Aerodynamics and Sensor Arrays in Tunnel Ventilation Monitoring
Tunnel Ventilation Monitoring is a critical safety infrastructure designed to manage air quality and maintain thermal equilibrium within enclosed subterranean passages. The primary objective is the regulation of Carbon Monoxide ($CO$), Nitrogen Dioxide ($NO_2$), and particulate matter levels generated by internal combustion engines, while also providing "Smoke Control" in the event of a thermal incident.
The monitoring system relies on a distributed network of anemometers and gas sensors. Ultrasonic sensors measure flow velocity and direction by calculating the "Time-of-Flight" of acoustic pulses between transducers. This data allows the central SCADA (Supervisory Control and Data Acquisition) system to adjust the pitch and speed of jet fans. In a fire scenario, the system enters "Critical Velocity" mode, ensuring that the airflow is sufficient to prevent "backlayering"—a dangerous phenomenon where smoke flows against the ventilation direction, trapping commuters.