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Inhalation of fibers has been a health concern for several decades. Although the use of some fibers, such as asbestos, was banned altogether in many countries, global demand for other fibers, such as man-made vitreous or carbon fibers, increases every year. The health hazard of fibers is given by their ability to penetrate deep into human lungs and avoid defensive mechanisms. This is mainly given by their anisometric shape and complex behavior in fluid flow, e.g. drag force acting on a fiber depends significantly on fiber orientation. The objective of the present work was to numerically investigate fiber transport and deposition in the model of child respiratory airways including the upper respiratory tract and tracheobronchial tree down to 2nd generation of branching. Computational fluid dynamics–discrete element method was employed to model a fiber motion during which the drag force was calculated based on actual fiber orientation in a flow. This method was compared to a simpler approach in which a modified drag coefficient accounting for fiber non-spherical shape was used. The results of the employed methods were compared.

Both pulmonary airway geometry and breathing pattern evolve from birth to adulthood. These gradual changes significantly influence airflow dynamics and subsequently particle transport and deposition. Regarding the airway structure, the differences between infants and adults are most profound till 5 years of age. Since that age the child airway geometry can be downsized from adult lungs. The objective of the present work was to investigate airflow patterns in child airways. The digital model of male respiratory airways was downsized to dimensionally correspond to a 5–year old child. Airflow simulations with properly validated RANS k–ω turbulence model were performed under steady inhalation boundary conditions. The inspiratory flow rate was 12.5 L/min. The velocity profiles just upstream of the first bifurcation were validated by Laser–Doppler anemometry (LDA) experiments. A replica of the same geometry as the one used in the simulation was 3D printed and part of the trachea was replaced by a glass tube. LDA measurements in several points upstream of the first bifurcation were carried out. The validated flow patterns were compared to the ones obtained in adult lungs.

Pari LC Sprint Star nebulizer is an inhaler device dedicated to delivering the liquid drug formulation into peripheral lung regions. The particle size is one of the critical parameters which determine the location of aerosol deposition within the human lungs. In this study, the particle size distribution of aerosol was measured by two different methods: Andersen Cascade Impactor (ACI) and Aerodynamic Particle Sizer (APS). Mass Median of Aerodynamic Distribution (MMAD), and Geometric Standard Deviation (GSD) were evaluated. MMAD gained by APS was approx. 7 µm, MMAD acquired by ACI was approx. 2.5 µm. According to the results, these two measuring methods are not very consistent, and the comparison of the particle size acquired by the different methods is not appropriate.

The ability to precisely predict the fate of inhaled fibres is important for toxicologists as well as for pharmaceutists struggling to utilize fibres as carriers of a medication. However, the complexity of fibre movement in human airways still represents a significant challenge for programmers of codes for simulation of fibre flow. This conference contribution introduces the theoretical equations of fibre motion which can be used for calculation of the fate of inhaled fibres, and also, in the second part, first results of high-speed camera recorded trajectories of fibres downstream of a realistic human airway bifurcation are presented as an illustration of the real behaviour of fibres in the lungs.

Inhalers are hand-held devices which are used for administration of therapeutic aerosols via inhalation. Nebulizers are larger devices serving for home and hospital care using inhaled medication. This contribution describes the basic principles of dispersion of aerosol particles used in various types of inhalers and nebulizers, and lists the basic physical mechanisms contributing to the deposition of inhaled particles in the human airways. The second part of this article presents experimental setup, methodology and preliminary results of particle size distributions produced by several selected inhalers and nebulizers.

The efficiency of drug delivery administered by inhalation depends, among other factors, such as size and shape of aerosol particles, significantly also on the flow in the airways. As many lung diseases change both the breathing pattern and the shape of airways, we focus in this study on the influence of several selected diseases on the distribution of flow between the lung lobes and on changes the diseases induce on the course of flowrate. First, we present results of a literature survey focused on the published records of pathological breathing patterns. In the second part, we describe the newly designed breathing simulator and the implementation of the patterns into it. The last part is focused on the experimental verification of fidelity of the simulated breathing patterns.

The presence of aerosol deposition hot-spots in human airways presumably contributes to development of various diseases. The overall aerosol deposition in human lungs can be predicted with sufficient accuracy nowadays. However, the prediction of localized aerosol deposition poses arduous challenge, namely in diseased lungs. Numerical simulation is considered to be a promising tool for the successful prediction. Yet, the validation of such simulations is difficult to perform, as not enough experimental data acquired using realistic airway replicas is available. This paper presents a first comparison of localized deposition measurement and simulation performed on the identical realistic geometry. The analysis indicates that both approaches yield similar results for low Reynolds number flows.

Electronic cigarettes (e-cigarettes) have become very popular recently because they are marketed as a healthier alternative to tobacco smoking and as a useful tool to smoking cessation. E-cigarettes use a heating element to create an aerosol from a solution usually consisting of propylene glycol, glycerol, and nicotine. Despite the wide spread of e-cigarettes, information about aerosol size distributions is rather sparse. This can be caused by the relative newness of e-cigarettes and by the difficulty of the measurements, in which one has to deal with high concentration aerosol containing volatile compounds. Therefore, we assembled an experimental setup for size measurements of e-cigarette aerosol in conjunction with a piston based machine in order to simulate a typical puff. A TSI scanning mobility particle sizer 3936 was employed to provide information about particle concentrations and sizes. An e-cigarette commercially available on the Czech Republic market was tested and the results were compared with a conventional tobacco cigarette. The particles emitted from the e-cigarette were smaller than those of the conventional cigarette having a CMD of 150 and 200 nm. However, the total concentration of particles from e-cigarette was higher.

Measurement of velocity in human lungs during breathing cycle is a challenging task for researchers, since the measuring location is accessible only with significant difficulties. A special measuring rig consisting of optically transparent replica of human lungs, breathing simulator, particle generator and Laser-Doppler anemometer was developed and used for investigation of the velocity in specific locations of lungs during simulated breathing cycle. Experiments were performed on two different replicas of human lungs in corresponding measuring points to facilitate the analysis of the influence of the geometry and its simplification on the flow. The analysis of velocity course and turbulence intensity revealed that special attention should be devoted to the modelling of vocal cords position during breathing, as the position of laryngeal jet created by vocal cords significantly influences velocity profiles in trachea. The shapes of velocity courses during expiration proved to be consistent for both replicas; however magnitudes of peak expiratory velocity differ between the corresponding measuring points in both the replicas.

It seems to be very convenient to receive a medicine by inhalation instead of injection. Unfortunately transport of particles and targeted delivery of a drug in human respiratory airways is very complicated task. Therefore we carried out experiments and tested different methods for evaluation of particle deposition in a model of human lungs. The model included respiratory airways from oral cavity to 7th generation of branching. Particles were dispersed by TSI Small-scale Powder Disperser 3433 and delivered to the model. The model was disassembled into segments after the deposition of the particles and local deposition was measured. Two methods were used to analyse the samples, fluorescence spectroscopy and optical microscopy. The first method was based on measuring the intensity of luminescence, which represented the particle deposition. The second method used the optical microscope with phase-contrast objective. A dispersion of isopropanol and particles was filtrated using a vacuum filtration unit, a filter was placed on glass slide and made transparent. The particles on the filter were counted manually and the deposition was calculated afterwards. The results of the methods were compared and both methods proved to be useful.

Prediction of the fate of inhaled fibres in human airways represents a significant challenge in comparison with spherical particles. There are several ways of computation ranging from a simplified approach assuming equivalent spheres with empirical corrections to sophisticated numerical solutions of momentum and rotations in three-dimensional flow. Each of these mathematical approaches has its area of application. However, their precision is still insufficient namely because of the lack of experimental data for validation. Especially data on the behaviour of fibres under transient flow in bifurcating channels is missing. This paper presents a description of the experimental setup for such measurement and statistically evaluated characteristics of the rotation and flips of micrometre-sized glass fibres. The results proved that there are significant differences in the rotations of fibres when compared to previously measured stationary flows.

The spray behaviour and droplet trajectories in realistic conditions are of crucial importance in many industrial, agricultural and chemical applications. Droplet characteristics and spray trajectory in chemical applications (e. g. flue gas scrubbing, CO2 capture in spray column) determine the amount of mass involved in the gas scrubbing process, mass trapped by the flow or attached to the walls. Knowledge of the droplet behaviour can improve a nozzle design and scaling, increase the process efficiency, minimize the process liquid and blow away the fraction. In this study, experiments with pressure swirl nozzle in cross–flow of air were performed at one nozzle injection pressure (0.5 MPa) and several cross–flow velocities (8, 16, 32 m/s). The results on droplet trajectories are compared with numerical results obtained by ANSYS Fluent. Two Lagrange approaches for spray modelling were used. Injection of droplet groups and Linearized Instability Sheet Atomization (LISA) model incorporated within ANSYS Fluent were used to represent the spray. The CFD results of spray penetration and droplet trajectories are compared with experimental data. A simple analytical model is able to well predict trajectories of large droplets, but fails to predict trajectories of small droplets. The LISA model yields a better accuracy for spray in cross-flow prediction.

The replication of atomizers by 3D printing technology is a new approach of producing the pressure swirl atomizers. The surface roughness of 3D printed products and manufacturing accuracy of the 3D printing process influence the atomization of the liquid. The high-speed visualization of a spray, produced by scaled 3D printed atomizer, was performed. The spray stability, cone angle and breakup length were determined. Scaled 3D printed atomizers were tested at equivalent pressures of 0.25, 0.5 and 1 bar. Non-dimensionless parameter, Reynolds number, was preserved for the scaled atomizer. The effect of the surface roughness of the tangential ports, swirl chamber and discharge orifice on atomization was assessed at non-scaled pressure swirl atomizer. The roughness of a swirl chamber was created by corundum and ballotin blasting. The inlet pressures of 2.5, 5 and 10 bar were tested.

Inhalation of pharmaceutical aerosols is a convenient way to treat lung or even systemic diseases. For effective treatment it is very important to understand air flow characteristics within respiratory airways and determine deposition hot spots. In this paper the air flow in trachea was investigated by numerical simulations. To validate these results we carried out particle image velocimetry experiments and compared resulting velocity fields. Simplified geometry of respiratory airways from oral cavity to 4th generation of branching was employed. Air flow characteristics were analysed during sinusoidal breathing pattern for light activity conditions (period 4 s and tidal volume 1 l). The observed flow fields indicated that the flow in trachea is turbulent during the sinusoidal flow except phases of flow turnarounds. The flow was skewed to front side of the trachea during inspiration and had twin-peak profile during expiration because of the mixing from daughter branches. The methods were compared and good agreement was found. This validation of CFD simulation can result into its further usage in respiratory airflow studies.