Vehicle back constant jet drag reduction is one of the current research hotspots. This study explores the effect and principle of constant jet drag reduction in the back of a vehicle by combining theoretical analysis, wind tunnel test, and numerical simulation with the Ahmed-like vehicle body model as the research object. The results show that the optimal jet position is at a certain distance in front of the transition line between the vehicle’s slant back and straight back, the optimal jet velocity is near 0.5 times the vehicle speed, and the optimal jet angle is slightly upstream in the direction of the normal of the plane where the jet hole is located. In this study, the optimal jet position is position 4, the optimal jet velocity is 20 m/s, and the optimal jet angle is 120° (pointing upstream) from the slanting back. Under the above conditions, the constant jet at the back of the vehicle can reduce the aerodynamic drag by 7.5%. The principle of drag reduction by constant jet includes reducing the intensity of the vehicle wake vortex and changing the position of the vehicle wake vortex. The effects of pressure and wake flow field (velocity, vortex volume, turbulent kinetic energy) are shown, the optimal jet parameters are determined, and the principle of drag reduction by constant jet at the back of the vehicle is analyzed.
