Drag reduction of high-speed trains via low-density gas injection

Aerodynamic drag reduction is crucial for the development of high-speed trains. This study considers the principle of supercavitation torpedo drag reduction and conducts wind tunnel tests and improved delayed detached eddy simulation numerical simulations to develop a drag reduction technique using low-density gas injection on the surface of a high-speed train. Models for jetting gases with different densities on the surface of the high-speed train were employed, and the aerodynamic drag, frictional resistance, pressure resistance, and flow field structure were compared and analyzed. The results demonstrated that jetting of low-density gas reduced the drag of the train, whereas air and high-density gas increased the drag. The jetting gas reduced the frictional resistance of the train to a certain extent and low-density gas injection significantly reduced the frictional resistance. However, the pressure resistance coefficient increased with an increase in the density of the jetting gas, resulting in increased drag. The density of the gas medium in the boundary layer significantly decreased when low-density gas was jetted and the effect of reducing the friction resistance was superior. The pressure resistance between the front and rear of the jet port increased with an increase in the gas density, thereby increasing the drag on the train.