On the suitability of k– ε turbulence modeling for aerosol deposition in the mouth and throat: a comparison with experiment

Deposition of a polydisperse aerosol (MMD=4.8 μm, GSD=1.65) in a replica of a human mouth–throat is measured experimentally and compared to predicted results using computational fluid dynamics (CFD). The mouth–throat geometry represents an idealized, average mouth–throat. Experimental values of the fraction η of aerosol depositing in this mouth–throat are obtained using a radiolabelled, nebulized aerosol generated with a Pari LC+ nebulizer. Gamma scintigraphy is used to measure amounts of aerosol depositing at laminar (2 l min −1) and turbulent (28.3 l min −1) flow rates. Deposition is predicted computationally using a commercial CFD code (TASCflow) for these two flow rates. For the turbulent case, the standard k– ε turbulence model was used with the most common eddy lifetime model for turbulent particle dispersion [Gosman and Ioannides (1983) J. Energy 7, 482–490]. Good agreement between experiment and simulation is found for laminar flow (experiment: η=15.7±0.3%, simulation η=16%), but not for turbulent flow (experiment: η=25.6±0.7%, simulation η=65%). Measured and predicted pressure drops agree well for laminar flow (experiment: 0.26±0.02 Pa, simulation: 0.25 Pa), but differ less dramatically for the turbulent case than does deposition (experiment: 25.2±0.5 Pa, simulation: 22.3 Pa), indicating that accurate prediction of particle deposition in this geometry requires more accurate prediction of the fluid dynamics than can be obtained with the present turbulence model