Natural ventilation analysis in an underground construction: CFD simulation and experimental validation

•Natural ventilation in underground constructions using CFD.•CFD validation approach with ground temperatures.•3D scanner and temperature sensors to estimate boundary conditions.•Passive behaviour of the building components.•The access tunnel is the key element in the ventilation. This work evaluates the thermal and natural ventilation behaviour in an underground construction and explains the passive behavior of the building components (tunnel, chimney and cave) in different periods of the year. The CFD models developed take into account the temperature gradients of the terrain, which allows a more realistic simulation of the natural ventilation in underground constructions. The role of the building components in the regulation of the indoor environment vary dramatically in each period. Results show that thermal stability with zero energy consumption is reached in the cave despite the extreme outdoor temperatures. Further, the access tunnel is the key element in the ventilation of the underground construction, where the ground temperature plays an essential role in regulating natural ventilation. By contrast, the ventilation chimney plays a less important role due to lower air velocities. The approach and adjustments of CFD models presented here could be useful as a reference for other underground projects as a decision-making in the design of optimized ventilation and energy management systems.