1. H. BIOLLAY, E. CASALE SCETAUROUTE Tunneling and underground works division – Annecy, France J. OUAZZANI ARCOFLUID, Aix en Provence, France J.C. HANON Annecy City Road Division – Annecy, France CFD simulations of a fire in the underground parking of Annecy City Hall International PHOENICS Users Conference - Moscow 23-27 sept. 2002

2. SUMMARY 1 - INTRODUCTION 2 - PROBLEM PRESENTATION 3 - THE CFD MODEL 4 - THE RESULTS 5 - CONCLUSION International PHOENICS Users Conference - Moscow 23-27 sept. 2002

3. INTRODUCTION The problem relates to the Underground car park of the town Hall of Annecy (France). The car park shapes is a helical slab which revolves around a central atrium A fire start at the bottom of the car park Phoenics is used to simulate the heat and smoke evolution

4. PROBLEM PRESENTATION Front view Slope Exit Atrium 17 m Level -6 Level -5 Level -2 Level -6 Level -5 Natural ventilation ducts 34 m Mechanical ventilation ducts Staircases Top view Six level car park located in front of the town hall of Annecy The car park is underground (the entrance is located at ground 0)

5. The CFD Model Phoenics has been used to simulate such fire unsteady, 3D, cylindrical polar coordinatesunsteady, 3D, cylindrical polar coordinates VR geometry in cylindrical coordinatesVR geometry in cylindrical coordinates Turbulence model (k- RNG model)Turbulence model (k- RNG model) buoyancy phenomena generated by the firebuoyancy phenomena generated by the fire Immersol used to simulate radiationImmersol used to simulate radiation heat and smoke release - evolution in timeheat and smoke release - evolution in time stairwells, system of ventilation, ventilation shaft, stationed vehicles, atrium, wall separating the car park have to be definedstairwells, system of ventilation, ventilation shaft, stationed vehicles, atrium, wall separating the car park have to be defined

6. Mesh definition

7. Source terms and boundary conditions Fire represented by a source term of average 5 MW linear increase of 10 s - constant maximum power of heat (5 MW) during 20 mn Fire source takes into account a density of thermal emission of 1MW/m 3

8. External walls at a fixed temperature (15°C) Fans are placed at the top of the ventilation duct (Flow rate extraction of 8.8 m 3 /s with a turbulence intensity of 5%) Outside atmosphere is simulated wind of 2m/s at 15°C

12. CONCLUSION Use of Phoenics code to improve fire protection in the Annecy town hall car park appears to be a good choice Most heat is evacuated through the Atrium This movement leads to premature invasion of smoke at higher level but strongly slow downs the smoke along the helical slab which make it possible to use the stair-wells with slight architectural modifications as evacucation gates