Aerodynamic parameters of across-wind self-limiting vibration for square sections after lock-in in smooth flow

• Main Authors: Wu, Jong-Cheng; Chang, Feng-Jung, Wu, Jong-Cheng
• Other Authors: 淡江大學土木工程學系
• Language: English
• Published: London: Elsevier Ltd 2011
• Subjects: Arctic
• Online Access: http://tkuir.lib.tku.edu.tw:8080/dspace/handle/987654321/89033; http://tkuir.lib.tku.edu.tw:8080/dspace/bitstream/987654321/89033/4/index.html; http://tkuir.lib.tku.edu.tw:8080/dspace/bitstream/987654321/89033/-1/Aerodynamic parameters of across-wind self-limiting vibration for square sections after lock-in in smooth flow.pdf

The paper aims to identify the across-wind aerodynamic parameters of two-dimensional square section structures after the lock-in stage from the response measurements of wind tunnel tests under smooth wind flow conditions. Firstly, a conceivable self-limiting model was selected from the existent literature and the revisit of the analytical solution shows that the aerodynamic parameters (linear and nonlinear aerodynamic dampings Y1 and ε, and aerodynamic stiffness Y2) are not only functions of the section shape and reduced wind velocity but also dependent on both the mass ratio (mr) and structural damping ratio (ξ) independently, rather than on the Scruton number as a whole. Secondly, the growth-to-resonance (GTR) method was adopted for identifying the aerodynamic parameters of four different square section models (DN1, DN2, DN3 and DN4) by varying the density ranging from 226 to 409 kg/m3. To improve the accuracy of the results, numerical optimization of the curve-fitting for experimental and analytical response in time domain was performed to finalize the results. The experimental results of the across-wind self-limiting steady-state amplitudes after lock-in stage versus the reduced wind velocity show that, except the tail part of the DN1 case slightly decreases indicating a pure vortex-induced lock-in persists, the DN2, DN3 and DN4 cases have a trend of monotonically increasing with the reduced wind velocity, which shows an asymptotic combination with the galloping behavior. Due to such a combination effect, all three aerodynamic parameters decrease as the reduced wind velocity increases and asymptotically approaches to a constant at the high branch. In the DN1 case, the parameters Y1 and Y2 decrease as the reduced wind velocity increases while the parameter ε slightly reverses in the tail part. The 3-dimensional surface plot of the Y1, ε and Y2 curves further show that, excluding the DN1 case, the parameters in the DN2, DN3 and DN4 cases almost follow a symmetric concave-up distribution versus the density under the same reduced wind velocity. This indicates that the aerodynamic parameters in the DN3 case are the minima along the density distribution. 補正完畢 國外 SCI Y 紙本 GBR