Validating CFD predictions of nasal spray deposition: Inclusion of cloud motion effects for two spray pump designs

Momentum transfer from nasal spray droplets to the surrounding gas may create droplet cloud motion and influence nasal deposition patterns. The objective of this study was to develop a validated computational fluid dynamics (CFD) model of nasal spray deposition for two different spray-pump designs that includes cloud motion effects (i.e. two-way coupling) in a computationally efficient manner. Spray droplet transport and deposition were simulated in an average adult nasal airway model (that captures average drug delivery) using both two-way coupled and one-way coupled Euler-Lagrange frameworks. CFD model accuracy was established by comparing predictions of the two-way and one-way modeling frameworks with in vitro measurements. The two-way coupled simulation showed that momentum from the spray cloud resulted in displacement of surrounding gas, leading to an upward air velocity in the direction of the spray, which significantly increased the travel distance of smaller droplets with diameters equal to a median diameter of similar to 70 mu m and below. For the Flonase Sensimist spray pump, two-way coupling produced in vitro data, versus 47% relative error using one-way coupling. For the Flonase spray pump, two-way coupling did not improve posterior deposition agreement with both methods having a relative error of similar to 30%; however, two-way coupling showed substantial increase in posterior deposition. As a result, two-way coupling is likely needed for the simulation of most nasal spray pumps and additional factors may be important to better capture final formulation distribution of the Flonase product, like post-deposition liquid motion. Copyright (c) 2021 American Association for Aerosol Research