Marika Pilou

Η αριθμητική μοντελοποίηση της μεταφοράς σωματιδίων που βρίσκονται διασκορπισμένα σε ρέοντα βιορευστά είναι ο βασικός σκοπός της παρούσας διατριβής. Συγκεκριμένα, διερευνώνται οι μηχανισμοί που διέπουν τις αλληλεπιδράσεις σωματιδίων – ρευστών χρησιμοποιώντας τεχνικές της δυναμικής ρευστών. Η συνεχής φάση (ρευστό) επιλύεται με χρήση υπάρχοντος κώδικα, ο οποίος βασίζεται σε μεθόδους της υπολογιστικής ρευστοδυναμικής (computational fluid dynamics – CFD). Ιδιαίτερη σημασία κατά την ανάπτυξη του μοντέλου δόθηκε στην επίλυση της μεταφοράς της σωματιδιακής φάσης με προσέγγιση Euler. Η χρήση της περιγραφής κατά Euler έχει ως αποτέλεσμα την άμεση αντιμετώπιση της διάχυσης των σωματιδίων και του υπολογισμού τη συγκέντρωσης τους. Ωστόσο, τα αδρανειακά φαινόμενα δεν ενσωματώνονται εύκολα στην κατά Euler μορφή της Εξίσωσης Μεταφοράς των Σωματιδίων (particle transport equation – PTE). Για να συμπεριληφθούν, επομένως, τα αδρανειακά φαινόμενα στην μεθοδολογία Euler, θα πρέπει να χρησιμοποιηθεί μια ...

Occupational exposure to manufactured nanomaterials (MNMs) and its potential health impacts are of scientific and practical interest, as previous epidemiological studies associate exposure to nanoparticles with health effects, including increased morbidity of the respiratory and the circulatory system. To estimate the occupational exposure and effective internal doses in a real production facility of TiO2 MNMs during hypothetical scenarios of accidental release. Commercial software for geometry and mesh generation, as well as fluid flow and particle dispersion calculation, were used to estimate occupational exposure to MNMs. The results were introduced to in-house software to calculate internal doses in the human respiratory tract by inhalation. Depending on the accidental scenario, different areas of the production facility were affected by the released MNMs, with a higher dose exposure among individuals closer to the particles source. Granted that the study of the accidental relea...

The paper presents an integrated methodology that combines experimental and modeling techniques and links exposure to airborne particulate matter (PM) with internal dose in the respiratory system and burden in adjacent tissues over a period of time. The methodology is used to estimate doses in the respiratory systems of elders that reside in 10 elderly care centers (ECCs) in the metropolitan area of Lisbon. Measurements of PM were performed in the ECCs and combined with a time-budget survey for the occupants. This information served as input to the first model that estimated particle doses in the different regions of the respiratory tract of the elderly, and then a second model was used to calculate particle build-up in the alveolar region, the interstitium and the hilar lymph nodes of the elders over a 5-year exposure period. It was found that in 5 years of continuous exposure to the average particle concentration measured over all ECCs, 258 mg of all particles are deposited on the...

The present work focuses on the study of particle deposition in the human lung under different breathing patterns. Transport and deposition of particles, with diameters from a few nanometers to several micrometers, is calculated using a well validated, 1-D, fully Eulerian, mechanistic numerical model that solves the particle general dynamic equation in the whole lung taking into account breathing dynamics. The examined breathing patterns include normal breathing and a variety of abnormal ones with tidal volumes and/or breathing frequencies outside the normal ranges. The numerical experiments indicate that breathing patterns do not alter significantly whole lung deposition fraction. They do, however, affect where the deposited particles are located within the lung, and the effect varies for different sized particles.

Exposure to airborne particulate matter (PM) is of utmost importance in the area of nanotechnology safety as it has been associated with increased hazard to human health. Exposure characterization of particle concentration by size though a key determinant of the ability of PM to induce adverse health effects, is not enough for assessment of its potential health impact; estimation of particle intake, translocation and clearance are equally important parameters. In the present study, a biomathematical, mechanistic model is used to calculate internal doses from PM exposure in an office environment. The model consists of two parts; the first is a lung transport and deposition model that deals with aerosol and breathing dynamics, whereas the second is a compartmental model that calculates particles clearance/retention. For the monitoring of the airborne exposure levels, a Grimm 1.108 spectrometer was used, measuring particles’ number concentration in a diameter range between 0.30μm and 2...

There are numerous applications that aerosols are used as drugs, where the delivery of the particulate matter in specific sites of the respiratory tract is crucial for their effectiveness. Aerosol flows in bifurcations, which can be considered as building blocks of the lungs, are therefore of great importance for biomedical applications. In the present study, in-house computational models are used for constructing the computational grid [Makris et al.,2011,Comp Meth in Biomech and Biomed Eng(In press)], calculating the fluid flow field [Neofytou & Tsangaris,2006,Int J for Numerical Meth in Fluid (51),p.489–510] and studying the transport and deposition of inertial particles [Pilou et al.,2011,Aerosol Sc & Tech(45),p.1376-1387] in a single physiologically realistic bifurcation under steady state inspiratory flow. The effects of fluid flow characteristics (Reynolds number, asymmetry in the branches) and particle size are investigated. The model results are compared with experimental f...

A numerical model for the simulation of aerosol flows via an Eulerian-Eulerian, one-way coupled, two-phase flow description is presented. An in-house computational fluid dynamics code, which utilizes the finite volume method and incorporates high order discretisation schemes, is used to obtain the velocity and pressure fields of the gaseous (continuous) phase. A modified convective diffusion equation, which includes inertial, gravitational and diffusive particle transport, is solved by the use of computational fluid dynamics techniques in steady state. The model is validated by comparing the calculated laminar fluid flow and particle deposition fractions with experimental studies of aerosol flows in a laminar-flow 90o bend of circular cross-section. Model predictions are also compared to numerical predictions of Eulerian-Lagrangian models. Particle concentration profiles at different cross-section are calculated and deposition sites on the wall boundary are indicated. For the range ...

ABSTRACT Estimation of internal dose from inhalation of toxic particulate material is of interest to toxicologists, health-care providers and regulators of air-quality standards. Conversely, there are numerous applications that aerosols are used as drugs, where the delivery of the particulate matter in specific sites of the respiratory tract is crucial for their effectiveness. Aerosol flows in bifurcations, which can be considered as building blocks of the lungs, are therefore of great importance for biomedical applications. In the present study, in-house computational models are used for constructing the computational grid, calculating the fluid flow field and studying the transport and deposition of particles in a single physiologically realistic bifurcation under steady state inspiratory flow. The effects of fluid flow characteristics (Reynolds number, asymmetry in the branches) and particle size are investigated. The model results are compared with experimental findings available in literature.

Abstract The objectives of modeling in this work were (a) the integration of two existing numerical models in order to connect external exposure to nanoparticles (NPs) with internal dose through inhalation, and (b) to use computational fluid-particle dynamics (CFPD) to analyze the behavior of NPs in the respiratory and the cardiovascular system. Regarding the first objective, a lung transport and deposition model was combined with a lung clearance/retention model to estimate NPs dose in the different regions of the human respiratory tract and some adjacent tissues. On the other hand, CFPD was used to estimate particle transport and deposition of particles in a physiologically based bifurcation created by the third and fourth lung generations (respiratory system), as well as to predict the fate of super-paramagnetic particles suspended in a liquid under the influence of an external magnetic field (cardiovascular system). All the above studies showed that, with proper refinement, the developed computational models and methodologies may serve as an alternative testing strategy, replacing transport/deposition experiments that are expensive both in time and resources and contribute to risk assessment.

ABSTRACT The investigation of aerosol flows in bifurcations is significant in biomedical applications, because this geometry resembles the branching airways of the lung. Most of the existing computational studies regarding aerosol flow in branching airways use Lagrangian description for the particulate phase, when particle inertial effects are taken into consideration. \textcolor{blue}{In the present study a fully Eulerian model is used for studying the transport and deposition of inertial particles under steady state inspiratory flow in the single physiologically realistic bifurcation created by generations G3-G4 of the human lung}. In-house codes are used to create the geometry and the computational grid, obtain the fluid flow field and calculate particle concentration. Deposition fractions are calculated, concentration profiles are shown and deposition sites are indicated under different flow conditions (Reynolds number and flow asymmetry in the branches) and particles of various sizes (1-10$\mu$m). It is found that total particle deposition fraction is loosely dependent on fluid flow Reynolds number and our results are in agreement with experimental findings. Moreover, total deposition fraction does not change significantly between symmetric $Q_1/Q_2=1$ and asymmetric $Q_1/Q_2=2$ flow conditions, but is considerably lower for the totally obstructed case, $Q_2=0$. On the contrary, deposition sites and particle concentration profiles depend on the various flow conditions. Apart from deposition at the bifurcation, which is present at all cases, deposition sites downstream the bifurcation move towards the outer bifurcation wall and daughter tube exit as Reynolds number increases. For the $Q_2=0$, it is also shown that particles are trapped and deposit even in the obstructed daughter tube. In all studied cases, it is found that there is a particle-free region at the outer wall, at the beginning of the daughter tubes opposite the bifurcation. The straightforward formulation of deposition modelling and derivation of detailed concentration profiles along the bifurcation are major advantages of the fully Eulerian methodology used in the study.