The Effect Of Reynolds Number And Skew Wind On Aerodynamic Characteristics And Instability Of A D-shape Iced Conductor

The iced transmission line experienced self-excited vibration with large amplitude, low frequency in specific circumstances, which resulted failure of conductors, flashover, even tower destroy, threatened the safety of power supply system.The quasi-steady self-excited vibration was used widely to explain the large amplitude galloping characteristics described by quasi-steady aerodynamic force, which obtained by using static aerodynamic force test techniques. The aerodynamic force on structure having shape like D cross-section is influenced by several parameters such as Reynolds number, wind direction and surface roughness. The studies on influence parameters on aerodynamic force characteristics are still not enough to prevent the iced transmission line galloping.The rigid section model pressure test was used to obtain the wind pressure on model with D shape cross-section. The variation of wind pressure distribution, aerodynamic force characteristics and galloping instabilities with Reynolds number and skew wind were analyzed.For aspect of wind pressure distribution, the time-history of wind pressure coefficients under five Reynolds numbers and four skew wind directions was obtained by wind tunnel test. The effects of Reynolds number and wind direction on mean and fluctuating wind pressure coefficients and circumferential correlation of wind pressure coefficients were analyzed.For aspect of aerodynamic force coefficients, the time-history of aerodynamic force coefficients under five Reynolds numbers and four skew wind directions were obtained by results of pressure coefficients integral, so the effects of Reynolds number and wind direction on mean and impulse force coefficients and span-wise correlation of aerodynamic force coefficients was analyzed. Otherwise applicability of oblique direction wind decomposition method on the D shape cross-section was investigated.For aspect of instability characteristic, A formula was deduced, we can fix the aerodynamic damping coefficients of the model in any Reynolds number and oblique wind direction. With this formula we obtain the aerodynamic damping coefficients of 5 Reynolds number and 4 oblique wind directions and then analyze the stability of different Reynolds number and oblique wind directions.