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1

Numerical estimation of film thickness with an air-assisted spray gun

Baytok Yusuf Mert, Erek Aytunc, Saf Orcun

Engineering Transactions

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2023

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Vol. 71, iss. 2

241--263

EN

The main goal of this study is to present the effects of spraying parameters on the numerical evaluations of the fundamental behaviors of an air-assisted spray gun during the formation of child droplets in the spray flow field and material deposition on the target surface. For this purpose, first of all, the air-assisted spray gun geometry was created using the Solidworks software. Then, a computational domain with a 3D, unstructured grid structure was generated using the ANSYS-Workbench meshing tool. Numerical calculations were conducted using ANSYS-Fluent 2020-R2 commercial software. Different breakup models and their effects on the child droplet size were investigated. By coupling the Taylor analogy breakup (TAB) model and discrete phase model (DPM), the droplet size, trajectory, and coating thickness calculations were made under different atomizing air pressures. Also, the effects of spraying distance and droplet size on coating thickness and the critical Weber (We) number on the atomized particle diameter and particle speed were investigated. The results show that with the increase in atomizing air pressure, droplet sizes decrease and the film thickness on the center of the target surface and droplet speeds increases. Also, increasing the critical Weber number makes it more difficult to atomize the droplets.

2

Experimental and numerical analysis of blood flow in roughness impact-R test

Kopernik Magdalena, Kruczek Dawid, Kurtyka Przemysław, Pomorska Małgorzata, Major Roman

Acta of Bioengineering and Biomechanics

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2022

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Vol. 24, no. 3

120--133

EN

The present paper covers simulation of blood flow in a roughness impact-R test model to anticipate the hemodynamic conditions of adhesion of blood elements to the modified surface. It was performed using numerical modelling of this process. The aim of these simulations was to create a surface morphology that stimulates the adhesion of blood elements to the surface of base plate of impact-R test. Methods: The morphology of base plate of impact-R test was developed using a vacuum powder sintering of commercial purity titanium powder (CP-Ti) on Ti6Al7Nb substrate. The finite volume method (FVM) and disperse particle method (DPM) were applied to develop the target model of a roughness impact-R test. The morphology of modified surfaces was documented with digital microscope and SEM (scanning electron microscopy). Results: The impact-R test developed using the two-phase blood model performed on regularly structured base plate resulted in shear stress values higher than the analogous for the model lacking such modification. The most significant reduction in maximum values of shear stress occurred in case of the DPM model and especially in the model with regular structures. Conclusions: The proposed models are very effective in modeling of the analysis of blood flow in roughness impact-R test.

3

Discrete phase model of blood flow in a roughness microchannel simulating the formation of pseudointima

Kopernik Magdalena, Dyrda Karina, Kurtyka Przemysław, Major Roman

Acta of Bioengineering and Biomechanics

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2022

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Vol. 24, no. 1

132--144

EN

The goal of the present study was the development of discrete phase model to simulate the phenomenon of backfilling a morphologically complex surface by red blood cells (RBCs) in a flow microchannel and to anticipate the conditions of forming a pseudointima. The objective of the experimental studies that inspired the development of the simulation was to create a surface that stimulates the formation of the pseudointima layer. Methods: The finite volume method (FVM) and discrete particle method (DPM) were applied to develop the target model. In addition, a mixture model and a roughness model of bottom layer were tested in the present study to show their influence on simulation the phenomenon of backfilling a morphologically complex surface by RBCs in a flow microchannel. Results: Numerical models were developed including: a) FVM models to compare the effect of applying boundary conditions with/without roughness and cubes, as well as the analysis of their influence on blood velocity and shear stress; b) mixture models to compare the effect of applying different boundary conditions and cubes on computed results; c) DPM models to compare the effect of applying and not applying roughness as a boundary condition; d) DPM models with a morphologically complex surface and RBCs collisions to present RBCs concentration, velocity and time distributions during flow in a channel. Conclusions: The analysis carried out for the developed numerical models indicates that DPM model with cubes computes the best results. It also shows the backfilling of a morphologically complex surface of the bottom microchannel with RBCs.

4

Numerical simulation of solid-fluid 2-phaseflow of cutting system for cutter suction dredgers

Zhang M., Fan S., Zhua H., Han S.

Polish Maritime Research

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2018

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S 2

117--124

EN

The study of the flow characteristics of the solid-fluid two phase flow in the cutter suction dredger is very important for exploring the slurry formation mechanism and optimizing the operational parameters. In this study, standard k-ε model and Multiple Reference Frame are applied to numerically simulate flow field in and around the cutting system, then with the steady convergent result of the simulation as the initial condition, Discrete Phase Mode is used to solve the particle motion equation by fully coupling the continuous phase and the particles . The influence of suction flow velocity and cutter’s rotating speed on particles suction are analyzed, and effectively suctioned particles numbers are also quantitatively studied. The simulation result shows that the DPM model is able to simulate the movement of particles in and around the cutter suction dredger’s cutting system, in the fluid flow filed velocity vector and pressure distribution on different planes show different characteristics, and under higher suction velocity and lower cutter rotating speed more particles are suctioned into the suction inlet. The results can help better understand flow characteristics of solidfluid 2-phase-flow of cutter suction dredger’s cutting system, and provide theoretical support for relative system design and operational parameters optimization.

5

Phase Object Observation System Based on Diffraction Phase Microscopy

Babicz S., Stawarz-Graczyk B., Wierzba P.

Metrology and Measurement Systems

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2018

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Vol. 25, nr 1

213--221

EN

In the paper authors present a special measurement system for observing phase objects. The diffraction phas microscopy makes it possible to measure the dimensions of a tested object with a nanometre resolution. To meet this requirement, it is proposed to apply a spatial transform. The proposed setup can be based either on a two lenses system (called 4f) or a Wollaston prism. Both solutions with all construction aspects are described in the paper. To make a full analysis of the object shape the authors developed an accurate image processing algorithm, also presented in the paper.

6

Fundamental understanding of diesel-operated man riding vehicle DPM dispersion - a case study

Morla R., Godbole A., Karekal S., Bhattacharjee R. M., Balasubrahmanyam N.

Journal of Sustainable Mining

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2018

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Vol. 17, iss. 3

105--110

EN

In this paper, an attempt has been made to model DPM flow patterns in the vicinity of man riding vehicle(s) operating in a coal mine environment. The DPM flow patterns are modelled using the techniques of computational fluid dynamics (CFD) and validated using field experimental measurements. The models show that if the vehicle is stationary, DPM particles are dispersed towards the center of gallery. Beyond 20m downstream of the vehicle, the DPM particles occupy the entire cross-section of the roadway. If movement of the vehicle is considered, the miners may be exposed to a high concentration of DPM due to the engines running at full capacity and the resultant air flow induced by the movement of the vehicle.

7

Assessment of Diesel Particulate Matter Exposure of Underground Miners in Indonesia

Susanto A., Purwanto P., Sunoko H. R., Setiani O.

Journal of Ecological Engineering

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2018

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Vol. 19, nr 4

34--42

EN

In Indonesia, there are underground mines for mineral metal such copper (Cu) and gold (Au), built by tunneling towards the mineral location. The purpose of this study was to determine the mapping a concentration of diesel particulate matter (DPM) and assess the impact on health by severity measurement of airflow obstruction of the miners experiencing chronic obstructive pulmonary disease (COPD). The data of DPM were measured with NIOSH method no. 5040 and applied a geostatistical method in mapping concentration at the area of underground mining. A spirometric measurement was conducted to diagnose COPD that is done to the 314 miners. The results showed that the concentrations exceeding the permissible exposure limit (PEL) and spirometric measurement were found for 26 miners (8.3%) who experience COPD (post bronchodilator <0.70). The severity measurement of airflow obstruction of the miners experiencing COPD, severity of airflow limitation for moderate (GOLD 2) was obtained for 14 miners (54%); severe (GOLD 3) for 10 miners (38%) and very severe (GOLD 4) for 2 miners (8%). It can be concluded that the amount of DPM exposure against the severity of airflow limitation with COPD by 0.03, in which the other factors also affect the severity.

8

Investigating the Effect of the Opening Unit on the Airflow Field in Rotor Spinning

Jin Y., Zhu S., Cui J., Li J., Zhu Z.

Fibres & Textiles in Eastern Europe

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2017

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Vol. 25, no. 5 (125)

18--24

EN

The opening unit is an important device in a rotor spinning unit to comb fibres and remove trash. In this paper, numerical simulation is carried out to study the flow structure in the rotor spinning channel and the trash removal process in the trash removal unit. Firstly the effect of the opening unit on the airflow field in the rotor channel is investigated by singlephase simulation. The result shows that the effective area for fibre conveyance enlarges as the absolute value of negative pressure at the outlet increases, while it decreases as the opening roller speed increases. However, the effect of the negative pressure and the opening roller speed on the length of the vortex in the axial direction is quite small. Secondly the trash separation process in the trash removal unit is simulated using the Discrete Phase Model (DPM). Suitable rotational speeds of particles of different diameters are acquired. These results could provide a valuable reference for parameter selection in the trash-removal process.

PL

Jednostka otwierająca jest ważnym urządzeniem w przędzarce rotorowej służącym do rozczesywania włókien i usuwania odpadów. W artykule przeprowadzono symulację numeryczną mającą na celu zbadanie struktury przepływu w kanale przędzalniczym wirnika oraz procesu usuwania odpadów. Wpływ jednostki otwierającej na pole przepływu powietrza w kanale wirnika badano symulacją jednofazową. Wyniki wykazały, że efektywny obszar transportu włókien powiększa się, gdy wartość bezwzględnej wartości ujemnego ciśnienia na wylocie wzrasta, a zmniejsza się wraz ze wzrostem prędkości wału otwierającego. Jednakże wpływ podciśnienia i prędkość wału otwierającego na długość wiru w kierunku osiowym jest stosunkowo niewielka. Stwierdzono także, że proces separacji odpadów w jednostce usuwania odpadów jest symulowany przy użyciu modelu dyskretnego fazy (DPM). Otrzymuje się odpowiednie prędkości obrotowe cząstek o różnych średnicach. Wyniki te mogą stanowić cenny punkt odniesienia dla wyboru parametrów w procesie usuwania odpadów.

9

Identification and modelling of blood flow processes in section of large blood vessel using hybrid Euler-Lagrange multiphase approach

Knopek Artur

Archiwum Instytutu Techniki Cieplnej

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2016

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Vol. 1

53--80

EN

Computational fluid dynamics (CFD) in past known only in highly specialized technical engineering branch is nowadays one of main engineering tool in solving numerous complex problems in order to get crucial information and extend general knowledge in many fields. CFD allows to create new, more advanced systems and also optimize already created to enhance efficiency and/or reduce costs of production and operating. Actual situation demands from engineers to face difficult competition - fighting for minor fractions of efficiency due to construction and materials limitations. That operations do not concentrate only on that obvious disciplines like heat transfer, fluid dynamics or power-generation, but also new uncharted areas like automotive, chemical, aerospace, environmental engineering etc. One of that innovative field of CFD application is bio-engineering. In medicine, computer simulations can provide necessary, life-saving information with no interfere in patient body (in vivo), that allows to avoid later complications, application collisions and dangerous unpredictable after-effects. What more in several cases, in vitro analyses cannot be used through to life threats of treatment. The main objective of current project is to develop and test novel approach of accurate modelling of human blood flow in arteries. Currently available research reports do not cover the spatial interaction of individual blood phases and walls of blood vessels. Such approach could significantly reduce accuracy of such models. Proper simulations enriches general knowledge with specific details which could be crucial in early diagnosis of potential cardiac problems showing vulnerable zones (e.g. narrowed blood vessels). Such precise information are extremely difficult to obtain experimentally. Apart from multiphase concept of the project (that is considering every component of blood as separate phase assigning exceptional properties to each of them and determines relations between them) special attention was paid to the realism of geometry - considering the real system of the aortic segment (part of ascending aorta, aortic arch and part of thoracic aorta) including bifurcations. In addition a pulsating blood flow is being considered and implemented using built in UDF (User Defined Function) functionality of CFD code.

PL

Obliczeniowa mechanika płynów (ang. CFD – Computational Fluid Dynamics) znana niegdyś tylko w wysoce wyspecjalizowanej technicznie branży jest jednym z podstawowych narzędzi inżynieryjnych w rozwiązywaniu wielu złożonych problemów, celem zdobycia kluczowych informacji i poszerzenia wiedzy ogólnej w wielu dziedzinach. CFD pozwala na tworzenie nowych, bardziej zaawansowanych systemów oraz na udoskonalanie już istniejących – poprawiając ich wydajność i/lub obniżając koszty produkcji oraz eksploatacji. Aktualna sytuacja wymaga od inżynierów zmierzenia się w trudnej dyscyplinie – walce o ułamki wydajności z powodu ograniczeń materiałowych i konstrukcyjnych. Przedsięwzięcia te nie koncentrują się jedynie na oczywistych dyscyplinach, takich jak przepływ ciepła, mechanika płynów czy wytwarzanie energii, ale także na nowych, niezbadanych sferach jak inżynieria motoryzacyjna, chemiczna, kosmiczna czy środowiska itd. Jednym z innowacyjnych zastosowań CFD jest bio-inżynieria. W medycynie, symulacje komputerowe są w stanie dostarczyć niezbędnych, nierzadko ratujących życie informacji, bez ingerencji w ciało pacjenta (in vitro), co pozwala uniknąć późniejszych komplikacji, zagrożeń występujących w trakcie wprowadzania przyrządów w ciało pacjenta czy niebezpiecznych nieprzewidywalnych powikłań. Ponad to w wielu przypadkach metody in vivo są niemożliwe do zastosowania ze względu na zagrożenie życia pacjenta. Głównym celem powyższego projektu było stworzenie i testy innowacyjnego, dokładnego modelu przepływu krwi w ludzkiej aorcie. Aktualnie dostępne badania nie uwzględniają przestrzennych interakcji pomiędzy poszczególnymi fazami krwi i ścianami naczyń krwionośnych. Takie podejście zdecydowanie zmniejsza dokładność tego typu modeli. Odpowiednie badania wzbogacają wiedzę ogólną o dokładne informacje , które mogą okazać się kluczowe we wczesnym diagnozowaniu problemów układu sercowo-naczyniowego, wskazując na potencjalnie podatne obszary (np. kurczące się naczynia krwionośne). Tak dokładne informacje są trudno dostępne do uzyskania na drodze badań. Poza wielofazowa koncepcją projektu, który rozpatruje każdy komponent krwi jako oddzielną fazę, przyporządkowując poszczególne właściwości do każdej z nich i uwzględniając ich wzajemne relacje, szczególną uwagę zwrócono na realistykę geometrii – zakładając rzeczywisty układ aortalny (część aorty wstępującej, łuk aortalny i część aorty zstępującej) uwzględniający bifurkację. Ponadto wprowadzono do modelu przepływ pulsacyjny za pomocą wbudowanej wewnętrznej funkcji programu. (ang. UDF – User Defined Function).

10

Temperature-controlled oscillator and dedicated microcontroller for dynamic thermal management

Frankiewicz M., Kocanda P., Gal R, Kos A.

International Journal of Microelectronics and Computer Science

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2014

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Vol. 5, nr 2

81--86

EN

The paper describes UMC CMOS 0.18 pm (1.8 V) implementation of OctaLynx D microcontroller. The processor is 8-bit RISC structure with built-in Dynamic Thermal Management Unit cooperating with Temperature-Controlled Oscillator. The Dynamic Thermal Management Unit consists of clock source multiplexer, thermal interrupts control unit and special registers containing information of present chip temperature, oscillator frequency control signal and status/control bits. Processor core was written in Verilog hardware description language and designed in top-down technique while memories and analogue parts were designed in full custom technique. The system was fabricated and tested in the laboratory equipped with the thermal chamber. Some test results and software prepared for the microcontroller are presented.