## 2 Configurations of Wind Tunnel Setup  
### Wind Tunnels and Models  
Two wind tunnels belonging to Central South University were utilized in these two experiment as shown in Figure 1a,b. The width and height of the test sections of these two wind tunnels are 450 mm \(\times\) 450 mm and 3000 mm \(\times\) 3000 mm, respectively. For clear representation, the smaller wind tunnel is named as WT-I, whereas the larger one is named as WT-II. Without any turbulence generators, the flow in the WT-I and WT-II with turbulence intensities smaller than 0.6% could be considered as uniform based on the current specification [11]. Please see [34] for more detailed geometric parameters of the above two wind tunnels.  
Two groups of wind tunnel test models were made to match the WT-I and WT-II, which are simplified from a practical engineering model in China as shown in Figure 1. On one hand, as depicted in Figure 1a, the first group models scaled by 1:200 were used for smoke-wire visualization in WT-I. The widths, heights, and lengths of the train and bridge-deck models are \(b\times d\times l\) = 16.3 mm \(\times\) 18.5 mm \(\times\) 450.0 mm and \(B\times D\times L\) = 98.0 mm \(\times\) 14.0 mm \(\times\) 450.0 mm, respectively, resulting in a maximum blockage ratio of 6.2%. In this flow visualization experiment, the models were made by 3D printing technique. The wind angle of attack \(a\) was set in [\(-\)12\({}^{\circ}\), 12\({}^{\circ}\)] with an interval of 2\({}^{\circ}\). The incoming flow velocity is \(U_{\infty}\) = 2 m/s, and the corresponding Reynolds number (\(Re\)) based on \(U_{\infty}\) and \(d\) is of 2.5 \(\times\) 10\({}^{3}\). On the other hand, the second group of models scaled by 1:40 were used for pressure field and flow profile measurements as shown in Figure 1b in WT-II. The widths, heights, and lengths of the train and bridge-deck models are \(b\times d\times l\) = 81.6 mm \(\times\) 92.3 mm \(\times\) 2000.0 mm and \(B\times D\times L\) = 490.0 mm \(\times\) 70.0 mm \(\times\) 2000.0 mm, respectively, resulting in a maximum blockage ratio of 4.6%. For brevity, only the geometrics of this group of models are depicted in Figure 2. In the pressure field and profile measurement experiment, the train model was still made by 3D printing technique, whereas the bridge-deck model was made of wood with an aluminum spine embedded inside. The test range of \(a\) was also set in [\(-\)12\({}^{\circ}\), 12\({}^{\circ}\)] with an interval of 2\({}^{\circ}\), while the incoming flow velocity is \(U_{\infty}\) = 20 m/s corresponding to \(Re\) = 1.25 \(\times\) 10\({}^{5}\) (based on \(U_{\infty}\) and \(d\)). Please note that, only the train's shoulders are rounded without any sharp corners, thus all the Reynolds numbers in this paper are calculated based on \(d\).  
Figure 1: Mode installations: (**a**) Models for flow visualization, and (**b**) Models for pressure field and flow profile measurements.  
Figure 2: Model geometric parameters: (**a**) pressure test points in the lateral direction; (**b**) pressure test sections in the longitudinal direction; and (**c**) flow profile test points. (Unit: mm).  
As described in Figure 2, \(x^{t}\)-\(y^{t}\) and \(x^{b}\)-\(y^{b}\) denote the geometric coordinate systems of the train and bridge-deck models, respectively. The coordinate origins are fixed at the centroids of the cross sections of the test models.