Mode localization phenomena and stability of disordered trains and train-like articulated systems travelling in confined fluid

The possible existence of mode localization in a chain of flexibly interconnected cylinders, representing a high-speed train travelling in a tunnel is investigated, in the presence of some disorder in the chain. Specifically, imperfections in the mass and springs in the model are considered as possible sources of mode localization, and it is shown that in general they can do so. This is part of a broader study into the dynamics of high-speed trains running in a tunnel, or more generally of a train-like system travelling in a coaxial cylindrical tube and subjected to aerodynamic forces associated with lateral motions of the cylinders. Each cylinder in the model is coupled to the other cylinders and is supported by springs, such that it has both translational and rotational degrees of freedom. Two models are used: a lumped-parameter Euler–Bernoulli beam model (LEB) and a lumped-parameter Timoshenko-beam model (LTB). The results of this study show that Timoshenko beam effects of rotational inertia and shear deformation have a considerable influence on the mode localization phenomena and that imperfections in the supporting springs have a considerable influence on the stability of the LTB model.