Theoretical calculation and numerical simulation of different static airtightness of trains

• Derives cabin pressure calculation models for positive and negative pressure conditions based on one-dimensional isentropic flow theory. • Proposes a flow coefficient calibration method for high-precision and efficient calibration across varying leakage properties. • Establishes functional relationships between flow coefficient and leakage path area for circular and square cross-sections under positive/negative pressure. • Validates the theoretical model with high R² values (0.9928–0.9936) against experimental data, enabling accurate evaluation of train body airtightness.