3. Running safety evaluation method for vehicle overturning caused by localized strong winds

It is known that localized strong winds, known as "building winds," can occur around high-rise buildings. However, safety assessment methods for trains running in the vicinity of such winds have not been established. Therefore, we proposed a running safety evaluation method for vehicle overturning caused by localized strong winds.

First, wind tunnel tests (Figure 1) and numerical fluid analysis (Figure 2) using a numerical wind tunnel developed by the Railway Technical Research Institute were conducted for building winds caused by two neighboring buildings.
As a result, we confirmed that the wind speed distribution (wind speed increase rate) of the wake generated by the two buildings can be accurately reproduced by analysis, and also clarified the magnitude and extent of the effect (Figure 3).
Next, we developed a vehicle behavior analysis method that takes into account the conditions under which the aerodynamic forces estimated from the wind speed distribution obtained in the analysis act on the running vehicle. The results show that the wheel load decreases as the vehicle enters the strong wind area outside the building from the wind shielded area that occurs downwind of the building (Figure 4).
As a result of a parameter study using this method, it was found that wheel load decreases more easily when exposed to sudden strong winds. In particular, when the vehicle is running at high speed and the rise time of the aerodynamic force acting on the vehicle is shorter than about 2 seconds, the decrease ratio of wheel load tends to increase.

This method can be used for evaluating running safety and considering effective countermeasures for crosswind (such as speed controls or the installation of windbreak fences) in areas where local strong winds are expected, such as around high-rise buildings, exits of tunnels, and ends of windbreak fences.