The DPM theory

In DPM, the trajectories of particles, droplets or bubbles are computed in a Lagrangian frame. The particles can exchange heat, mass, and momentum with the continuous gas phase. Each trajectory represents a group of particles, all with the same initial conditions. The DPM simulation models the air as the continuous phase and the cough or sneeze droplets as the discrete phase. The air comes in through windows on one side of the building as defined, and leaves through the windows on the opposite wall. The cough or sneeze source was from an index patient, with location in the ward as defined. Findings from this work can as well apply to all public gatherings and public places such as the shared offices, public transports, restaurants, classrooms, places of worship, market places, shopping malls or supermarkets. To compute the DPM concentration in ANSYS Fluent, it is calculated by defining the DPM concentration as given in Eq. (1);

where, the strength of particle is defined as (Eq. 2a,b):

In Eq. (2a), dt_flow is change in flow. Therefore, from Eq. (1) and Eq. (2b), it follows that:

The DPM concentration maps (x-y plots) were therefore considered convenient as easy to interpret, and was used together with the DPM concentration contours to present the particle transport behaviors in the indoor environment.