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A numerical model of the aerosol transport and deposition in human airways is presented. The model was acquired from a CT scan a living person and consist of 6-9 bifurcations giving around 100 terminations of the tree. The oral/nasal cavity was not modelled in the presented work. The deposition of the particles is given for two breathing regimes, the resting conditions with a tidal volume of 0.5 liter and 15 l/min ventilation with period of 4 sec/cycle and full exercise conditions with 3.33 liter tidal volume and 120 l/min minute ventilation with cycle period of 1.25 sec/cycle. The aerosol concentration was assumed 50 μg/m^3 distributed in the three size classes PM10, PM 5 and PM 1. The results shows deposition in different segments of the tracheo-bronchial tree as well as velocity profiles at different time steps of the breathing cycle.

The paper introduces results of computational fluid dynamics (CFD) simulations of water flow at the reactor pressure vessel (RPV) outlet and under the RPV head. Several CFD calculations of the steady-state and dynamic processes involving forced and natural circulation of coolant are presented in the paper. In the steady state regime, several calculations were performed for various number of the reactor coolant system (RCS) loops connected to the reactor and the results have been used to analyse the effect of the RCS configuration to the coolant flow at the reactor outlet and under the reactor vessel head. General flow patterns are described in the outlet part of the reactor and under the reactor vessel head and, also, the influence of a lower flow rate through the reactor on thermal homogeneity of coolant under the vessel head. Simultaneously, we discuss the influence of the coolant flow rate at the core outlet on the heat transfer from the under-head space. Unsteady calculation was also done for a reactor cool-down in the regime of natural circulation. The calculation conditions correspond with the data obtained from the experiments led in the frame of the cool-down process of VVER440 reactor at Mochovce nuclear power plant in 2003. In the calculations, the main attention was applied to establishing the basic trends in the cool-down of water content at the outlet part of the reactor and under the head of the reactor vessel.

This paper presents numerical simulations of the acoustic wave propagation phenomenon modelled via Linearized Euler equations. A meshless method based on collocation of the strong form of the equation system is adopted. Moreover, the Weighted least squares method is used for local approximation of derivatives as well as stabilization technique in a form of spatial ltering. The accuracy and robustness of the method is examined on several benchmark problems.

The paper deals with the stochastic generation of synthesized turbulence, which may be used for a generating of an inlet boundary condition for unsteady simulations, e.g. Direct Numerical Simulation (DNS) or Large Eddy Simulation (LES). Assumptions for the generated turbulence are isotropy and homogeneity. The described method produces a stochastic turbulent velocity field using the synthesis of a finite sum of random Fourier modes. The calculation of individual Fourier modes is based on known energy spectrum of turbulent flow, and some turbulent quantities, e.g. turbulent kinetic energy and turbulent dissipation rate. A division of wave number range of the energy spectrum determines directly the number of Fourier modes, and has a direct impact on accuracy and speed of this calculation. Therefore, this work will examine the influence of the number of Fourier modes on a conservation of the first and second statistical moments of turbulent velocity components, which are prespecified. It is important to ensure a sufficient size of a computational domain, and a sufficient number of cells for meaningful comparative results. Dimensionless parameters characterizing the resolution and size of the computational domain according to a turbulent length scale will be introduced for this purpose. Subsequently, the sufficient values of this parameters will be shown for individual numbers of Fourier modes.

The paper deals with the convergence problem of the SPH (Smoothed Particle Hydrodynamics) meshfree method for the solution of fluid dynamics tasks. In the introductory part, fundamental aspects of mesh- free methods, their definition, computational approaches and classification are discussed. In the following part, the methods of local integral representation, where SPH belongs are analyzed and specifically the method RKPM (Reproducing Kernel Particle Method) is described. In the contribution, also the influence of boundary conditions on the SPH approximation consistence is analyzed, which has a direct impact on the convergence of the method. A classical boundary condition in the form of virtual particles does not ensure a sufficient order of consistence near the boundary of the definition domain of the task. This problem is solved by using ghost particles as a boundary condition, which was implemented into the SPH code as part of this work. Further, several numerical aspects linked with the SPH method are described. In the concluding part, results are presented of the application of the SPH method with ghost particles to the 2D shock tube example. Also results of tests of several parameters and modifications of the SPH code are shown.

The paper deals with instigation of influence of air duct geometry on air jet direction in aircraft cabin ventilated by mixing ventilation. CFD approach was used for investigation and model geometry was based on small aircraft cabin mock-up geometry. Model was also equipped by nine seats and five manikins that represent passengers. The air jet direction was observed for selected ambient environment parameters and several types of air duct geometry and influence of main air duct geometry on jets direction is discussed. The model was created in StarCCM+ ver. 6.04.014 software and polyhedral mesh was used.

Thermal comfort and also reduction of energy requirements of air-conditioning system in vehicle cabins are currently very intensively investigated and up-to-date issues. The article deals with two approaches of modelling of car cabin environment; the first model was created in simulation language Modelica (typical 1D approach without cabin geometry) and the second one was created in specialized software Theseus-FE (3D approach with cabin geometry). Performance and capabilities of this tools are demonstrated on the example of the car cabin and the results from simulations are compared with the results from the real car cabin climate chamber measurements.

A rotating packed bed (RPB), as a device for mass transfer enhancement, can be divided into three main parts. An eye of a rotor, a packing, and an outer cavity. It has been reported that a contribution to the total mass transfer of the outer cavity can reach up to 30% of the whole device. Mass transfer is highly influenced by the droplet hydrodynamics and dimensions, hence the liquid dispersion from the outer surface of a metal foam packing was recorded with a high-speed camera. The recordings were analysed with an in-house MATLAB® code to determine the droplet dimensions, and with a PIVlab software to evaluate velocity fields. It has been found that the droplet dimensions and velocities were influenced primarily by a packing speed, as the higher packing speed resulted in a presence of the smaller droplets. Two peaks in histograms for the droplet diameters could be explained with a breakup theory of a liquid jet which breaks into large, mother, and small, satellite droplets. The droplet velocity corresponded to a peripheral velocity of the packing. A liquid flow rate influenced only the number of droplets dispersed from the packing.

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.

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 development of the human airways continues even after birth. During childhood, not only does the shape of the upper airway change, but also the way we inhale. The development of human upper airways and the mouth cavity stops at the age of five and after that, only changes in dimensions occur. This study aims to compare the difference in the deposition of spherical particles inhaled under the resting conditions in three various age periods: infant (10 months), children (5 years) and adult (25 years). For this purpose, new airway geometries in these developmental stages were created and constant inspiratory flow rates corresponding to resting conditions were studied. Simulations were performed using a CFD solver Star-CCM+, and turbulence was solved using a Large Eddy Simulation approach. The particle deposition was solved using the Lagrangian multiphase model. The results revealed significant differences in the size fractions of particles deposited in identical airway regions.

Majority of power producing, and industrial processes generate a significant amount of carbon dioxide (CO2). To reduce their CO2 emissions, CCS (carbon capture and storage) can be used. One of the ways for CO2 capture is rotating packed bed (RPB), which operates on a similar principle as an absorption tower. However, in the RPB, mass transfer rate is driven by a centrifugal force, hence the RPB could be much smaller than the absorption tower, which relay on gravitational force. Also, the internal design of the RPB could affect efficiency of CO2 capture. There are several types of packing design, such as raised mesh, Zigzag, metal foam, or wire mesh. This study is focused on testing and construction of a transparent wire mesh packing, which could be used for analyse of fluid behaviour inside the packing e.g., a flow character, a liquid hold up and a liquid-gas interfacial. The operating packing speeds in the experimental part were 300 rpm, 600 rpm, 1200 rpm and 1800 rpm. The operating liquid (water) was supplied by six plain orifice nozzles with 1.44 mm diameter. Water was supplied to the system in a range of liquid flow rates from 44 to 176 kg/h. This corresponds to the jet velocity of 1.25 – 5.00 m/s. The observed area was the entry of the water jet into the wire mesh, where the atomization is the most intense. For the measurement, a high-speed camera was used. It is evident from results that with the higher jet velocity, the penetrating distance is larger, and the atomization is more intense.

Heat transfer inside a cylinder and the cylinder head of a reciprocating compressor is responsible for the majority of thermodynamic losses in these devices. Both the magnitude and direction of the heat flux through the walls of those components change several times during a single revolution. They are directly dependent on the position of the piston and suction/discharge valves. A better understanding of these thermal processes could lead to better and more targeted cooling. This would result in higher efficiency of the reciprocating compressors. In this paper, two experimental methods for determining heat flux are used. The first method uses heat flux sensors to measure heat flux directly. The other one is focused on the indirect assessment of heat flux via surface-mounted thermocouples. To tie the measurement to the position of the crankshaft, both sensors are coupled to a rotary encoder. The rotary encoder sends a signal once per revolution when the piston is in the top dead center position to trigger signal acquisition. The results show signs of reaching a quasi-steady state and would most likely require sampling of the signal more times per revolution.

In certain applications where temperature changes rapidly, e.g., compressor cylinder or explosion chamber, it is necessary to obtain temperature data with a sample rate high enough to register the change, i.e., the temperature probe response time must be very low. Type E coaxial thermocouples with response time in the range of µs can be an example of such a temperature probe. This paper describes several approaches for high-frequency temperature data obtained using coaxial thermocouples. Individual approaches are described together, as well as their shortcomings. Furthermore, the possible method of data evaluation is discussed.

Aerosol particles like dust involved in the air can pass through the respiratory tract and can be deposited there. The long-term deposition of fine solid particles in the lower airways can stimulate lung diseases. In contrary, for the healing of certain lung diseases, the delivering of medicament’s to the lower airways is important. Computational Fluid Dynamics (CFD) enables to simulate the flow field and the particles deposition in the lungs. By this method, it is possible to identify the probability of reaching particles into the lower airways through the tracheo-bronchial tree. In this paper, the flow field in the child lungs (5-year-old) in a constant sedentary breathing regime was simulated using the Lattice Boltzmann Method (LBM) with the LES Smagorinsky turbulence model. To verify the calculated velocities by LBM in OpenLB software, the finite volume RANS simulation in Star-CCM+ was performed. The results showed the good agreement in the upper part of the airways. Some discrepancies were found in the lower part. Nevertheless, LBM and OpenLB were proven to be a capable tool to solve the air flow through the respiratory tract and will be used for particle deposition.

Liquid dispersion on a wire mesh is a phenomenon that is utilized in many industrial applications, such as rotating packed beds. It is a very simple method of liquid atomization without a need for complex nozzles. This research focuses on an elementary case of a liquid dispersion on a crossing of two wires. Experiments were carried out in a wind tunnel to elucidate the influence of counterflow air velocity on a liquid sheet and droplets. High-speed camera was used to capture the impact of droplets on the crossing. Images were then processed using MATLAB® addon PIVlab. The effect of the input parameters, including a liquid flow rate in the range of 3.8 to 12 kg/h and air flow velocity varying from 0 to 9 m/s on the angle and velocity of dispersed droplets downstream of the crossing, was investigated. Finally, a qualitative description of the dispersion was evaluated. Results show that with an increasing liquid flow rate, the droplets dispersed in a wider angle. On the other hand, the influence of the air counterflow is significant only for low liquid flow rates. The atomization rate, determined by the number of small droplets, was better for higher liquid flow rates.

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.

Respimat soft mist inhaler (SMI) is an inhaler producing a soft mist with low velocity. The liquid drug solution is emitted by the mechanical energy of compressed spring, so the device is propellant-free. This paper describes the measurement of particle fraction penetrating through the model of the upper respiratory tract (mouth cavity, pharynx, larynx trachea). The solution inside the cartridge was marked by fluorescein in order to evaluate the regional particle deposition in the model. After the exposition, segments of the model, as well as the filter, were washed out and the deposited fluorescein was extracted into water. The analysis showed that the fraction of particles penetrating through the upper respiratory tract was 64.7±6.7 %. However, the real inhalation pattern was not simulated and measurement was provided with continual “inhalation” without “exhalation”.

Computational fluid dynamics (CFD) was used to investigate new ways of air conditioning of a car cabin during summer conditions. Three different schemes of ventilation were considered: classical mixing ventilation (dashboard vents), large-area ceiling vents, and underfloor vents delivering air under the seats. The Star-CCM+ was used to carry out unsteady RANS simulations and resulting temperature and velocity fields were compared. Furthermore, the draft risk and age of air were evaluated for each scheme. For air conditioning of the cabin, mixing ventilation had the best results.

Study deals with liquid dispersion of water in unstructured wire mesh of rotating packed bed, experimentally investigated using high speed camera. Dispersed water in outer region of rotating packed bed were captured by high-speed camera and droplet size were investigated using image processing. Numerical simulations were performed on two – dimensional plane with similar geometry characteristics (diameter and distance between each wire). Volume of fluid method was used to describe a multiphase behaviour of phenomena and turbulence was modelled using k-epsilon model. Results of both were compared on basis of frequency distribution of individual size fraction of dispersed water in outer region of rotating packed bed and its velocities. Discussion was focused on possibility of 2D numerical investigation and possibility of its comparison with experimental measurement.

The development of organs in the human body does not end at birth. During the first five years of life, changes occur in the respiratory tract, not only in terms of its dimensions but also in the way it is used. Efforts to provide non-invasive treatment in the form of medical aerosols administered to children´s lungs during this period must be supported by knowledge of the flow pattern that significantly influences their transport and deposition. Research related to flow patterns in the adult human respiratory tract is quite widespread and the phenomena that occur during inhalation in different parts of the respiratory tract have been widely documented. In the case of the paediatric respiratory tract, research is relatively scarce due to the age of the patient and the desire to minimise interference with the paediatric organism. At the Brno University of Technology, we have the geometry of the airway of a ten-month-old infant, a scaled model of an adult to match the geometry of a five-year-old child based on scientific knowledge and also an adult model of the human respiratory tract. These geometries, together with knowledge of respiratory physiology were used to compare the changes in airflow behaviour that occur in the trachea during the first five years and compare it to fully developed adult human geometry. Computational Fluid Dynamics was used to investigate the model using a Large Eddy Simulation approach. The periods of life captured by the geometries differ not only in their dimensional difference but also in their approach to airway use. The impact of these differences has been captured in the paper.

Inhaled fibres can potentially cause inflammation of the lung tissue and interstitium which, after long-term exposure, may lead to lung cancer, malignant mesothelioma or pulmonary and pleural fibrosis. For risk reduction and correct setting of occupational hygiene regulations, it is important to be able to precisely calculate the fate of inhaled fibres depending on their physical characteristics and inhalation conditions. As there is a lack of experimental data on the orientation of fibres, a new test rig has been assembled for visualization and recording of flowing fibres in a replica of the human trachea. Fibres prepared from regular glass fibres produced commercially for blown thermal insulation have been processed, dispersed and introduced into the glass tube with dimensions of the trachea. Visualization was performed using a powerful LED light and a high-speed camera. Angles of the fibres have been evaluated for six different flowrates and the dependence of the angles on the flow Reynolds number was searched for. The angles of fibres agreed with expected values, i.e. only vertically and horizontally oriented fibres were recorded. However, the number of vertically and horizontally oriented fibres did not seem to be correlated with the flow Reynolds number.

The nature of fibre motion is much more complex than the motion of spherical particles. A complex model must be used for tracking of the fibre carried by the flow. The model must take into account the orientation of the fibre against the flow and solve the consequent rotation of the fibre. Description of such model can be found in this article. It is then used for simulation and analysis of fibre movement in a single planar bifurcation.

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.

This study deals with optimalization of rotating packed bed design using computational fluid dynamics approach. Comparison of three variants of liquid distributor were performed on 2D geometry. Turbulence was modelled using unsteady RANS approach and volume of fluid technique were used to simulate gas-liquid interphase. Results were compared on basis of liquid holdup evaluation.

Tracking of fibres in a fluid flow is much more complicated than tracking of spherical particles. In fibre motion, the orientation of fibre against the flow direction plays a very important role. In addition to the standard equation of motion, additional equations for orientation and angular velocity must be solved during the tracking of fibres. A mathematical model describing fibre motion is introduced in this work. Capabilities of this model are demonstrated through simulations of fibre transportation by air in a channel flow. The importance of the terms in the equation of angular velocity are discussed.

Particles exposed to an electric field experience forces that influence their movement. This effect can be used for filtration of air, or for size classification of aerosols. The motion of charged particles in a non-uniform electric field is called electrophoresis. Two processes are involved in this phenomenon: 1) charging of particles and 2) electrical mobility separation. If fibres are exposed to electrophoresis, they are separated on the basis of two parameters: diameter and length. Regrettably, as naturally occurring fibres are polydisperse both in diameter and length, the electrophoresis is not very efficient in length classification. In contrast, dielectrophoresis is the motion of electrically neutral particles in a non-uniform electric field due to the induced charge separation within the particles. As deposition velocity of fibres induced by dielectrophoretic force strongly depends on length and only weakly on diameter, it can be used for efficient length classification. Principles of length classification of conducting and non-conducting fibres are presented together with design of a fibre classifier. Lastly, images of motion of fibres recorded by high-speed camera are depicted.

The velocity field in the area behind the automotive vent was measured by hot-wire anenemometry in detail and intensity of turbulence was calculated. Numerical simulation of the same flow field was performed using Computational fluid dynamics in commecial software STAR-CCM+. Several turbulence models were tested and compared with Large Eddy Simulation. The influence of turbulence model on the results of air flow from the vent was investigated. The comparison of simulations and experimental results showed that most precise prediction of flow field was provided by Spalart-Allmaras model. Large eddy simulation did not provide results in quality that would compensate for the increased computing cost.

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 aim of the paper is to assemble a simulator for evaluation of thermal comfort in car cabins in order to give a feedback to the HVAC (heating, ventilation and air conditioning) system. The HW (hardware) part of simulator is formed by thermal manikin Newton and RH (relative humidity), velocity and temperature probes. The SW (software) part consists of the Thermal Comfort Analyser (using ISO 14505-2) and Virtual Testing Stand of Car Cabin defining the heat loads of car cabin. Simulator can provide recommendation for the climate control how to improve thermal comfort in cabin by distribution and directing of air flow, and also by amount of ventilation power to keep optimal temperature inside a cabin. The methods of evaluation of thermal comfort were verified by tests with 10 test subjects for summer (summer clothing, ambient air temperature 30 °C, HVAC setup: +24 °C auto) and winter conditions (winter clothing, ambient air temperature -5 °C, HVAC setup: +18 °C auto). The tests confirmed the validity of the thermal comfort evaluation using the thermal manikin and ISO 14505-2.

Pressure-swirl atomizers are used in a wide range of industrial applications, e.g.: combustion, cooling, painting, food processing etc. Their spray characteristics are closely linked to the internal flow which predetermines the parameters of the liquid sheet formed at the discharge orifice. To achieve a better understanding of the spray formation process, the internal flow was characterised using Laser Doppler Anemometry (LDA) and high-speed imaging in a transparent model made of cast PMMA (Poly(methyl methacrylate)). The design of the transparent atomizer was derived from a pressure-swirl atomizer as used in a small gas turbine. Due to the small dimensions, it was manufactured in a scale of 10:1. It has modular concept and consists of three parts which were ground, polished and bolted together. The original kerosene-type jet A-1 fuel had to be replaced due to the necessity of a refractive index match. The new working liquid should also be colourless, non-aggressive to the PMMA and have the appropriate viscosity to achieve the same Reynolds number as in the original atomizer. Several liquids were chosen and tested to satisfy these requirements. P-Cymene was chosen as the suitable working liquid. The internal flow characteristics were consequently examined by LDA and high-speed camera using p-Cymene and Kerosene-type jet A-1 in comparative manner.