Effect of curvature radius and angle on aerodynamic characteristics of a sphere travelling in a branched tube system

Abstract

Compressible flow through a branched duct and the motion of a sphere through a high blockage ratio pipe are two important and engaging topics throughout the years. The results of studies on these topics are of practical relevance to many fields such as the gas pipeline technology, air transport systems in gas turbines technology, and tube transportation, etc. However, studies on the motion of a sphere in a branched duct are scarce. Studies of the motion of a sphere in a near-vacuum tube could contribute to the development of a branched Hyperloop system in the future. In this study, we investigated the effect of the tube curvature radius and angle on the aerodynamic characteristics of a sphere during its motion in a branched tube. We examined, quantified, and compared the variation of the drag, side force, and pressure waves for the cases where a sphere enters a branch considering six curvature radii (from 500 to 3000 m), three angles (10°, 15°, and 20°), three speeds (100, 200, and 300 m s-1), and two initial pressures (1/1000 and 1 atm) in simulations. The results indicated that the drag and side force vary only in the intersection region (region where the straight tube and branched tube intersect); before and after the intersection region, they are similar. With an increase in the curvature radius, the rate of drag reduction ($F_D$/max($F_D$)) decreases, while the changes in the angle do not affect variation of drag and side forces. Furthermore, we compared the motion of a sphere in straight and branched directions and found out that the flow in front and behind the sphere was similar for both directions.

KEYWORDS:

• Hyperloop system
• branched tube
• aerodynamic force
• sphere
• shock wave

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was supported by the MSIT (Ministry of Science and ICT), Korea, under theITRC (Information Technology Research Center) support program (IITP-2023-2020-0-01655) supervised by the IITP (Institute for Information & Communications Technology Planning & Evaluation). This research was also supported by the "Core Technology Development of Subsonic Capsule Train" of the Korea Railroad Research Institute (PK2301A1). This research was supported by the Chung-Ang University Graduate Research Scholarship in 2022.