# Effect of High-Speed Train-Induced Wind on Trackside UAV Thrust Near Railway Bridge
## 2 Experimental Setup  
The Wolsan bridge, which is located 8.6 km away from Singyeongju Station on the Gyeongbu high-speed railway, was used as the site of the experiment. The Wolsan bridge is constructed as a PSC box girder bridge and crosses a reservoir with four piers installed at 40 m intervals. The total length of the bridge is 200 m. Above the bridge, a continuous reinforced concrete track, that integrates both sleepers and concrete beds, is installed in both ascending and descending directions. On the tracks, contact wires that supply power to trains are placed in the longitudinal direction.  
An experimental setup was installed on the top of the bridge, as shown in Figure 1. Power was supplied to four 3-axis ultrasonic anemometers (R. M. Young Co., Traverse City, MI, USA) through a DC power supply and power distribution system. Furthermore, train-induced wind data, measured by the anemometers, was transmitted to a PC via an RS-232 hub. The UAV motor (T-Motor Co., Nanchang, China) and propeller were controlled through the control board, which was connected to a personal computer to acquire thrust data. The main specifications of the train-induced wind and UAV thrust measurement systems used in the experiment are listed in Table 1.  
Figure 1: Schematics of the train-induced wind and unmanned aerial vehicle (UAV) thrust measurement systems installed on top of the Wolsan bridge.  
As shown in Figure 2, a jig was mounted on the catenary mast, and four 3-axis ultrasonic anemometers were installed on the jig. The anemometers were installed at distances of 0.8, 1.3, 2.3, and 2.8 m from the train surface. Additionally, the anemometers were installed at the height of 2 m to measure train-induced wind velocity at the middle height of the train. For the measurement directions, the train travel direction was defined as the \(V\) axis, the train width direction as the \(U\) axis, and the height direction as the \(W\) axis.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**System** & **Component** & **Parameter** & **Value** \\ \hline \multirow{4}{*}{Train-induced wind measurement system} & \multirow{4}{*}{3-axis ultrasonic anemometer} & Wind velocity & 0-40 m/s \\  & & Resolution & 0.01 m/s \\  & & Accuracy & \(\pm\)1\% \\  & & Wind direction & 0-360\({}^{\circ}\) \\  & & Output speed & 32 Hz \\ \hline \multirow{4}{*}{UAV thrust test system} & Motor & Size & \(\Phi\)55.6 \(\times\) 33.9 mm \\  & & Configuration & 24N2 SP \\  & & Max. Power & 1000 W \\  & Propeller & Length/Pitch & 17 \(\times\) 5.8 inch \\  & & Weight & 32.5 g \\  & & Material & Carbon epoxy \\  & & Optimal RPM & 4000–6000 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Detailed specifications of the main components of the train-induced wind and UAV thrust measurement systems.  
Figure 2: Installation locations of the 3-axis ultrasonic anemometers and UAV thrust measurement system. (**a**) Distances between the 3-axis ultrasonic anemometers and the train. (**b**) Installed train-induced wind and UAV thrust measurement systems.  
The UAV thrust test stand was installed at a point 1.8 m away from the train surface, and the thrust measurement system was installed above it. To prevent the effect of train-induced wind on the measurement system during the experiment, the system was placed in an instrument box and installed on the inspection passage between the low height wall to prevent access to the train and the bridge railing.