Computational Study of the Effects of Particle Size, Particle Injection Configuration, and Operating Pressure Gradient on Turbulent Dispersion of Spherical Micron-Sized Particles in a Generic Mockup Aircraft Cabin

Abstract

Computational study of dispersion of particles is one way to evaluate the spread of contaminants and viruses amongst occupants of an enclosure, such as an aircraft cabin. In this investigation, the turbulent dispersion of particles in a ventilated generic cabin is studied. The generic cabin resembles one-half of a Boeing 767-300 aircraft cabin. In the first phase, the turbulent dispersion of particles injected through stainless steel straight vertical tube is simulated. A Lagrangian approach is used to predict the particle concentration in specified monitoring location inside the cabin. The steady RANS solutions for the airflow velocity data are used to initialize the particle-tracking calculations through the Discrete Phase Model (DPM). To calculate the effects of turbulence on the dispersion behavior of particles, a Discrete Random Walk (DRW) model is employed. The particle concentration field under steady-state, zero-gauge-pressure conditions for 3 μm and 10 μm spherical liquid particles are calculated. Through the comparisons between the measured and the calculated particle concentration data for the two examined sizes of mono-disperse particles, the effect of particle size on distribution behavior of micron-sized particles is investigated and discussed. In the second phase, in order to reduce the effect of initial injection velocity for 10 μm particles on their distribution, the straight injection tube is replaced by a cone diffuser while maintaining the upstream primary flow conditions. Using the same RANS model and under the new particle injection configuration, the characteristics of turbulent airflow in the cabin are found to be very similar to those of turbulent airflow without particle injection. A grid independency study is performed for the airflow velocity data prior to validation of the particle distribution results. The steady-state DPM simulations are performed initially for the zero-gauge-pressure condition and then the effect of pressurizing the cabin on particle distribution is investigated by increasing the gauge-pressure up to 0.025 inches of water. Through a detailed study, carried out to obtain an optimum number for the number of tries in the DRW, it is realized that the optimum number of tries is 175 for both cases of pressurized and non-pressurized cabin.