Computational Study of Turbulent Airflow in a Full-Scale Aircraft Cabin Mockup: Part 1 — Determination of Boundary Conditions at the Outlet of Air Diffusers

The first step in understanding different mechanisms associated with contagious disease transmission in airliner cabins is adequately resolving the airflow field. A Computational Fluid Dynamic (CFD) approach is used to study the behavior of turbulent airflow and calculate the velocity data in a full-scale, 11-row, Boeing 767 aircraft cabin mockup. The calculated velocity data will be used later as the initial condition in tracer gas and particle dispersion simulations. Reynolds-Averaged Navier Stokes (RANS) method is employed for the airflow simulations. Based on the outcomes of our previous investigation in which the accuracy of different k-ε models were evaluated, the RNG k-ε model is used for turbulence modeling. The geometry of the cabin as well as the taken approach for mesh generation is also explained along with the adopted numerical method for solving the governing Navier-Stokes equations. Three different sizes of grids are examined for grid uncertainly analysis. The main challenge in airflow simulations is the determination of the unknown boundary condition (velocity magnitude and direction) at the outlet of the cabin air diffusers (or inlet of the aircraft cabin). To overcome this challenge, the mean velocity data measured by omni-probes located very close to the diffuser outlets are used as the first trial boundary conditions at the inlet of the cabin. Then, based on the differences between experimentally measured and steady RANS estimated velocity data at the omni-probes positions, the airflow velocity at the inlet of the cabin is modified and this procedure is repeated until the differences between the measured and calculated velocity data at omni-probe positions become negligible.