Modularized fluid-mechanics-based model design and validation for intermodal freight train air brake systems

High-fidelity fluid-mechanics-based brake system simulations, which have broad capability, are essential for improving and understanding brake systems and managing safety of long intermodal freight trains. Traditional modeling approach lacks the flexibility required for intermodal trains that are usually composed of wagons of different brake systems and are frequently remarshalled to match origin–destination flows and terminal constraints. This article develops a modularized framework that builds a complete train model from reusable and selectable components connected by pressure–mass-flow ports. Validation against measured data for two distributor valve types in different train lengths, rated pressures and brake-pipe reductions shows good reproduction of brake system behavior. Intermodal train case studies, coupled with longitudinal train dynamics, indicate that valve types and settings only weakly change brake-wave speed but can reduce build-up non-uniformity, while wagon length and mass make-ups dominate in-train forces: placing longer wagons toward the rear delays rear-end braking and, with non-uniform masses, inertia mismatch amplifies differences in peak buff/draft forces. The results highlight the value of modular modeling for rapid reconfiguration and team-based development.