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Symulacje CFD w przemyśle petrochemicznym

Gałęziowska Karolina, Grzywacz Robert, Michorczyk Piotr

Przemysł Chemiczny

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2025

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T. 104, nr 11

1185--1191

PL

Dokonano krótkiego przeglądu metod modelowania CFD w przemyśle petrochemicznym. Scharakteryzowano wybrane modele oraz wskazano przykłady ich zastosowania. Poruszono problemy i wskazano możliwe kierunki rozwoju.

EN

A review, with 23 refs., of pract. CFD modeling methods. In particular, models of multiphase flow, heat exchange, mixing, sorption, combustion and reaction kinetics were presented. Some issues and potential future development directions were discussed.

2

Design and structural analysis of an innovative grain dryer frame with integrated mass measurement

Łykowski Wiktor, Gierz Łukasz, Berdychowski Maciej, Modrzejewska-Sikorska Anna, Javorova Juliana

Journal of KONBiN

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2025

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Vol. 55, iss.1

17--27

EN

Seeds of crops such as rapeseed, corn, and sunflowers require post-harvest drying for proper storage. Inadequate seed moisture leads to the development of bacteria and fungi. Excessively high seed moisture content promotes the growth of microorganisms, including bacteria and fungi, while excessively low moisture content reduces seed viability. The average moisture content of corn during harvest is up to 35%, in the case of rapeseed, 12%, and in the case of wheat – 18%, while the recommended moisture content for grain storage is 14% for corn, 6% for rapeseed, and 14% for wheat. Mobile and stationary dryers are available on the market and can be used as flow or batch dryers. The work aims to develop an innovative concept of a dryer with strain gauge measurement of the mass of dried material and to analyze the strength of its main frame. The dryers available on the market do not have scales that could control weight loss. The project included the analysis of commercialized and available solutions on the market, the development of a 3D CAD model of the entire dryer with a hopper of 8 m3, and an analysis of the strength of the dryer's main frame using the finite element method. SolidWorks was utilized for 3D modeling and the subsequent FEM strength analysis. The results of the FEM analysis demonstrate the structural integrity of the dryer, suggesting its feasibility for commercial production.

PL

Nasiona roślin uprawnych, takich jak rzepak, kukurydza i słonecznik, wymagają suszenia po zbiorach w celu właściwego przechowywania. Niewystarczająca wilgotność nasion prowadzi do rozwoju bakterii i grzybów. Z kolei nadmierna wilgotność zwiększa zawartość szkodliwych mikrotoksyn fuzaryjnych. Średnia wilgotność kukurydzy podczas zbioru wynosi do 35%, w przypadku rzepaku 12%, a pszenicy 18%, podczas gdy zalecana wilgotność do przechowywania ziarna wynosi 14% dla kukurydzy, 6% dla rzepaku i 14% dla pszenicy. Na rynku dostępne są suszarnie mobilne i stacjonarne, które mogą być wykorzystywane jako suszarnie przepływowe lub porcjowe. Celem pracy jest opracowanie innowacyjnej koncepcji suszarni z pomiarem masy suszonego materiału za pomocą tensometru oraz analiza wytrzymałości jej głównej ramy. Dostępne na rynku suszarnie nie posiadają wag umożliwiających kontrolę ubytku masy. W ramach projektu przeanalizowano dostępne i skomercjalizowane rozwiązania, opracowano model 3D CAD całej suszarni z zasobnikiem o pojemności 8 m³ oraz przeprowadzono analizę wytrzymałości głównej ramy suszarni metodą elementów skończonych. Model 3D i analiza wytrzymałościowa zostały wykonane w programie SolidWorks. Opracowana suszarnia ma dużą szansę na komercjalizację. Wyniki analizy elementów skończonych wykazują integralność strukturalną suszarki, co sugeruje, że może być komercyjnie produkowana.

3

Aerodynamic characteristics of naca 16-006 airfoil under dynamic angle of attack variations

Maślanka Wojciech, Kachel Stanisław, Frant Michał

Journal of KONBiN

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2025

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Vol. 55, iss.4

1--25

EN

The aim of the article is to assess the influence of the angular speed on the aerodynamic characteristics of NACA 16-006 airfoil. In the numerical simulations, the flow was considered viscous, compressible, and turbulent (the SST k-ω turbulence model was applied). In the initial steady-state calculations, three structured computational meshes were evaluated, all providing consistent results with experimental data. The study mainly focused on unsteady simulations, in which the airfoil’s angle of attack was changed from 0° to 5° at specified constant angular velocities. The time courses of the lift, drag and pitching moment coefficients, as well as airflow parameters around the airfoil were investigated. The study facilitates the selection of a suitable method for evaluating the effectiveness of an all-moving stabilizer of a cruise missile model.

PL

Niniejszy artykuł ma na celu ocenę wpływu prędkości kątowej na wybrane charakterystyki aerodynamiczne profilu NACA 16-006. W badaniach numerycznych przepływ był rozpatrywany jako lepki, ściśliwy i turbulentny (zastosowano model turbulencji SST k-ω). We wstępnych obliczeniach stacjonarnych wykorzystano trzy strukturalne siatki obliczeniowe, spośród których wszystkie zapewniały dobrą zgodność wyników z danymi doświadczalnymi. W głównej części badań przeprowadzono symulacje niestacjonarne, w których kąt natarcia zmieniał się od 0° do 5° z określonymi stałymi wartościami prędkości kątowej. Przeanalizowano przebiegi czasowe współczynników siły nośnej, siły oporu i momentu pochylającego, a także parametry przepływu w pobliżu profilu. Badanie jest istotne w kontekście wyboru odpowiedniej metody oceny efektywności usterzenia płytowego modelu pocisku manewrującego.

4

CFD simulations and NEDC tests for the original and replacement selective catalytic reduction system

Kurzydym Damian

Combustion Engines

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2025

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R. 64, nr 2

58--71

EN

The purpose of this study was to perform both experimental and computational investigations on the selective catalytic reduction (SCR) system in passenger cars equipped with compression ignition (CI) engines. The study involves a comparison of results obtained for two separate SCR systems: an existing one and a newly developed system. The newly designed SCR system is intended for implementation in the spare parts market (aftermarket) and includes the creation of a custom mixer design. This research analyzed multiple SCR systems and mixers under varying operating conditions. Various factors were considered, including the examination and evaluation of gas distribution and nitrogen oxide reduction. The multiphase computational fluid dynamics analyses were conducted using the ANSYS Fluent software. A detailed assessment was carried out for the sequential processes occurring within the system. The final version of the replacement SCR system was analyzed in relation to the original system supplied by the original equipment manufacturer (OEM). The implementation of the new mixer in the replacement SCR system led to slightly reduced NOx emissions, as validated by emission tests (NEDC) performed in a car on a chassis dynamometer within a certification unit.

5

Impact of aging on anterior segment morphology and aqueous humor dynamics in human Eyes: Advanced imaging and computational techniques

Karimi Alireza, Darche Marie, Stanik Ansel, Razaghi Reza, Mirafzal Iman, Hassani Kamran, Hassani Mojtaba, White Elizabeth, Gantar Ivana, Pagès Stéphane, Batti Laura, Acott Ted S., Paques Michel

Biocybernetics and Biomedical Engineering

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2025

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Vol. 45, iss. 1

62--73

EN

Objective: Aging results in significant structural and functional changes in the anterior segment of the eye, influencing intraocular pressure (IOP) and overall ocular health. Although aging is a well-established risk factor for primary open-angle glaucoma, a leading cause of irreversible blindness, the specific mechanisms through which aging drives morphological changes in anterior segment tissues and affects aqueous humor dynamics remain incompletely understood. Methods: In this study, we employed cutting-edge light sheet fluorescence microscopy (LSFM) to capture high-resolution, volumetric images of cleared human donor eyes’ anterior segment tissues. This advanced imaging enabled a comprehensive morphological analysis of key parameters, including central and peripheral corneal thickness (CCT and PCT), iris thickness, anterior chamber area (ACA), and ciliary body area (CBA). By integrating these morphological parameters with computational fluid dynamics (CFD) models, we analyzed aqueous humor dynamics across n = 6 female human donor eyes, spanning a wide age range of 5 to 94 years (all of Caucasian descent). Results: The CCT and PCT demonstrated thinning with age, accompanied by a reduction in ACA. In contrast, the CBA remained relatively stable across all age groups. Computational fluid dynamics analysis showed a decline in aqueous humor velocity and wall shear stress, with younger eyes exhibiting higher velocities and shear stress, compared to older eyes. Conclusion: These findings emphasize the value of integrating LSFM and CFD approaches to provide a detailed understanding of how aging impacts the anterior segment and its fluid dynamics. This study contributes to the understanding of age-related ocular changes, highlighting the importance of considering these changes in the diagnosis and management of age-related eye diseases.

6

Flow visualization of flue gases in multi-tube electrostatic precipitators using CFD simulations

Čajová Kantová Nikola, Backa Alexander, Belány Pavol, Čaja Alexander, Jandačka Jozef

System Safety : Human - Technical Facility - Environment

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2024

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Vol. 6, iss. 1

201--208

EN

Particulate matter capture is a necessary concern for safeguarding human health and quality of life. This article focuses on enhancing particulate matter capture efficiency via electrostatic precipitation. It deals with expanding the fundamental principle of the single electrode in chimney tubular precipitator to a configuration with multi-tubular precipitation chambers with the aim of increasing the collection area and consequently enhancing the overall efficiency of the separator. The velocity distribution of flue gases was observed through Computational fluid dynamics using Ansys Fluent. The collection area for each proposed separator was calculated, including its enlargement, and the flow uniformity of flue gases through the tubes was assessed. Increasing the number of tubes from one to three resulted in 1.3 times an increase in the collection area. Further expansions to 4, 5, and 7 tubes led to increases of 1.6, 1.7, and 2.1 times, respectively. It was found that due to non-uniform flow distribution through the tubes, the flue gas velocities varied, with values ranging from 0.186 to 1.178 m. s-1 . Non-uniform gas flow prevents full utilization of the separator potential, thereby reducing its efficiency. For uniform flow, it would be appropriate to seek a suitable solution for a flow straightener. Additionally, the high particle velocities should be avoided to prevent particles from being carried out of the stack with the flue gas, allowing sufficient time for capture.

7

Uszkodzenia korozyjne wysokotemperaturowe w kolektorze rurowego wymiennika ciepła wynikające z niekorzystnych warunków przepływu i miejscowego przegrzania : analiza CFD

Parol Filip, Pawlicki Jakub

Przemysł Chemiczny

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2024

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T. 103, nr 12

1473--1478

PL

Przedstawiono wyniki analiz przepływowo-strukturalnych CFD kolektora wraz z początkowym odcinkiem rurek wymiennika ciepła konstrukcji ALSTOM. Analizy termiczno-przepływowe są częścią kompleksowych badań nad przyczynami uszkodzeń rurek wewnętrznych, spowodowanych szybko postępującą korozją od strony przestrzeni wodnej w okolicy połączenia z dnem sitowym. Przeprowadzono je na podstawie wcześniej wykonanych analiz materiałowych i procesowych. Badania materiałowe wykazały, że przyczyną uszkodzenia rur kotła była wysokotemperaturowa korozja w środowisku woda-para. Na podstawie analizy procesów technologicznych stwierdzono prawdopodobieństwo niewystarczającego odgazowania w deaeratorze oraz możliwe nagromadzenie osadów korozyjnych. Analizy termiczno-przepływowe wskazały na występowanie zastojów przepływu za częścią rurek wymiennika i pokrywanie się ich obszarów z typowymi miejscami uszkodzeń. Wykonano symulację uwzględniającą obecność warstwy korozyjnej na części powierzchni rurki i zaobserwowano znaczący wzrost temperatury w miejscach korozji.

EN

CFD flow-structural anal. of the manifold along with the initial section of the heat exchanger tubes, designed by ALSTOM were carried out to det. the causes of internal tube damage caused by rapidly progressing corrosion from the water side near the connection to the tube sheet. Flow-thermal anal. showed the occurrence of flow stagnation behind some of the heat exchanger tubes. Material tests showed that the cause of the boiler tube damage was high-temperature corrosion in a water-steam environment. A simulation was carried out taking into account the presence of a corrosion layer on part of the tube surface, revealing a significant increase in temp. in the corrosion areas.

8

Analiza egzergii i efektywność energetyczna systemów pomiarowych dla mediów ściśliwych opartych na dyszy ISA

Wołosz Krzysztof J.

Przemysł Chemiczny

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2024

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T. 103, nr 12

1487--1490

PL

W obliczu rosnących kosztów energii analiza egzergii staje się kluczowa dla zwiększenia efektywności energetycznej, szczególnie w sektorach przemysłowych wykorzystujących parę wodną. Badanie koncentruje się na ocenie strat egzergii w systemach nieustalonych i ściśliwych, przy zastosowaniu zaawansowanych technik symulacyjnych, takich jak OpenFOAM CFD. Wykorzystując twierdzenie o transporcie Reynoldsa, analiza zapewnia wgląd w straty jakości energii i efektywność pomiaru w systemach przemysłowych. Dokładność pomiaru wyznaczono wg normy, przez co wyniki oparte są na wiarygodnych wnioskach. Badanie podkreśla potrzebę zmiany założeń w projektowaniu i funkcjonowaniu systemów pomiaru strumienia masy dla mediów ściśliwych. Potrzeba ta wynika z możliwego do osiągnięcia zwiększenia jakości transportowanej energii, która to jakość jest mierzona jako wartość egzergii strumienia płynu.

EN

Simulation studies on the detn. of the amt. of energy and exergy in a flowmeter based on the measurement of the pressure difference at a measuring nozzle installed in a steam pipeline were presented. The simulation was performed in the CFD OpenFOAM program using the k-ω-SST 2006 turbulence model. The amt. of total stream energy and exergy losses in the measuring section of the steam flow through the measuring element was detd. A decrease in energy qual. in mass flow measurement systems was demonstrated.

9

Experimental and Numerical Determination of the Aerodynamic Characteristics of a Cruise Missile Model

Maślanka Wojciech, Kachel Stanisław, Frant Michał

Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa

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2024

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Vol. 15, Nr 2 (56)

37--46

EN

A model of a cruise missile was tested in symmetrical air flow in a low-speed wind tunnel of the Military University of Technology (Warsaw, Poland). A virtual model of the missile was developed, and the geometry of the computational domain was built in the CAD environment of the ANSYS computational software suite. The domain was discretised in the ANSYS Meshing application, creating a hybrid computational mesh. Boundary conditions were determined in the ANSYS Fluent application, and physical (turbulent compressible flow) and numerical models were selected. Calculations were performed for three different turbulence models - Spalart-Almaras, realizable k-ε, and SST k-ω - and the results were compared to find the model providing the best convergence with in-tunnel measurements.

PL

W tunelu aerodynamicznym małych prędkości Wojskowej Akademii Technicznej przeprowadzono badania modelu pocisku manewrującego w opływie symetrycznym. Opracowano wirtualny model pocisku i zbudowano geometrię domeny obliczeniowej w środowisku CAD pakietu obliczeniowego ANSYS. Domenę poddano dyskretyzacji w programie ANSYS Meshing, w wyniku czego utworzona została hybrydowa siatka obliczeniowa. W programie ANSYS Fluent określono warunki brzegowe, oraz dobrano modele fizyczne (opływ turbulentny, ściśliwy) i numeryczne. Obliczenia przeprowadzono dla trzech różnych modeli turbulencji - Spalart-Almaras, realizable k-ε, oraz SST k-ω, a wyniki porównano wskazując model zapewniający najlepszą zbieżność z pomiarami tunelowymi.

10

Studying the influence of the turbulence model on the aerodynamic characteristics of a cruise missile model

Maślanka Wojciech, Kachel Stanisław, Frant Michał

Journal of KONBiN

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2024

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Vol. 54, iss. 3

1--24

EN

The article presents the study of the turbulence model’s influence on aerodynamic characteristics of a cruise missile model obtained during numerical calculations conducted using ANSYS Fluent Release 2023R1 software. Three turbulence models (i.e. Spalart-Allmaras, realizable k-ε and SST k-ω), as well as three computational meshes with a different refinement in a boundary layer region, were investigated. The results were analyzed and compared to characteristics obtained experimentally in the low-speed aerodynamic tunnel at the Military University of Technology (Warsaw, Poland).

PL

W artykule przedstawiono badanie wpływu modelu turbulencji na charakterystyki aerodynamiczne modelu pocisku manewrującego, uzyskane na drodze obliczeń numerycznych w programie ANSYS Fluent Release 2023R1. Zastosowano trzy modele turbulencji (Spalart-Allmaras, realizable k-ε oraz SST k-ω), jak również trzy siatki obliczeniowe, różniące się zagęszczeniem elementów w rejonie warstwy przyściennej. Wyniki poddano analizie oraz porównano z charakterystykami uzyskanymi na drodze badań eksperymentalnych w tunelu aerodynamicznym małych prędkości Wojskowej Akademii Technicznej (Warszawa, Polska).

11

Mesh suitability for CFD simulations performed on axial compressor airfoil cascades

Tater Adam, Mačák Pavel, Kovář Patrik

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2024

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Vol. 72, nr 2

art. no. e148873

EN

In the presented paper, two different meshing strategies are compared to show the accuracy advantage of properly constructed mesh. For this purpose, it was necessary to automatize simulation process, in order to perform a number of calculations without the necessity of user interaction. Later, a method of results extrapolation as well as a way of judging mesh quality are introduced for more throughout comparison of presented discretization strategies. The latter method, called grid convergence index, is also used to calculate probability range of accurate result. To conclude, outcomes of this study are in agreement with general opinon on pracitces for an accurate CFD result. Structured O-type mesh with refinement at wall boundaries (often referred to as “inflation layers”) performs better than simple free mesh.

12

On the prediction of the effect of bi-ventricular assistance after cardiac explantation on the vascular flow physiology: A numerical study

Marcel Louis, Specklin Mathieu, Kouidri Smaine, Lescroart Mickael, Hébert Jean-Louis

Biocybernetics and Biomedical Engineering

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2024

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Vol. 44, no. 1

105--118

EN

Heart failure is a chronic and progressive condition characterized by the heart’s inability to pump sufficient blood to meet the body’s metabolic demands. It is a significant public health concern worldwide, associated with high morbidity, mortality, and healthcare costs. For advanced heart failure cases not responding to medical therapy, heart transplantation or mechanical circulatory support with ventricular assist devices (VADs) can be considered. In the specific case of bi-ventricular heart failure a replacement of both ventricles is required. In this context a Total Artificial Heart (TAH) may be proposed as a bridge to transplant solution. Additionally, bi-ventricular assist devices (BiVADs) are available to support both ventricles simultaneously. However Bi-ventricular heart failure management is difficult with poor outcomes. New surgical procedures appear to propose solutions after both ventricle failure. One of these intervention uses two continuous-flow VADs as a total artificial heart after cardiac explantation due to myocardial sarcoma. Unfortunately, this procedure makes patient management very difficult as pulmonary pressures and flow rate are no longer measurable after the surgical procedure. The setting of both pumps is hence a complex task for patient management. This article aims at helping clinicians on patient management undergoing double assistance after cardiac explantation by predicting the different outcomes on the vascular grid for all the possible rotational speed combination using a lumped model. Results provide a range of both pump operating conditions suitable for delivering a physiologically adapted flow to the vascular grid when combined with hypotensive treatments.

13

Evaluation of wind effects on buildings using design codes and numerical wind tunnel tests

Hossain Imam, Islam Jahidul, Amin Al

Structure and Environment

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2023

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Vol. 15, no. 2

73--81

EN

The evaluation of wind effect on the regular shape and simple diaphragm buildings and structures due to wind load has been calculated by several international codes and standards where wind gust nature and dynamic effect could not capture. Bangladesh National Building Code (BNBC) provides the tools for engineers to calculate the wind pressures for the design of a regular-shaped structure with a height to width ratio of less than 5.0, a simple diaphragm, and no unusual geometrical irregularity. If these conditions do not satisfy a wind tunnel testing is required. In this study, a comparative study between two codes in Bangladesh (BNBC-2006 and BNBC-2020), and wind tunnel test results are conducted. An investigation is carried out on four typical buildings with variable heights located within Dhaka, Bangladesh. A computational fluid dynamics (CFD) program RWIND is used to calculate the wind loads on buildings and are compared with those obtained by Bangladesh National Building Codes. Storey shear of four different building models is compared. Between BNBC-2006 and BNBC-2020, there is up to a 53% difference in storey shear. Whereas, up to 30% variation in storey shear is observed between the numerical wind tunnel test data and the data calculated using the BNBC-2020 equations. Finally, this study will help in improving BNBC code provisions for wind load calculations.

PL

Kalkulację wpływu wiatru na budynki i budowle o regularnych kształtach i prostych konstrukcjach pod obciążeniem wiatrem przedstawiono w kilku normach międzynarodowych, w których jednak nie uwzględniono charakteru podmuchów wiatru i efektu dynamicznego. Bangladeska Krajowa Norma Budowlana (BNBC) zapewnia inżynierom narzędzia do obliczania ciśnienia wiatru przy projektowaniu konstrukcji o regularnym kształcie, o stosunku wysokości do szerokości mniejszym niż 5,0, prostej konstrukcji oraz bez nietypowych nieregularności geometrycznych. Jeśli warunki te nie są spełnione, wymagane jest przeprowadzenie testów w tunelu aerodynamicznym. W niniejszym opracowaniu przeprowadzono badanie porównawcze między dwiema normami obowiązującymi w Bangladeszu (BNBC-2006 i BNBC-2020) oraz wynikami testów w tunelu aerodynamicznym. Badanie przeprowadzono na czterech typowych budynkach o różnej wysokości zlokalizowanych w Dhace w Bangladeszu. Program RWIND do obliczeń i symulacji dynamiki płynów (CFD) został wykorzystany do obliczenia obciążeń wiatrem na budynkach i porównany z wynikami uzyskanymi według bangladeskich norm budowlanych. Porównano ścinanie kondygnacji czterech różnych modeli budynków. W tym względzie różnice pomiędzy BNBC-2006 i BNBC-2020 wynoszą do 53%. Natomiast między danymi z numerycznego testu w tunelu aerodynamicznym a danymi obliczonymi przy użyciu równań BNBC-2020 zaobserwowano do 30% różnic w odniesieniu do ścinania kondygnacji. Badanie to pomoże też ulepszyć przepisy norm BNBC dotyczące obliczeń obciążenia wiatrem.

14

CFD and experimental investigation of the impact of dimensional modifications on wind pressure coefficient distribution

Ali Ramjan, Anam Iftekhar, Yoshida Shigeo

Structure and Environment

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2023

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Vol. 15, no. 4

208--216

EN

The sway of tall buildings in the wind is a fascinating and crucial consideration for professionals in the structural, environmental, and architectural fields. Previous research has related wind pressure to building load and natural ventilation, but few studies have looked at how building dimensions impact wind pressure. This study examined wind pressure coefficient distributions within and around several rectangular-shaped high-rise buildings using experimental and computational fluid dynamics approaches. The height-to-width ratio and height-to-thickness (length) ratio significantly affected the wind characteristics of buildings. The windward side with a narrower width experienced higher wind pressure, while the larger leeward side experienced a more negative wind effect. Wind pressure coefficient distribution varies with decrease in the side ratio. However, the side ratio of the building had little influence on positive wind pressure at wind incidence angle of 0°, which was a surprising finding. Pressure coefficients were evaluated and compared with standards by measuring fluctuating wind pressures at pressure points on all surfaces of models, and then calculating the mean, maximum, minimum, and r.m.s. values of these coefficients.

PL

Kołysanie się wysokich budynków pod wpływem wiatru jest fascynującym i kluczowym zagadnieniem dla specjalistów w dziedzinie konstrukcji, ochrony środowiska i architektury. W niniejszym artykule zbadano rozkłady współczynnika parcia wiatru wewnątrz i wokół kilku budynków wysokich o kształcie prostokąta, stosując metody eksperymentalne i numeryczne (obliczeniowa dynamika płynów). Stosunek wysokości budynku do jego szerokości oraz stosunek wysokości budynku do jego grubości (długości) miały znaczący wpływ na charakterystykę oddziaływania wiatru. Większe ciśnienie wiatru odnotowano po stronie nawietrznej o mniejszej szerokości, podczas gdy na większej ścianie od strony zawietrznej oddziaływanie wiatru było bardziej negatywne. Rozkład współczynnika parcia wiatru zmienia się wraz ze spadkiem stosunku boków. Jednak stosunek ten miał niewielki wpływ na dodatnie ciśnienie wiatru przy kierunku wiatru 0°, co było zaskakującym odkryciem. Współczynniki ciśnienia zostały ocenione i porównane z podejściem normowym poprzez pomiar zmiennego ciśnienia wiatru w punktach parcia na wszystkich powierzchniach modeli, a następnie obliczenie średnich, maksymalnych, minimalnych i średnich kwadratowych wartości tych współczynników.

15

Preliminary analysis of catenoid chimney cooling towers

Wiśniowski Maciej, Walentyński Robert, Cornik Dawid

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 6

art. no. e147341

EN

Optimization plays an important role in scientific and engineering research. This paper presents the effects of using the catenoidal shape to design the structure of a chimney cooling tower. The paper compares some geometrical variations of the catenoid with the reference existing hyperboloidal structure. It also compares internal forces, deformation and stability of the catenoidal structure. The comparison shows some predominance of the catenoid over the popular hyperboloid structure of the shell. The paper attempts to find an optimal shape of the cooling tower in order to reduce the amount of material and labor. The paper utilizes engineering tools and the designing process for chimney cooling towers.

16

Experimental and numerical analyses of airflow around two cylinders angled to the direction of wind

Padewska-Jurczak Agnieszka, Szczepaniak Piotr, Walentyński Ryszard

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 1

art. no. e144578

EN

The analyses aim to determine aerodynamic force coefficients in the case of airflow around two smooth or rough cylinders positioned at different angles to the direction of wind velocity. Such systems, for instance, may be part of a tubular water slide. The results were compared with the values of the interference coefficient of the cylinders arranged in a row included in Eurocode EN 1991 part 4. The aerodynamic forces of the cylinder systems were determined on the basis of experimental tests conducted in a wind tunnel. To verify the above results, CFD (computational fluid dynamics) simulations were prepared. An important observation is that for the angle of yaw β = 0◦, the negative component of the lift force (lateral) fy is shown, while for the other cases, the situation is opposite and the lateral force points outside the gap (upward). The second is that the results of aerodynamic drag for rough cylinders arranged in a row and calculated according to EN 1991 part 4 may be underestimated. The flow around the pair of smooth cylinders is quite different from that of the rough ones, because during the experiment the first falls into the critical flow regime, while the second has supercritical characteristics.

17

Influence of the position of the distal pressure measurement point on the Fractional Flow Reserve using in-silico simulations

Agujetas Rafael, Ferrera Conrado, González-Fernández Reyes, Nogales-Asensio Juan M., Fernández-Tena Ana

Biocybernetics and Biomedical Engineering

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2023

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Vol. 43, no. 1

69--81

EN

Coronary stenosis is mainly responsible for myocardial ischemia as the blood supply to a portion of the heart stops or is severely reduced. The Fractional Flow Reserve is the benchmark for the hemodynamic significance assessment of coronary stenoses. Its value is employed as a gatekeeper/planning tool for revascularization in clinical practice. Non-invasive alternatives have been successfully proposed to guide cardiologists. However, simulation values are not accurate enough in the 0.75-0.85 range, so invasive Fractional Flow Reserve should be used. Several authors argue about where distal pressure should be measured. Therefore, our aim is to use simulation to assess how this value changes and to detect the correct measurement region. First, we have adjusted the simulation method to the segmentations of two patients whose invasive Fractional Flow Reserve is known. We then extended our analysis to four patients and obtained the simulated value at multiple points distal to the stenosis. This is an advantage over invasive measurements, whose locations are restricted. The results are also essential for locating the best region for invasive distal pressure measurements. We propose a hybrid invasive and in-silico procedure that would avoid false results and prevent cardiologists from making erroneous clinical decisions.

18

Prediction of cavitation inside mini-sac Diesel injector nozzle using computational fluid dynamics

Bansode Vaibhav, Verma Munna, Pandhare Amar, Shinde Sandip

Journal of Mechanical and Energy Engineering

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2022

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Vol. 6, No 1

7--12

EN

The performance of the internal flow of the fuel injector is impeded by several factors. The nozzle is one of the factors, being typically about a millimeter long and a fraction of a millimeter in diameter. Cavitation inside the diesel injector nozzle is associated with local pressure distribution. At flow areas with sharp corners, the pressure may locally drop below vapour pressure. The aim of this study is to assess the impact of turbulence and cavitation models on the prediction of flow in diesel injection nozzle. In the present study, an analysis of an existing 6 hole mini-sac diesel injector nozzle is carried out using a CFD package. The main objective of the research is to design a nozzle to avoid cavitation and to find out the contribution of different parameters through parametric study. Cavitation is a complex phenomenon whose appearance depends on the physical as well as flow properties of the flowing substance. Thus, for a better visualization of cavitation, a 3D CFD simulation of mini-sac injector nozzle is carried out. An analysis of a single nozzle hole of a mini-sac diesel injector nozzle is considered for the analysis, as the flow is uniformly distributed through each nozzle. As the three-dimensional geometry of mini-sac nozzle is complicated, therefore tet/hybrid element with T-Grid meshing scheme is used, for good surface meshing. The analysis is carried out at injection pressure of 5 00 bar. The CFDresults are validated against test data with the maximum deviation for the mass flow rate of 8.67% at full needle lift.

19

Modeling of the microclimate in the work environment with the use of numerical methods

Kosiń Mariusz

Budownictwo o Zoptymalizowanym Potencjale Energetycznym

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2022

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Vol. 11

57--63

EN

The article presents modeling of the work environment microclimate using numerical methods. The numerical models adopted for the calculations were based on an office located in the building of the Faculty of Civil Engineering of the Czestochowa University of Technology. Six computational variations were made that differed in the heating method, air supply and ventilation. The results of the numerical analysis for one of the models were compared with the test in the assumed measuring point recording temperature and relative humidity. The per-formed numerical analysis allows for a relatively quick assessment of the influence of the adopted boundary conditions on the formation of the microclimate in the work environment.

20

Influence of cavity edges shape on flow induced noise

Łojek Paweł, Suder-Dębska Katarzyna, Mach Michał

Vibrations in Physical Systems

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2021

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Vol. 32, nr 1

art. no. 2021110

EN

In this paper, impact of the cavity shape on flow-generated noise is analysed. As reference model, the classic rectangular cavity with perpendicular corners was used. The impact of both upstream and downstream edges was analyzed. In this paper, authors used hybrid method, where the flow was computed by means of Spalart-Allmaras Detached Eddy Simulations (DES) model, and the acoustic wave propagation was calculated by Curle acoustic analogy.