Numerical Analysis of Freight Wagon Rolling Dynamics on a Classification Hump

This paper presents an engineering-oriented numerical model for predicting the longitudinal rolling dynamics of a freight wagon on the first profile section of a railway classification hump, from the crest to the first retarder position. The study focuses on resistance mechanisms that govern speed buildup and, consequently, the intensity of impacts, vibration excitation, and noise during yard operations. Rolling resistance at the wheel–rail interface and losses in axle-box bearings are represented by equivalent tangential forces, which makes it possible to account for rolling with partial wheel slip in a physically consistent way. Aerodynamic drag is incorporated through the relative air speed, and headwind/tailwind scenarios are included in the force balance. The governing relations are formulated using the momentum theorem and solved numerically for practical parameter sets corresponding to typical hump grades and wagon properties. A baseline case study and a sensitivity analysis quantify how mass, grade, rolling resistance level, drag coefficient, and wind speed alter the velocity–distance and velocity–time histories. The results show that wind and resistance uncertainties can materially shift the approach speed at braking and coupling locations, which motivates adaptive retarder settings and yard-specific resistance calibration. The proposed framework provides transparent links between measurable inputs (track geometry, wagon mass, and ambient wind) and safety-relevant outputs (peak speed and impact energy), and it is suitable for extension toward vibration/impact models of couplers, retarders, and running gear. In contrast to existing approaches, the proposed model combines aerodynamic drag, rolling resistance, and longitudinal wagon dynamics within a unified framework, enabling a more realistic interpretation of impact intensity and vibration excitation during classification hump operations.