A Study on the Aerodynamic Drag of Transonic Vehicle in Evacuated Tube Using Computational Fluid Dynamics

The characteristics of aerodynamic drag for Transonic Vehicle in Evacuated Tube was investigated using computational fluid dynamics. At first, parametric study on the system was performed according to the Mach number of the vehicle’s speed (Machv), evacuated pressure of the tube (Pret), and blockage ratio (BR) between the vehicle and tube via axisymmetric flow analysis; the Machv ranged from 0.3 to 1.0. The Pret was 100, 1,000 and 10,000 Pa and the BR was 0.1, 0.2, and 0.4. In the calculations, the aerodynamic drag of the vehicle was larger when the BR and the pressure became larger. Concerning the Machv, the drag coefficient (Cd) became the maximum when the Machv was near the Kantrowitz limit and decreased, which showed the typical transonic flow pattern. Then, three dimensional flow analysis was performed by changing the Machv from 0.3 to 1.0 and setting the BR and the Pret as 0.34 and 100 Pa, respectively by referring the Hyperloop Alpha documentation. From the calculations, the Cd from three dimensional flow simulations were somewhat larger than those of axisymmetric ones because of the eccentricity of the vehicle inside the tube. However, the pattern of Cd according to the Machv was compatible with that of axisymmetric ones.