There are controversial requirements involved in developing numerical methodologies in order to compute the flow in industrial fans. The full resolution of turbulence spectrum in such high-Reynolds number flow configurations entails unreasonably expensive computational costs. The authors applied the study to a large unidirectional axial flow fan unit for tunnel ventilation to operate in the forward direction under ambient conditions. This delivered cooling air to the tunnel under routine operation, or hot gases at 400°C under emergency conditions in the event of a tunnel fire. The simulations were carried out using the open source code OpenFOAM, within which they implemented a very large eddy simulation (VLES) based on one-equation SGS model to solve a transport equation for the modelled (subgrid) turbulent kinetic energy. This subgrid turbulence model improvement is a remedial strategy in VLES of high-Reynolds number industrial flows which are able to tackle the turbulence spectrum’s well-known insufficient resolution. The VLES of the industrial fan permits detecting the unsteady topology of the rotor flow. This paper explores the evolution of secondary flow phenomena and speculates on its influence on the actual load capability when operating at peak-pressure condition. Predicted noise emissions, in terms of sound pressure level spectra, are also compared with experimental results and found to agree within the uncertainty of the measurements. 1. Introduction The selection of the state-of-the-art industrial fan technologies for tunnel ventilation normally fulfills user demands that require high volume flow rates and total pressure rises. As such, the specified operating area falls in several cases within the range ordinarily characterizing mixed flow fans. In addition to these performance requirements, two additional factors contribute to the complexity of design processes of the fan range customized for emergency and routine operating modes [1, 2]. First, the fan must have installation in either a vertical or horizontal layout and, second, the fan range must be able to accommodate the effect of unsteady pressure pulses which the trains generated in ventilation shafts [3–6]. These requirements imply levels of complexity in the design process and diversity in the operations that are significantly beyond the historic norm within the fan industry. Therefore, the application of standard methodologies is inappropriate and significant changes are taking place in the design process of large industrial fans. Although the conventional approach to fan design has
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