Experimental and numerical modelling of nasal spray atomisation

Spray atomization is a common process found in different industries, where sprays under high injection pressure are widely recorded in the literature. Nonetheless, research on spray breakup mechanism under low pressure in pharmaceutical industry is still relatively rare. Numerical model in the Lagrangian approach was modified for simulating the spray formation from a nasal spray device in the current study. The Linear Instability Sheet Atomization (LISA) was applied to model the formation of spray droplets of a continuous spray from a pressure swirl atomizer. The secondary breakup of spray droplets was simulated by the Taylor Analogy Breakup (TAB) model. Two way momentum coupling was applied to handle the interaction between the gas and liquid phases. The droplet size distribution from numerical solution agreed with experimental result in literature. The external spray characteristics was also studied for comparison. Experimental work of unsteady spray was also performed to study the spray atomization from a nasal spray device. High speed camera and Particle/Droplet Image Analysis (PDIA) were used to determine the spray external characteristics. The atomization stages were defined into pre-stable, stable and post-stable stages, based on the spray cone width. The spray intensity and spray cone dimension were used to evaluate the drug delivery efficiency in different stages. The experimental data is a stepping stone for the validation of a numerical model for unsteady application. NOMENCLATURE Symbols a1, a2, a3 drag coefficient constants applied to smooth spherical droplets over several ranges of droplet Reynolds number d, D droplet diameter d0 volume median diameter D30 volume mean diameter D32 Sauter mean diameter ⃑ Additional acceleration term g gravitational acceleration h liquid sheet thickness k turbulent kinetic energy kw atomization wave number, defined as ̇ mass flow rate M mass Mp momentum exchange between droplets and air Oh Ohnesorge number, defined as √