Abstract
This paper presents a numerical study of the deposition of spherical charged nano-particles caused by convection, Brownian diffusion and electrostatics in a pipe with a cartilaginous ring structure. The model describes the deposition of charged particles in the different generations of the tracheobronchial tree of the human lung. The upper airways are characterized by a certain wall structure called cartilaginous rings which modify the particle deposition when compared to an airway with a smooth wall. The problem is defined by solving Naver-Stokes equations in combination with a convective-diffusion equation and Gauss law for electrostatics. Three non- dimensional parameters describe the problem, the Peclet number Pe = 2ūa/D , the Reynolds number Re = ūa/v and an electrostatic parameter α=α2c0q2/(4e0κT) . Here U is the mean velocity, a the pipe radius and D the diffusion coefficient due to Brownian motion given by D=κTCu/3πμd , where Cu is the Cunningham-factor Cu=1+λ/d(2.34+1.05exp(-0.39d/λ)) Here d is the particle diameter and λ the mean free path of the air molecules. Results are provided for generations G4-G16 of the human airways. The electrostatic parameter is varied to model different concentrations and charge numbers.
Highlights
Use of Carbon-nanotubes in material design enables the development of new materials with superior properties
We note that the deposition is lower for a tube with a cartilaginous ring structure, which can be explained by the lower concentration of particles and the lower values of the electric field in the separated flow regions
The model includes convective and Brownian diffusion transport as well as effects from the electric field created by the charged particles
Summary
Use of Carbon-nanotubes in material design enables the development of new materials with superior properties. A drawback of this development is that these particles when inhaled may be toxic and can cause substantial health risks of the human lung [1] In experiments these particles are known to be electrically charged which probably leads to an increase in particle deposition in the lung. For low space-charge densities the dominant transport mechanism is the electric field that occurs from the image charge caused by the interaction of a particle and a grounded wall. This case has been studied by [4,5,6]. We consider the additional effects of the cartilaginous ring wall structure
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