Assessing the obstacle effect on jet fan flow variability in car parks using computational fluid dynamics

Abstract

The presence of obstacles may compromise the efficiency of the ventilation systems of underground car parks. One such case occurs when jet fans are close to beams or air ducts placed on the ceiling of the park. In this situation, understanding the extent and conditions at which the flow is disturb is of fundamental importance. To start addressing this question, in this study, Computational Fluid Dynamics (CFD) results were combined with Principal Component Analysis. The geometry under study was reduced to a simplified underground car park envelope, an impulse jet fan and a downstream obstacle placed on the ceiling of the park. As a first step, 34 computational fluid dynamics simulations of the isothermal incompressible turbulent flow were performed, randomly varying the distance of the obstacle to the fan and the jet fan discharge angle according to different distributions. Afterwards, representative results were selected and rewrote in the principal components space, with the aim of understanding the impact of the obstacle on the flow through identification and interpretation of the underlying factors. Because of the three-dimensionality and complexity of the flow, it is hard to select the output variables that are representative and can quantify the jet flow disturbance due to the obstacle. In this work, a first attempt was made, and the flow conditions (distance of fan to obstacle and jet fan angle) typified in accordance with these variables.