Numerical investigation on the aerodynamics of a tunnel ventilation fan during pressure pulses

The paper reports on the simulation of a ventilation fan under pressure pulses generated by train passages in tunnel and metro systems. Such pulses alter the volume flow rate through the fan, and consequently the overall aerodynamics, causing structural stress, vibrations, and forcing the unit to operate off-design. A proper understanding of the unsteady aerodynamics during the pressure fluctuations is mandatory to obtain useful guidelines to fan designers. Here the pressure waves due to train passage are modelled as a region of rapidly changing volume flow rate. The fan operation are computed with a large eddy simulation (LES) one-equation sub-grid scale (SGS) model implemented in the open source code OpenFOAM. This investigation provides an insight of the effects on the turbulent structures developing along the fan blades, as well as the conspicuous detrimental effect on the aerodynamics of the fan.