Experimental and numerical study of spray characteristics of nasal spray device
Creators: name: Fung, Man
Publisher: name: RMIT University
Year: 2024

description: This thesis has provided 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 range of spray that exits from the device, while the internal characteristics such as the droplet size distribution help to determine the probability 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 of another unsteady spray experiment using an in-house experimental test station to simulate the hand operations by patients have showed that there are three main phases of spray development (pre-stable, stable, and post-stable) that can be correlated by examining the spray width. A comparison with a human nasal cavity is made to put into perspective the dimensions and geometry that the spray atomization produces. The spray droplet size was analysed under different back pressures to mimic the drug delivery by adult and paediatric patients. It was found that the spray droplet size from the device operated by adult has smaller averaged Sauter mean diameter (SMD) which implies better drug absorption in nasal cavity. Also, the spray cone has less variation during stable stage. By prolonging the duration of this stage can improve the drug delivery performance and stability. The outcome has extended the current existing set of data to contribute toward a better understanding in nasal spray drug delivery. The numerical part of this thesis has presented the fine-tuned spray model constants of the linear instability sheet atomization model (LISA) and evaluated its performance for low pressure application. Some parameters that were evaluated include the dispersion angle and the liquid sheet constant that influences the droplet size distribution and dispersion. The simulation results were evaluated against experimental data that has been previously performed. It was found that the LISA model provided good comparisons when a dispersion angle of 3◦ and a liquid sheet constant of 1 were used. In addition, three scenarios were investigated: (i) influence of fluid droplet coupling; (ii) increase in mass flow rate; and (iii) changing the orientation from downward spray to upward spray.<br>