The influence of natural draught on the air flow in a tunnel with longitudinal ventilation

This article presents the results of full-scale in situ measurements of airflow, conducted in a real-world road tunnel. The tunnel is located in Gdansk city under one of the limbs of the Wisla river. The total length of the tunnel is 1378 m and the middle section of the tunnel is located at the deepest level. The inclination of the road is 3% and 4% for both directions from the deepest point. The tests covered measurements of airflow at 56 separate measuring points. The natural draught was determined, in addition to airflow rates for varying configurations of jet fan operation. The results were compared to those which were taken from automatic tolls mounted in the tunnel. The article also contains a theoretical discussion concerning a method for determining the natural draught in a tunnel.