Influence mechanism of cable terminal on airflow and leeward pollution distribution of high-speed train roof post insulator

The airflow around the high-speed train roof insulator modifies the distribution of fan-shaped, non-uniform contamination on the umbrella skirts, and the flashover voltage decreases as surface contamination becomes more uneven. Wind tunnel tests at 55 m/s show that the presence of a cable terminal significantly alters the leeward pollution distribution compared with a single post insulator. To investigate the underlying mechanism, an Euler–Euler two-phase flow model including both the cable terminal and the insulator was developed. Simulations reveal that airflow upwash and downwash on the leeward side of the insulator modify spanwise and streamwise flow patterns and the passage width between umbrella skirts, thereby shifting the boundaries of heavily polluted zones. Pollution accumulation experiments of 3 D-printed scale models confirmed the predictive capability of this approach. These results clarify how nearby structures influence airflow–pollution interactions and provide guidance for evaluating leeward pollution characteristics, optimizing insulator layouts, and understanding flashover behavior under non-uniform contamination conditions.