Aerodynamic characteristics of a tube train

Recently, full-scale research about a passenger tube train system is being progressed as a next-generation transportation system in Korea in light of global green technology. The Korea Railroad Research Institute (KRRI) has commenced official research on the construction of a tube train system. In this paper, we studied various parameters of the tube train system such as the internal tube pressure, blockage ratio, and operating speed through computational analysis with a symmetric and elongated vehicle. This study was about the aerodynamic characteristics of a tube train that operated under standard atmospheric pressure (open field system, viz., ground) and in various internal tube environments (varying internal tube pressure, blockage ratio, and operating speed) with the same shape and operating speed. Under these conditions, the internal tube pressure was calculated when the energy efficiency had the same value as that of the open field train depending on various combinations of the operating speed and blockage ratio (the P–D relation). In addition, the dependence of the relation between the internal tube pressure and the blockage ratio (the P–β relation) was shown. Besides, the dependence of the relation between the total drag and the operating speed depending on various combinations of the blockage ratio and internal tube pressure (the D–V relation) was shown. Also, we compared the total (aerodynamic) drag of a train in the open field with the total drag of a train inside a tube. Then, we calculated the limit speed of the tube train, i.e., the maximum speed, for various internal tube pressures (the V–P relation) and the critical speed that leads to shock waves under various blockage ratios, which is related to the efficiency of the tube train (the critical V–β relation). Those results provide guidelines for the initial design and construction of a tube train system.