Numerical modelling of droplet formation in mesh nebulizers

Numerical modelling of droplet formation in mesh nebulizers

Chemmalasseri, E.A.

Boersma, B.J. (mentor)

Mechanical, Maritime and Materials Engineering

Process and Energy

Fluid Dynamics

2012-09-14

It is common practice to use the inhalation route to deliver medicine in the form of aerosol to treat patients with pulmonary ailments like cystic fibrosis. In pulmonary drug delivery, medicine in the form of small droplets is inhaled by patients and delivered to their lungs. A major challenge faced in developing such devices is that effective drug delivery is only obtained for a narrow droplet size distribution. Large droplets (> 10 micron) remain stuck in the throat of the patient, and small droplets (< 1 micron) are immediately exhaled out. Conventional nebulizers are generally inefficient in this aspect. For this purpose, portable micro system devices called vibrating mesh (VM) nebulizers are being developed at Philips Research Europe, that use ultrasonic waves produced by a piezoelectric crystal to generate an aerosol of droplets by passing the liquid through a mesh of micro-sized nozzles. The goal of the project was to maximize the droplet throughput (> 1 gram/minute) with minimal treatment time, at specific droplet size (between 4 and 5 micron, for 95% of all droplets) for maximum treatment efficacy. A time-resolved finite element simulation model is constructed to model the process of droplet formation. It includes the multi-phase flow of liquid and air, both inside and outside the channel. The model was developed using the commercial code COMSOL. In COMSOL, the level set method can be used along with Navier-stokes equations to model and advect the interface between two fluids. Furthermore, a scheme to carry out parallel computation of multiple parameters was devised. This was accomplished using the distributed computing facility at Philips Research Europe. Using the data from simulations, several aspects of flow dynamics were studied. Different modes of operation of the device were identified. Also, an effective method to visualize the simulation data was developed.

two-phase flow
level set method
mesh nebulizer
finite element method

http://resolver.tudelft.nl/uuid:16a442ae-05ea-4b35-817f-3239131b0bac

2013-09-14

Student theses

master thesis

(c) 2012 Chemmalasseri, E. A.