Wind tunnel test on aerodynamic coefficients of multi-bundled conductors under skew winds

Abstract A series of wind tunnel tests were conducted to study the aerodynamic coefficients of multi-bundled conductors under skew winds. Inclined model conductors were designed to simulate various wind incidence angles. Several coefficients and factors were defined for analyzing the effect of the Reynolds number, the angle of attack, the shielding effect, and the wind incidence angle on the aerodynamic coefficients. The test results were validated using available data for a wind incidence angle of 90°. It was found that the drag coefficient-Reynolds number curve of the conductors differed considerably from that of a circular cylinder. A value of 1.0 is recommended for the drag coefficient of a single conductor. The aerodynamic coefficients were strongly dependent on the angle of attack, and a change in the angle of attack resulted in the aerodynamic coefficients varying by more than 10%. Furthermore, it was observed that the shielding effect can lead to the overestimation of the wind load by up to 25%. A value of 0.95 is recommended for the shielding effect coefficient. The independence principle can be reliably used for practical design, even though it causes the normal wind load to be slightly overestimated. Axial wind loads for wind incidence angles of 75° and 45° were remarkably high. It is recommended that for these angles, they be considered to be 0.3 and 0.55 times the normal wind load, respectively. Finally, a simple method for calculating the normal and axial force coefficients under skew winds is proposed.