Particles dispersion due to human prostration cycle and ventilation system in a prayer room

Abstract

The aim of this study is to investigate the human wake flow field generated by prostration cycle during prayers and its impact on resuspended particles' dispersion. Prostration constituted of forward and backward rotations at 0.9 rad/s of the upper body towards and away from the floor respectively. The cycle was simulated by computational fluid dynamic (CFD) model that was coupled to a dynamic mesh to adapt to the moving manikin at a time step of 0.0005 s. The flow field was validated experimentally using a moving thermal manikin in a climatic chamber. The validated CFD model was used to track the dispersion of floor-resuspended particles using the Lagrangian technique at particle sizes of 1 μm and 10 μm.It was shown the human prostration cycle disturbed the flow field in the person's microenvironment. The forward and backward rotations resulted in significant pressure gradients and a wake flow trailing behind the human body with peak velocities and turbulence intensities reaching 1 m/s and 20% respectively. During the backward rotation away from the floor, the flow was moving vertically upwards and was pushed out and pulled back into the wake. This behavior was the cause of the transport and dispersion of particles from the floor to higher levels in the space. Concentration fields showed that the breathable air quality was highly compromised near the floor. Moreover, 1 μm particles presented a higher contamination risk than 10 μm since they were transported more easily by the wake flow to the person's breathing zone.