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VIRTUAL PERIMETER IN TUNNELS: A NEW METHOD FOR DETERMINING AVERAGE AIR VELOCITY

Omar Lanchava

Abstract

This paper proposes the concept of the virtual perimeter as an innovative approach for determining the average velocity of ventilation flow in tunnels. Average velocity is a fundamental parameter that defines volumetric and mass flow rates, energy losses, and thermal regimes. Classical methods, based on multipoint measurements with anemometers, are difficult to apply in large tunnels and, in many cases, practically impossible. The virtual perimeter identifies the zone of the tunnel’s cross-section where the local velocity is closest to the average. Based on numerical modeling, three virtual perimeters are distinguished: for calibration; for periodic verification; for operational monitoring. This approach makes it possible to obtain the numerical value of average velocity directly by placing a sensor/anemometer at a single point. The obtained results, with an accuracy of ±3–10%, fully meet engineering requirements. The method simplifies the measurement process, reduces costs, increases safety for operators, and creates a standardized, repeatable tool. Its application enables easier control of energy losses and thermal regimes. The paper presents colored schemes and tables that provide engineers with an immediate map for practical work. It is noteworthy that the introduction of the virtual perimeter for determining average ventilation flow velocity in tunnels represents a new, energy-efficient, and safe method that can be integrated into international standards.

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