Analytical Model for Pressure Maintenance of Vacuum Tube Structures

초록

A vacuum tube structure is an essential part of emerging innovative transportation systems such as the super-speed tube train or pneumatic freight conveying systems. One of the basic technical requirements of a vacuum tube structure for realization of these systems is maintaining the reduced pressure inside the tube for a certain period of time. In this study an analytical model for description of the pressure change inside the tube structures is presented. Two different cases are considered for developing the analytical model depending on what kind of fluid is intruding through the vacuum tube. One is an air-intrusion model, which reproduces the case where the tube structure is installed on the surface, and the other is a water-intrusion model for submerged vacuum tubes. Formulas for determining the flow rate of the fluid (either air or water) movement caused by the pressure difference inside and outside the tube structure are derived on the basis of Darcy’s law. The derivation is performed for the cases with both compressible and incompressible fluid.