The Minimum Highway Horizontal Radius Considering the Bernoulli Effect on Running Vehicles

The effects of winds are not considered when traditionally determining the minimum highway horizontal radius. Some literature has discussed the direct forces of crosswinds, but the indirect lateral aerodynamic force induced by the Bernoulli effect has been overlooked so far. In this paper, the Bernoulli effect on running vehicles was investigated using the CFD (computational fluid dynamics) method. The velocity of front wind wasn’t uniformly distributed in the lateral direction, a series of simulations of a bus were conducted in FLUENT, and the lateral aerodynamic forces induced by the Bernoulli effect were calculated. The numerical study shows that when the gradient of wind speed variation goes over 5 m/s per meter, the ratio of the lateral force to the gravity of the bus will exceed 2%. Finally it is suggested that all the limiting values of the highway horizontal radii should be increased for safety reasons. This optimization study may provide a useful reference to the forgiving road design in special areas exposed to asymmetric wind conditions, such as high-class roads along deep gorges.