Nonlinear loss of runway friction under water contamination with altitude from SPH-FEM simulations and field tests

The mechanism underlying the deterioration of the aircraft tire–runway friction coefficient under conditions of water accumulation and runway contamination at high-altitude airports remains unclear. Existing research has primarily focused on low-altitude, normal-pressure environments, making it difficult to explain how changes in the tire–water film–runway contact state under low-pressure conditions affect friction performance. Based on field tests and smoothed particle hydrodynamics-finite element method fluid–structure interaction numerical simulations, this paper establishes a friction coefficient analysis model for water-contaminated runways in high-altitude, low-pressure environments, extending the simulation altitude range of 0–5000 m. The model's predicted friction coefficients showed 96.42% agreement with field test results, validating the model's reliability for evaluating macroscopic friction performance. The results show that as altitude increases, the corrected tire pressure rises from 1.2500 to 1.2973 MPa, while the runway friction coefficient decreases from 0.382 to 0.238, representing a total decrease of approximately 37.7%. The friction coefficient’s deterioration exhibits a distinct inflection point near 2438 m: below this altitude, it decays slowly in a nearly linear manner; above it, the deterioration transitions to a nonlinear, accelerated decline. This transition primarily stems from the coupled changes in tire contact deformation, effective contact area, and dynamic water separation effects at the interface under low-pressure conditions. Based on the above results, this paper establishes an empirical model of the friction coefficient for water-contaminated runways, with elevation as the core variable, providing a quantitative basis for evaluating runway friction performance and making operational safety decisions at high-altitude airports.