Large-Eddy Simulation of the aerodynamic and aero-acoustic performance of an industrial fan designed for tunnel ventilation

The development of industrial fans traditionally relies upon the use of empirical correlations and experimental analyses to validate both aerodynamic and acoustic aspects of fan performance. This paper presents the development of a computational based method focused on the prediction of unsteady aerodynamics and modeling of aero-acoustic sources. The authors applied the study to a single fan from a new range of large tunnel ventilation-axial flow fans. The fan specification required mechanical and aerodynamic properties that would enable it to operate in the forward direction under ambient conditions to provide cooling air to the tunnel under routine operation, and in the reverse direction at 400 degrees C under emergency conditions in the event of a tunnel fire. The final aerodynamic and mechanical design was additionally required to generate no more than 80 db during reverse operation, to ensure members of the emergency service could still communicate in the event of a fire. The simulations were carried out using the open source code Open-Foam, within which the authors implemented a (Very) Large Eddy Simulation (V)LES based on an one-equation sub-grid scale SGS model to solve a transport equation for the modeled (sub-grid) turbulent kinetic energy. This improvement of the sub-grid turbulence model is here considered as a remedial strategy in VLES of high-Reynolds industrial flows able to tackle the otherwise insufficient resolution of turbulent spectrum. The VLES of the industrial fan permits to detect the flow features such as three-dimensional separation and secondary flows. Predicted noise emissions, in terms of sound pressure level spectra, are compared with experimental results, and found to agree within the uncertainty of the measurements.