External and Near-Nozzle Spray Characteristics of a Continuous Spray Atomized from a Nasal Spray Device

Computational fluid dynamics (CFD) simulations of nasal drug delivery often neglect the initial spray particle conditions (e. g., particle velocity) and instead introduce particles entrained by the inhaled airflow into the nasal cavity. The results presented in this study aim to provide some insight into spray droplet formation after atomization of a drug formulation from a nasal spray device. A commercial nasal spray device was tested under a constant flow in order to better understand its spray formation and characteristics. External characteristics such as the spray cone angle define the shape of the atomized spray that exits from the device, while the internal characteristics such as the droplet size distribution help to determine the likelihood of inertial impaction within the nasal cavity. The experimental method makes use of particle image velocimetry (PIV) and particle/droplet image analysis (PDIA) to obtain droplet diameters and spray velocities in different spray regions. Image processing techniques were applied to enhance visualization and a droplet concentration field. It was shown that there is some variation in the droplet diameters with respect to its radial and axial position from the spray orifice. Empirical curve fits for the particle size distribution were formulated to allow easier adoption of the data into CFD models. The dimensions of the external spray were shown to be much larger in comparison with the dimensions of a nasal cavity, which means that only a narrow portion of the spray will fit within the narrow cross sections of the nasal cavity. The results may be used for the validation of spray atomization models and applied to the particle deposition study of sprayed particles in nasal cavity in future.