depend on turbulence intensity.However,galloping willeasily occur at high turbulence intensity.