investigating the effect of train speed and ground clearance on aerodynamics of a simplified high-speed train

The present paper investigated the effect of train speed and ground clearance on aerodynamic forces on a simplified high-speed train. for this purpose, 20 different cases, including trains with five different speeds and four varied ground clearances were numerically simulated. the results showed that increasing the train speed has a dual effect on increasing the vertical upward lift forces. non-dimensional ground clearances above than 0.22 at speeds above 250 km/h, results in the upward lift forces dramatically and leaded to instability of the train. at ground clearances below than 0.092, increasing the speed increased the downward force, enhancing the stability of the train. moreover, further analyzing the ground clearance effect demonstrated that in ground clearance value of about 0.048 lift force has an approximately constant value at different train speeds. the air velocity profiles under the train revealed a dimensionless rise with increasing ground clearance except at the front of the train. this increase was precisely apparent at speeds of 350 km / h and resulted in a 29% increase in some sections below the train. this rise in speed can disrupt the balance of passengers and pedestrians, and workers around the train.