3/17/2023 0 Comments Wake the dragon strainIn this study, six CTMs including a 3D scanned CTM and five simplified CTMs generated from various simplification approaches were employed to analyse the impact of CTM simplification on the prediction of airflow field and contaminant transport. While simplified computational thermal manikins (CTMs) are widely employed in CFD modes of occupied indoor spaces in order to save the computational cost, a criterion of simplification is still absent and the effects of CTM simplification are yet not clear. The spatial and temporal characteristics of the particle dispersion and concentration showed that higher walking speed was conducive to reducing human's exposure to contaminants in breathing region. The residual flow disturbances after the manikin stopped moving continued to induce the particle to spread and deposit over time. The airflow momentum induced by the moving body disturbed PM2.5 particles that were initially at rest on the floor to lift and become re-suspended due to its interaction with the trailing wake. The significant airflow patterns included: an upward-directed flow in front of the body combined with a high velocity downward-directed flow at the rear of the body a stagnant region behind the gap between the legs and counter-rotating vortices in the wake region. A series of numerical simulations of three walking speeds were performed to compare the flow disturbance induced by the walking motion. Particle transport from the floors and its re-dispersion was tracked by a Lagrangian approach. The manikin motion was achieved by a dynamic layering mesh method to update new grids with each time step. The impact of human-induced wake flow and particle re-dispersion from floors in an indoor environment was investigated by performing computational fluid dynamics simulations with dynamic mesh of a moving manikin model in a confined room. For duet running, we reveal the optimum duet-running formation where a following runner behind a pacemaker experiences small air resistances or strong drafts. For solo running, we reveal an increase in air resistance of more than 10% in comparison with the conventional result with no moving-belt system. Following, using this the developed moving-belt system, we investigate the air resistance on a runner in solo running and in duet running. As a result, we have confirmed the effective improvement of the velocity distributions in terms of flow uniformity and turbulence reduction, especially near the moving-belt surface. In the present study, we develop a moving-belt system, and show its basic performance, such as the distributions of time-mean flow velocity and turbulent intensity above the moving-belt using a hot-wire anemometer. Wind-tunnel experiments are the most effective approaches both to elucidate the flows around runners in track-and-field athletics, and to evaluate their air resistances.
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