Abstract
In this study, the aerodynamic characteristics of the three-dimensional evacuated tube transportation (ETT) system based on the Reynolds-averaged Navier−Stokes κ−ω shear-stress transport turbulent model were investigated. The effects of two key parameters on the drag and flow topology of the ETT system, namely the travelling speed and ambient pressure in the tube, were studied. Compared with trains in the atmospheric environment without the tube (i.e., the open system), the ETT system shows considerable drag reduction with suitable operating parameters in the tube, particularly at a higher travelling speed range. The drag varying with the speed from subsonic to supersonic, shows various change trends at different speeds because of their distinct flow structures. The higher pressure in front of train head was observed to be reduced by choking, and a low pressure in the wake by expansion waves led to rapid increase in the drag and drag coefficient. The relationship between the drag and operating pressure was observed to be approximately linear for both the subsonic and supersonic speeds.