Keywords: train, crosswind, tornado, aerodynamic force, Rankin model.

In this paper, the aerodynamic forces acting on a train passing through a tornado were estimated using a simple model. The effects of the size of the tornado and the path of the train on the aerodynamic forces were investigated using the model. In the model, the flow field near the ground was represented by using a Rankin vortex model. The aerodynamic forces were estimated by assuming the forces acting on each section of the train is proportional to the square of the wind speed. The results were as follows: in the case of the train crossing the vortex centre, the side and lift forces become the maximum at the instant the car runs at points where the tangential velocity is the maximum. The yawing moment becomes the maximum at the vortex centre. Assuming that the maximum tangential velocity is constant irrespective of the vortex size, as the core radius of vortex increases, the side and lift forces increase and gradually reach a constant value. When the core radius of vortex is 0.3875 times of the car length, the yawing moment becomes the maximum, and then it decreases to zero. In the case that the path of the train is offset from the vortex centre, the aerodynamic forces rapidly decrease as the offset distance increases.

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