# Evaluation of the Aerodynamic Effect of a Smooth Rounded
## 2 Methodology: Wind Tunnel Experimental Tests
### Experimental Setup  
Wind tunnel tests were performed in the GVPM (Galleria del Vento Politecnico di Milano) wind tunnel of Politecnico di Milano. This facility corresponds to a closed-circuitwind tunnel with two test sections placed in a vertical arrangement. For this test campaign, the high-speed (characterised by a very low turbulence intensity) test section of the wind tunnel facility was used. The main characteristics of the high-speed test section of wind tunnel are summarised in Table 1.  
The scaled model was mounted over a splitter plate specifically developed to control the boundary layer thickness. In Figure 1a a picture of the splitter plate mounted in the test section is displayed; while in Figure 1b, the vertical profile of the mean wind speed measured over the splitter plate and the target value required by the EN14067-6 are plotted. The instrumentation used during the test to measure forces and moments is a six-components dynamometric balance, a strain-gauge based balance (RUAG Aerospace model 19). The scaled model was instrumented also with pressure sensors. Pressure measurements were performed using the Intitium high-speed scanning pressure equipment and the ESP miniature pressure scanners. The small size of the scanners allows them to be positioned inside the model near the measurement points, thus reducing the length of the tubes. The scaled model of the train consists of:  
1. First car: instrumented with an internal six-component dynamometric balance for measuring forces and moments, and 160 pressure taps placed around the surface of the vehicle;
2. Dummy car: placed downstream to reproduce the correct boundary conditions; it corresponds to half of the second vehicle, in compliance with the requirement prescribed by the EN 14067-6 standard. All the dimensions of the original vehicle were reduced following the 1:15 scale ratio, in order to obtain geometric similarity with the real train. The 1:15 scale ensures the minimum Reynolds number required by the European Standard (2.5 \(\times\) 10\({}^{5}\)) at both wind speeds is reached. Mechanical contact between instrumented model (first vehicle) and dummy car is always avoided. The distance between the two vehicles was reproduced with the correct \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Test Section** & **Dimensions** & **Max Wind Speed** & **Turbulence Intensity** \\  & **[m]** & **[m/s]** & **[\%]** \\ \hline GVPM High-speed & 4 \(\times\) 3.84 \(\times\) 6 & 55 & \textless{}0.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Wind tunnel test section characteristics. Figure 1: Splitter plate of GVPM wind tunnel: (**a**) Splitter plate mounted on the test section; (**b**) vertical profile of the mean wind speed measured over the splitter plate. separation that is present on the real train. The geometry of bogies was simplified in agreement with the EN 14067-6 standard. Infrastructure scenario corresponds to the standard Single Track Ballast and Rails, STBR (EN-14067-6). The wind tunnel scaled model of the ETR1000 train is displayed in Figure 2, on the left: the CAD model of the scaled train and infrastructure scenario is illustrated; on the right: the actual scaled model mounted on the high-speed test section of the wind tunnel is displayed. The dynamometric balance is mounted inside the scaled model, fixed to the car body and to the balance support. This support is rigidly connected to the rotating table of the wind tunnel using two vertical bars placed in correspondence of the bogies as shown in Figure 3.  
Moreover, to also measure the pressure around the surface of the first car, 160 pressure taps were disposed on the train surface. Eleven rings of pressure taps were set along the train in the positions indicated in Figure 4.  
Tests were carried out at two different wind speeds, 30 m/s and 55 m/s.