Determining Critical Wind Velocity During Fire Accident in Alborz Tunnel

Smoke and toxic gases created by fire accidents in tunnel are very harmful for tunnel users health and safety .So fresh air supply for fire smoke control in the fire upstream, is important .Thus, the critical velocity is a most important factor for this .In order to determine the critical velocity during fire in the Alborz tunnel 3dimensional model of the tunnel and fire was created by FDS software .Fire with 100 mw size for 960second in model with 500m length was simulated. Fire and Smoke was modeled by HRR and heptanes’ combustions. Unsteady flow and combustions was simulated by LES and Eddy break up model. Model was meshed by 50 cm cell. Finally, simulation result was validated by experimental equation .simulation predicted value for critical velocity is 3.5 m/s which have good agreement with Oka and Atkinson experimental equation so we propose 3.5 m/s as critical velocity for fire with 100 mw in Alborz Tunnel .