A virtual mass model in train aerodynamics

Abstract

The paper presents a new approach to the research into the aerodynamic characteristics of vehicles and their interpretation. The approach is based on the theory of collision. The virtual mass is related to the unit coefficient of restitution of a central collision and to the absorption of kinetic energy. The basic system is chosen to be a train, and the system involving the virtual mass effect is air. A series of successive collisions of these two systems provides a model of air resistance. The expression derived for the unit virtual mass states that it is equal to a half of the coefficient of the square polynomial term of the air drag function. Thus, a physical interpretation of the virtual mass has been obtained and the metric system of the air resistance has been determined. A relation between the virtual mass and the most important aerodynamic characteristic, i.e. the coefficient of aerodynamic profile, has been established. © 2012 WIT Press.