## 3 Case Study: Peng-Cheng Cooling Tower
### Wind Tunnel Model Tests Using an Aero-Elastic Model of Peng-Cheng Tower  
In the TJ-3 ABL wind tunnel with the dimensions of 15 m wide, 2 m high and 14 m long at Tongji University, aero-elastic model tests were carried out. Based on the Chinese standard GB/T 50102-2003 [26], the Type B ABL flow field was simulated using spires and roughness elements. Flow characteristics simulated in the TJ-3 wind tunnel are presented in Figure 8 and compared with the simulation targets (the empirical formulae obtained by generalizing large quantities of field measurement data) [27; 28; 29] and the flow characteristics measured on site in the Peng-cheng electric power station on 29 November 2011. As shown in Figure 8, the wind tunnel test data are close to the empirical formulae, but they are different from the full-scale measurement results for all wind characteristics. In Figure 8a, the non-dimensional power-spectral density simulated in the wind tunnel at around 1 m height, where the simulated turbulence integral scale is around 0.3 m, agrees very well with the von Karman spectrum; however, the field measurement result obtained at around 130 m height is much greater than the empirical formula and the wind tunnel test data in the low frequency range. In Figure 8b, the turbulence intensity measured in the wind tunnel is close to the empirical profile below a certain height, and it is a bit greater than the empirical result above that height; however, the empirical formula and the wind tunnel test result are both noticeably greater than the field measurement data over the full height. A similar situation holds true for the mean wind velocity profiles presented in Figure 8c. As can be seen, the wind tunnel mean wind velocity profile and the empirical curve agree very well with each other; however, they are smaller than the data measured at the engineering site of the Peng-cheng electric power station over the full height. The above observations suggest that the empirical ABL flow field can be accurately simulated in the wind tunnel using the conventional spire-roughness passive simulation method; however, the flow field simulated in the wind tunnel could still be noticeably different from the flow field at the realistic engineering site. This could probably lead to distorted wind loads measured on scaled physical models in the wind tunnel (flow characteristic effects). Figure 7: Comparison between the pressure differences and the dynamic pressures for different cases. According to the method described in Ref. [19], a 1:200-scaled beam-net aero-elastic model is manufactured for the Peng-cheng cooling tower (Figure 9). The main steps of manufacturing the beam-net aero-elastic model are presented in Appendix A of this article, which were also reported earlier in Ref. [19]. According to our experiences, the most difficult step in the process of manufacturing the model is determining the initial values of the uncertain parameters \(X_{1}\) to \(X_{6}\) (see Appendix A for their definitions) for use. The method adopted by the present study for determining the initial values of these uncertain parameters for the aero-elastic model of the Peng-cheng cooling tower are presented below for reference. To obtain the initial values of the uncertain parameters \(X_{1}\) to \(X_{6}\), a representative local drum section of the Peng-cheng tower at the height of around 130 m is simulated using detailed shell elements first, and its 1 st-5 th order dynamic characteristics are calculated accordingly (see Figure 10,c,e,g,i). Second, a corresponding preliminary beam-net model is established using a beam element with uncertain parameters \(W_{ver,i}\), \(D_{cit,j}\) and \(W_{cit,j}\) (see Appendix A for their definitions).