Analysis of wind attack angle increments in wind tunnel tests for the aerodynamic coefficients of iced hangers

Abstract

Wind attack angle increments are important inputs for the accurate and efficient wind tunnel test in analyzing the aerodynamic coefficients and Den Hartog galloping coefficients of iced cable structures. This research aims to investigate the interference of wind attack angle increments on the aerodynamic coefficients and Den Hartog galloping stability of iced hangers based on the aerodynamic coefficient theory and Den Hartog galloping theory, and by adopting the method of wind tunnel test. The analysis shows that considerable calculation error will be caused when directly using the conventional method during the processing and analysis of Den Hartog galloping for iced cable structures. The curve fitting of the aerodynamic coefficients of iced hangers in which their characteristics are better presented, for example, smooth-going characteristic, antisymmetric characteristics for lift coefficients, and symmetric characteristics for drag coefficients, can satisfy the accuracy requirement of the derivation of lift coefficients and can then be used to examine the Den Hartog galloping coefficients of iced hangers accurately. In cases where the wind attack angle increments are more than 3°, the wind attack angle that corresponds to the minimum value of the Den Hartog coefficients shows an offset. Meanwhile, distortions occur when determining the range of wind attack angles of Den Hartog galloping, and thus quantitative analysis cannot be conducted. These cases are only applicable to a preliminary study. The precision of the Den Hartog coefficients, which is solved in cases where the wind attack angle increments are not more than 3°, can meet the requirements for the Den Hartog galloping analysis. Results of this study can provide a reference for research on the galloping of iced hangers using the wind tunnel test.