Computational Fluid Dynamics (CFD) modelling and simulation

In many technical and industrial applications, the creation of hybrid nanofluids is an enormous idea. It is widely used in a variety of engineering applications, including heat exchangers, generator cooling, nuclear system cooling, and applications requiring strong thermal conductivity and a wide absorption range. In this article, we discussed the unsteady magnetohydrodynamics (MHD) free convection flow using a hybrid nanofluid of aluminum oxide/copper with water (Al2O3/ Cu-H2O) to look into mixed convection in an inclined porous medium cavity that contains a triangular heated obstruction. Finite element method (FEM) based on the Galerkin weighted residual approach is used to solve the governing partial differential equations (PDEs) along with boundary conditions. Numerous parameters, including Hartmann number ((100 0), Ha dimensionless time (0.1, 0.1, 1),  = and Darcy number 3 10 Da-= yield numerical results. In addition, the Darcy-Brinkman-Forcheimer comprehensive technique is being used to illustrate fluid flow in porous medium. A significant impact on streamlines, isothermal lines, and both the average fluid temperature inside the enclosure and the average Nusselt number at the heated surface has been found.

The study focuses on the combination of two numerical approaches that are typically not used together in this manner. The first is a well-established partitioned fluid-structure interaction (FSI) simulation methodology relying on a finite-volume fluid solver for curvilinear, block-structured, body-fitted grids written in the Arbitrary Lagrangian-Eulerian (ALE) formulation, and a finite-element solver for the structural analysis. The second approach is an immersed boundary (IB) method employing a continuous and direct forcing strategy. The IB method, often applied to Cartesian grids, is also referred to as an approach to simulate fluid-structure interactions. In this study, both methods are combined to exploit their respective advantages in simulating a complex flow problem. The coupled FSI problem involves the interaction of a thin, flexible structure deforming under the dynamic load of a wind gust (task 1). The gust itself is generated by an artificial wind gust generator, which includes a paddle that partially obstructs the wind tunnel's outlet, thereby defining an FSI problem of its own (task 2). For task 1, the classical partitioned ALE approach is employed, while the IB method is more appropriate for task 2. Using available experimental measurement data for both the fluid flow and the structural deformation, the combined simulation framework is first validated for the case without gust. In a second step, the more challenging FSI problem of discrete gusts impacting the T-structure is thoroughly analyzed and the predicted data are compared with the available measurement data. For both cases without and with gusts, a very good agreement between simulation and experiment is achieved, which justifies the chosen approach.

This thesis investigates the variations in ignition delay time using a hot surface when hydrogen and ammonia are added to each other or to methane, leading to defining two new terms for energy systems, Effectiveness Limit and Useful Limits. They can be utilized in future research to better comprehension the properties of fuels mixtures and study the ignition delay time under various circumstances.

This paper is mainly about the areas of non-Newtonian fluid mechanics which are not investigated or not appropriately and sufficiently investigated. In fact, this should also include emerging areas of research in the field of non-Newtonian fluid mechanics due to new scientific and technological developments and advancements. The purpose of the paper is to highlight and draw the attention to these areas so that researchers (especially the young researchers and newcomers to research such as PhD students) invest their resources and efforts in these areas instead of investing in other areas which are previously investigated and hence they are of less priority from this aspect. Apart from the obvious benefit of "leveling up" in research, the attention to these rather neglected and nonexplored areas of research can be beneficial at the scientific and individual levels since it can lead to breakthroughs and new discoveries in these areas of research by inspecting and assessing their potentials and impacts at the theoretical and practical levels and probing their beneficial applications. We will also provide a brief discussion about the possibility of introducing novel tools and methods in these areas of research (and in non-Newtonian fluid mechanics research in general) as well as highlighting some of the existing limitations of the past and current research in the field of non-Newtonian fluid mechanics (noting that this discussion should help in achieving the ultimate objective of this investigation).

The knowledge of reentry vehicles (RV) §ight characteristics regarding geometrical shape, dimensions, and mechanical properties is essential for precise prediction of their §ight trajectory, impact point, and possible deviations according to simulation uncertainties. The §ight characteristic estimations of existing RV require both body dimensions and mechanical properties of the objects. Due to comparatively simple and reliable methods of specifying the vehicle outer dimensions, e. g., photos and videomaterials, the estimation of mechanical properties is a subject of higher uncertainties. Within this study, a generic medium range ballistic missile (MRBM) RV was examined for several modi¦cations such as center of gravity (CoG) position, weight moment of inertia, and initial reentry §ight states. Combinations of these variables with constant aerodynamic properties for maximal lateral accelerations will be determined. Basing on these, potential evasion maneuver capabilities of the RV will be described.

The findings of this research not only provide valuable insights into industrial oven design but also demonstrate the broader importance of adopting systematic approaches and incorporating numerical analysis techniques to achieve clean energy goals. By leveraging such approaches across various industrial sectors, we can pave the way for a greener future, where energy efficiency, environmental sustainability, and economic growth can harmoniously coexist. In today's rapidly evolving world, where the need for sustainable practices and clean energy solutions is more critical than ever, research plays a pivotal role in driving innovation and addressing environmental challenges. The study presented in this article aligns with this overarching goal by focusing on the optimization of industrial oven design, aiming to achieve energy efficiency and high-quality product outcomes. Efficient oven design and optimization hold significant implications for energy conservation, reducing greenhouse gas emissions, and minimizing environmental footprints. By precisely controlling heat distribution and velocity within industrial ovens, such as the one investigated in this study, resource consumption can be minimized, resulting in reduced energy usage and improved operational efficiency. Moreover, the enhanced uniformity in temperature and airflow distribution ensures optimal product quality, reducing waste and promoting sustainable production practices.  A systematic approach to numerical analysis and validation for industrial oven design and optimization is developed.  Computational fluid dynamics (CFD) and the Taguchi design of experiment methods were employed to determine the influential design variables. The 3D CFD model was then compared with experimental results to validate its accuracy. An experimental oven design was developed based on optimal signal-to-noise (S/N) ratios, and the numerical findings were corroborated through experimental measurements, demonstrating a strong agreement. The proposed approach, encompassing the design, manufacturing, and analysis stages, can be applied to diverse industrial oven designs. Using the Taguchi method, the optimal configuration for the industrial oven was determined with the following parameters: four fans (A), spaced 240 mm apart (B), and positioned at a height of 250 mm (C). This configuration was found to provide the best balance of airflow distribution and heat transfer, ensuring uniform cooking throughout the chamber.

Problem statement. Conventional tools of online communication in global networks for support of scientific and research projects fail to handle specific issues that arise at scientific collaboration of different scientific schools. They cannot be used to bring together the knowledge relating to the same field but generated in various scientific schools, under different paradigms and on different conceptual grounds. Existing software solutions, both synchronous (e.g., Webex or ShowDocument) and asynchronous (Zimbra, Google Docs and others) are efficient only when the users share similar understanding of the context and do not bring their own non-formalized meanings in it. Meanwhile, a tool is needed for scientific cooperation that makes it possible to bring one's own meanings and relate them to the common context.

In CFD studies of respiratory events, accurately calculating droplet travel distance and size reduction due to evaporation is crucial. The precision of these studies relies on qualitative experimental data and robust computational methods for characterizing flow domains and solving flow equations. While mesh studies in CFD of respiratory events exist, specific comparisons between graded tetrahedral and hexahedral meshes are lacking. This article addresses this gap by comparing numerical results from graded non-structured tetrahedral and graded structured hexahedral meshes. It examines respiratory droplet size reduction, position, and evaporation time under 0 and 80% relative humidity. A Grid Convergence Index (GCI) test determined optimal element sizes and distributions for balanced computational efficiency and quality. Both meshes produced accurate results for a wide range of droplet sizes, demanding similar CPU times. For small droplets (d ≤ 50 μm), results were similar regardless of humidity. However, discrepancies emerged for larger droplets (d ≥ 100 μm). While tetrahedral meshes aligned with specific 100 μm droplet studies, hexahedral meshes better reflected broader literature findings, suggesting more precise representation of larger droplet evaporation dynamics. In conclusion, graded hexahedral meshes are recommended for CFD studies involving respiratory droplets of any size, offering more reliable results, particularly in closed spaces.

Procesy przepływu masy w materiale mają wpływ nie tylko na sam materiał ale również na warunki panujące w pomieszczeniach z nim sąsiadujących. Opisany tutaj zostanie model transportu pary wodnej w materiale budowlanym. Po walidacji wprowadzony do niego zostanie model histerezy sorpcji. Ostatecznie zaprezentowane zostanie porównanie wyników symulacji przepływu masy w materiale dla modelu bez i z histerezą.

The hydraulic structures are one of the important constructions needed in open channel flow to control the water level, one of these hydraulic structures is the sluice gate, which is needed for flow diversion as well as a measurement device in the irrigational channel. Many studies that dealt with gate hydraulic properties and energy dissipation downstream gates as a single opening, while the studies dealt with different opening sluice gates still need to be investigated and deep focusing especially on the operating system. In this study, the hydraulic jump efficiency with the different operating systems and different energy dissipaters systems were studied. The higher average percentage of jump efficiency reached 98.76% when intermediate gates were opened, while the lowest value reached 40.36% when side gates were opened. The intermediate height dissipaters as well as nearer to sluice gate gives the highest value of jump efficiency. The baffle block obstacle type gives the best value of jump efficiency compared with other different types.

Este informe técnico presenta un estudio interdisciplinario de diseño y simulación de un reactor de cuasifusión miniaturizado basado en emulsiones de óxido de zinc (ZnO) y óxido de estaño (SnO). Mediante modelado magnetohidrodinámico (MHD) en OpenFOAM, visualización en ParaView y análisis dimensional optimizado, se logró reducir el volumen del reactor a menos de 3 litros con densidades de energía activa superiores a 1400 kW/m³. La cápsula estructurada helicoidalmente y la acción de precesión de láseres permiten estabilizar el autoconfinamiento. El informe incluye visualizaciones tridimensionales, cálculos de bobinas, potencia de ignición, geometría y generación de malla CFD-MHD para simulación de flujos resonantes.

El parangón QHD - MHD debería tener para CHD un argumento base de valores de potencia por metro cúbico como el indicado, partiendo de una velocidad tangencial del agua de 7.5 m/seg.
Luego la comparación invertida para corroborar los supuestos…

Puede ver el conjunto de archivos de datos ejempleficativos en:

https://doi.org/10.5281/zenodo.15132291

Węgiel kamienny zawiera około 60 pierwiastków ślado wych, z których kilkanaście występuje w ilościach znacznie przekraczających klarki litosfery. Budzą one szczególne zainteresowanie geochemików, technologów, a ostatnio także i ekologów. Węgiel bowiem, jako surowiec energetyczny, jest w wysokim stopniu uciążliwy dla środowiska ze względu na emisję produktów spalania, występujących 680 zwłaszcza w fazie stałej i w postaci par, w tym połączeń wielu pierwiastków i radionuklidów silnie toksycznych. Rząd wielkości tej emisji jest funkcją wielu czynników: Zależy on głównie od ilości i jakości spalanego paliwa, a także od fizycznych i chemicznych właściwości pierwiastków. Badania J.M. Pacyny (9) nad zachowaniem się 19 pierwiastków w strumieniu spalin na drodze od paleniska

GEOCHEMICAL AND ECOLOGICAL EVALUATION OF PB-ENRICHED COALS FROM THE CHEŁM DEPOSIT Summary The paper presents results of chemical analyses of 219 coal samples from the Chelm deposit (Lublin Coal Basin). Content of lead in ashes was estimated by the method of atomic absorption spectrometry. Distribution of frequency of lead concentrations shows that the hulk of coals are characterized by low (160 ppm) concentrations of that element as recounted into ash, and the share of coals with increased (600 ppm) and high (1400 ppm) concentrations of lead is relatively low (below 10 %). The analysis of dependence of concentrations of lead in ash on ash content in coal showed that this element is genetically mainly related to inorganic matter (77 %), rather than to the organic (23 %). The results of the studies showed that coals from the Chelm deposits are of minor importance as a hazard for the environment when used as energy raw materials.

The lattice-Boltzmann method is a possible alternative to standard computational fluid dynamics (CFD) or direct simulation Monte Carlo (DSMC) simulations of fluid flows in continuum, slip and transition regimes. We evaluate the accuracy of the lattice-Boltzmann (LB) method for the simulation of microchannel fluid flows at finite Knudsen numbers. A novel modeling of the adaptive Knudsen number as a function of fluid density is proposed in the lattice-Boltzmann model. Specific boundary conditions are used to represent the slippage at the wall and for the simulation of open flows. We compare our simulation results with DSMC data.

The light is one of the important factors for the microalgae growth in the biofuel technology. As biofuel project is large and expensive thus before setting a microalgae based biofuel project in any geographical location, it is important to investigate the suitability of all important parameters involving with the system. This paper aims to investigate the sunlight availability and the microalgae growth for a photobioreactor at Chittagong University of Engineering and Technology (CUET). A computational growth model related to the average irradiance is proposed to calculate the growth of microalgae. We observed that average irradiance is the highest in June and is the lowest in December. From our simulation it is found that the growth of microalgae varies with the average irradiance in a year.

This work involves an experimental study on the performance of automobile airconditioning systems by adding Al 2 O 3 nanoparticles to oil compressors to investigate their impacts on the enhancement of the speed cooling of refrigeration systems and to compare it with the system operated using only oil. The Al 2 O 3 nanoparticles have been added to the oil compressor for different ranges of mass concentration (Ø = 0.1%, Ø = 0.15% and Ø = 0.2%). The stability of Al 2 O 3 nanoparticles has been tested by direct observation for different time periods. The results indicated that the air conditioning system that operated by using Al 2 O 3-oil was better than the system that operated with pure oil. For Ø = 0.2%, the results indicated that the cooling speed and the efficiency of the system operated with Al 2 O 3-oil are increased by 13% and 18%, respectively, as compared to the pure oil system. This study shows that the thermos-physical properties of refrigerant oil are enhanced by 15% when Ø is increased.

The "Life Cycle Assessment" (LCA) is a process to evaluate the environmental burdens associated with a product, process or activity by identifying and quantifying energy and materials used and wastes released to the environment, and to assess the impact of those energy and materials used and releases to the environment. The assessment includes the entire life cycle of the product, process or activity, encompassing: extracting and processing raw materials; manufacturing, transportation and distribution; use, re-use, maintenance; recycling and final disposal. The LCA orients the assessment of environmental impact of a product system to the areas of ecosystem, human health and resources used. In the light of the obligations imposed by the European Union on its member states regarding the minimisation of environmental impact of the fuel industry, the LCA method helps to meet these requirements and is a useful tool to fulfil such obligations. It covers the whole life cycle of a fuel, from the raw material extraction, through the fuel production and use, to the procedures of management of the fuels that do not meet the applicable standard requirements. The life cycle assessment (LCA) method has been described as one of the methods that make it possible to estimate the environmental impact of the process of manufacturing biogas as a fuel intended for internal combustion (IC) engines. Individual stages of the LCA process as well as the assessment preparation principles and requirements are governed by the ISO 14000 series of standards (from 14040 to 14049) and the corresponding Polish equivalents.

Traditional surface water intake structures often face challenges such as cavitation, and vortex formation, reducing efficiency, increasing maintenance costs or even imposing risks for their operations. This study investigates a telescopic water intake, focusing on hydraulic performance, vortex dynamics, and structural optimization. An extensive literature review on vortex formation in surface water intakes identified key equations for critical submergence depth, which were applied in a parametric study of telescopic intake systems. The study examined gas-core vortex formation, a critical factor influencing intake efficiency. Various funnel geometries were analyzed under different submergence depths to assess their impact on vortex behavior. Additionally, the flow rate coefficient's (µ) effect on funnel geometry and vortex development was investigated. A new formulation for gas-core vortex formation was derived to optimize intake design and mitigate performance issues. Computational Fluid Dynamics (CFD) simulations validated the theoretical framework. Numerical simulations detailed velocity distribution, pressure fluctuations, and vortex characteristics. The results of this study were compared with those of previous research dedicated to vortex formation in telescopic water intakes. Unlike prior studies, this research examines four different methods for determining the critical submergence depth to prevent vortex formation and identifies the most effective approach. Results indicate that telescopic intakes can adapt to fluctuating water levels, reducing vortex risks and improving sediment exclusion. Optimized intake geometry, submergence depth criteria, and flow regulation strategies were proposed for enhanced performance. This research contributes to hydraulic engineering by introducing a sustainable water intake solution, addressing vortex-induced limitations and ensuring long-term efficiency in water resource infrastructure.

Este informe técnico presenta un estudio interdisciplinario de diseño y simulación de un reactor de cuasifusión miniaturizado basado en emulsiones de óxido de zinc (ZnO) y óxido de estaño (SnO). Mediante modelado magnetohidrodinámico (MHD) en OpenFOAM, visualización en ParaView y análisis dimensional optimizado, se logró reducir el volumen del reactor a menos de 3 litros con densidades de energía activa superiores a 1400 kW/m³. La cápsula estructurada helicoidalmente y la acción de precesión de láseres permiten estabilizar el autoconfinamiento. El informe incluye visualizaciones tridimensionales, cálculos de bobinas, potencia de ignición, geometría y generación de malla CFD-MHD para simulación de flujos resonantes

The present paper addresses the process of preliminary design of low pressure fan and outlet guide vane (OGV) of a boundary layer ingestion propulsion system. The tail-cone thruster systems of NASA's STARC_ABL adopts axisymmetric BLI type inlet as opposed to other embedded engine systems. Thus, the focus of the present work is placed on maximizing the efficiency of the fan and OGV stages under a significant radial distortion. A parameterization with B-spline function for camber line angles, metal chord, thickness distribution and stacking axis of blades are presented. The flowpath lines are also parameterized by B-spline function and aggregated in the design system of blades. The design optimization with evolutionary algorithm is performed with constraints of fan pressure ratio, OGV exit swirl angle and nozzle exit properties. The inlet conditions for the turbo-machinery CFD domain and the design goal of the fan stage are driven by propulsion airframe integration (PAI) model that uses a 3-D unstructured RANS solver and actuator disk model. The expected power saving of the BLI propulsor is quantified via PAI analysis and the resulting preliminary design of the fan stages is compared with clean inlet flow propulsor.

Droplet motion/departure, which is governed by external force acceleration coefficient, droplet radius and surface wettability on solid surfaces under external forces such as gravitational force, play a significant role in characterizing condensation heat transfer, especially when high fractional non-condensable gases (NCG) present. However, due to the challenge in visualizing the vapor/steam velocity field imposed by droplet motion/departure, the detailed mechanism of droplet motion/departure on condensing surfaces has not been completely investigated experimentally. In this study, droplet motion/departures on solid surfaces under external forces and their interactions with steam flow are simulated using two dimensional (2D) multiphase lattice Boltzmann method (LBM). Large external force acceleration coefficient, droplet radius and contact angle, lead to large droplet deformation and high motion/departure velocity, which significantly shortens the droplet residual time on the solid surface. Our simulation shows that steam vortices (lateral velocity) induced by droplet motion/ departure can greatly disturb the vapor flow and would be intensified by increasing external force acceleration coefficient, droplet radius, and contact angle. In addition, the location of vortex center shifts in the ascending direction with increase of these factors. The average lateral velocities induced by droplet motion/departure at various conditions are obtained. The mass transfer resistance is substantially reduced owing to the droplet motion/departure, leading to an enhanced heat flux. The experimental results are compared to validate the influence of droplet motion/departure on condensation heat transfer performance, especially for steam-air mixture with the presence of high fractional NCG.

In this work, a prototypal ventilated roof for residential use is numerically investigated. The roof is a symmetric structure, both in geometrical and thermal terms, so only a single flap of the roof is studied. Thermofluidodynamics characteristics of the roof are analyzed as a function of geometric parameters: the inclination of the roof, the width of the ventilation layer and the height of the ridge. The model is analyzed as two-dimensional thanks to the commercial code Ansys Fluent. It is evaluated in air flow, considering a k-ε turbulence model to give the governing equations. Results are function of an assigned heat flux on the top wall of the ventilation layer. Results are analyzed thanks to distributions of temperature and air velocity and profiles of wall temperature and air velocity along the cross sections and longitudinal sections of the ventilated layer to consider the different effects of the various geometric configurations. The objective is to study the thermal and fl...

This paper describes the development of a three-dimensional computer code that predicts fluid mechanics, heat and mass transfer and chemical kinetics within a reacting char bed and its application to black liquor. Finite-volume equations estimate pressure drop through porous media with the Ergun equation, a semi-empirical equation based on Darcy's law, to predict fluid flow. Gas and particle temperatures are calculated using established albeit mostly empirical heat transfer correlations together with heat released/absorbed by chemical reactions. The model predicts air flow, including penetration depth into the bed and heat transfer between the bed and the surrounding gases. A companion project collecting experimental information from laboratory and commercial scale beds should provide experimental data for validation in the near future. In the absence of such data, current validation consists only of qualitative analysis of quantitative predictions. This model has not yet been incorporated into a comprehensive computer code, but its use in such codes is illustrated based on previous work coupling simpler bed models with CFD codes.

The article concerns the issue of improving the design and increasing the stability of a telescopic water intake. The design features and operation principles of the existing water intakes are analyzed and their disadvantages are revealed. The article proposes design solutions to improve and increase the stability of the telescopic water intake in the presence of external influences that contribute to the overturning and destruction of the device. In order to increase the stability of the telescopic water intake, a pile structure with a peculiar connection to the water intake float is proposed. A methodology for calculating and designing a telescopic water intake is described and a specific example for its implementation is given.

Telescopic water intake structures have an important role in the water management system. Telescopic water intake has high mobility, wide field of application, at the same time, it is very simple and convenient to operate. But despite these advantages, structural solution for flow energy dissipation in the downstream is lacking, exact calculation method of flow energy dissipating structure is lacking, structural solution to prevent floating objects entering inside the water intake structure is lacking, structural solution to stop water intake operation is lacking. In this regard, the purpose of this research is to improve the design of the existing telescopic water intake, to develop the design and calculation method for the stilling well. Structural solution for flow energy dissipation by means of stilling well is proposed. To protect the water intake from the ingress of floating objects and debris, protective mesh is designed. A shutter is provided to stop water intake operation of the unit. Methodology for analytical hydraulic calculation of a stilling well has been developed. In order to verify above mentioned calculation methodology, analytical calculations and numerical modeling of specific example were performed. Following results of analytical calculation main parameters of stilling well were obtained: length and depth. Results of numerical modeling demonstrated effective energy dissipation in the stilling well and acceptable flow velocity at the entrance to the channel.

Telescopic water intake structures play an important role in a water management system. The article is devoted to the improvement of telescopic water intake structures and the development of a solution for regulating their operation. Different types of water intakes are analyzed, and their shortcomings are identified. The structures of known telescopic water intakes are reviewed, and their operating principles are analyzed. It has been determined that the design of existing telescopic water intake structures lacks a device for stopping the operation of the intake of water. A structural solution for stopping and regulating the operation of a telescopic water intake is proposed. The construction of an additional ballast pontoon to be welded to the first section of the telescopic pipeline is proposed in order to regulate and stop the operation of the water intake. A methodology for calculating and designing an additional ballast pontoon for a telescopic water intake has been developed, and a specific example for its implementation has been provided. Based on the results of the research, the main parameters of the additional ballast pontoon structure have been established, and the methodology for its calculations has been developed.

Telescopic water intake structures allow for the selective intake of water from the top layers of a reservoir. A telescopic water intake has a high degree of mobility, and a wide field of application; at the same time, it is very simple and convenient to operate. Despite these advantages, an exact calculation method for a telescopic water intake is lacking (Lipin, 2020; Lipin, 2022). Therefore, the purpose of this research is to develop an exact calculation method for a telescopic water intake. In order to perform this task, all the structural elements of a telescopic water intake were analyzed separately by means of existing hydraulic principles. The impact of the critical submergence depth of the water intake funnel on the operability of a telescopic water intake was studied, and an equation for the critical submergence depth calculation was proposed. The optimal range of the flow rate coefficient (μ =0.30-0.45) was proposed for calculating the funnel flow rate, and the correlation between the flow rate and funnel inlet diameter was defined. The optimal curvature radius of the elbow was proposed. In order to verify the above mentioned parameters and correlations, analytical and numerical calculations of specific examples were performed. The results of the numerical modelling demonstrated that the critical submergence depth and shape of the water intake funnel, as defined by the analytical calculations, ensured its effective operation free of cavitation and vortexes. The analytically calculated dimensions of the telescopic column, following the numerical modelling results, provided normal hydraulic conditions without active cavitation. According to the numerical modelling, the proposed curvature radius of the elbow was sufficient to avoid significant cavitation and vortex formation in the elbow structure. This research can provide guidance for the design of telescopic water intake structures.

A complete flow control over road vehicles is difficult to achieve because of different phenomena occurring in flow evolution, i.e. the wheel rotation and ground effect deeply influence the flow features. In spite of this, the problem can be approached following different strategies considering both passive and active flow control techniques. The flow around bluff body road vehicle exhibits a massive separation region and as a consequence the drag is mainly due to pressure losses. The total aerodynamic drag of such bodies can be roughly split into three main contributions. The rolling tire account for up to 25-30% whereas the rear part gives rise to 40-45% of the total drag. The remaining is due to the underbody flow and interferences. The wake structure is greatly influenced by the rear geometry of the body that determines the pressure field in this region. As showed by Ahmed [1] and by Iuso [2] the afterbody geometry plays a key role for the drag contributions and also for drag re...

The importance of coastal protection increases with the increase of coastal development. Soft and hard protection measures are the most used techniques. However, hard structures are still preferable. Hard structures are characterized by a long lifetime and high stability in high storms states. Many innovative, environmentally friendly hard coastal protections measured have been proposed and used for specific applications. Breakwaters, for example, are structures designed to sustain and dissipate the energy produced by waves. They help stabilize the coast and preserving ports, beaches, and other coastal resources and habitats. Due to their aesthetic advantages and high structural efficiency, semicircular breakwaters have been used in various locations worldwide. Coastal structures are subjected to hydrodynamic forces usually estimated through physical models and experiments, which is still a realizing tool to study and design such systems. However, these models are difficult to implement, requiring high costs and long experimental procedures. Thus, alternative methodologies for analyzing the hydrodynamic efficiency of these structures are extremely beneficial. The main objective of this research is to develop and check a new coastal structure shape. Corrugated Semi-circular Breakwater (CBW) is proposed. This structure is modified from the Semi-circular Breakwater (SCBW), one of the hard protections used in Japan and China, to increase its efficiency in coastal protection and electricity generation. A comparative study between CBW and SCBW is carried out physically in a two dimensions wide wave flume with dimensions 1.2*1.2*40 m in the Lab. of Coastal Research Institute (CoRI). A computational fluid dynamics tool (Flow-3D) is used to compare the physical models numerically. The numerical model was calibrated and tested using experimental data, considering the effects of water depth and wave characteristics. The study checked the effect of the structure in emerged, low crest, and submerged conditions under different conditions. The reflection, transmission, and dissipation coefficients are used as the efficiency indicators, in addition to changes in current velocity. The results showed that the numerical model accurately simulates wave flume and semi-circular breakwater's interaction with the fluid. Furthermore, CBW has demonstrated its high efficiency in wave dissipation, current velocity reductions, and bed stability than SCBW. CBW shows significant reduction in wave transmission in partially submerged scenario compared to SCBW. It is recommended to use the CBW as a protected structure within the recreational coastal areas. vii ACKNOWLEDGMENT .

Efficient thermal management is a critical challenge in various industries, particularly in electronics cooling, battery thermal management, and renewable energy systems. Phase Change Materials (PCMs) have emerged as an effective passive cooling solution due to their ability to absorb and store heat through latent heat energy. This project aims to evaluate the thermal performance of PCM-based heat sinks with and without fins using Computational Fluid Dynamics (CFD) simulations in ANSYS Fluent. The study compares rectangular and triangular fins to determine their impact on heat dissipation and PCM melting behaviour. The results demonstrate that the inclusion of fins significantly enhances the heat transfer efficiency of the system, with triangular fins exhibiting the best performance due to their increased surface area and improved conduction paths.

The rapid development of Graphics Processing Units (GPU) largely accelerates the application of Large Eddy Simulations (LES) for Gas Turbine Combustion (GTC). Although LES has been implemented into CPU-based CFD solvers for decades, most GTC-LES calculations are still confined to relatively low mesh resolutions and simple physics, in order to avoid very long run-times and hence high computational costs within combustor design cycles. Recently, a newly-developed, native GPU solver built within Ansys Fluent® offers a better option: it allows faster LES on very fine meshes with complex geometries and physics for GTC simulations, significantly reducing the computational time while retaining sufficient solution accuracy. This native GPU solver has been validated across various reacting flow simulations, and good consistency has been achieved between GPU and CPU solutions. In this work, the same GPU solver has been further evaluated on an industrial-based, partially-premixed PRECCINSTA Burner, and the main focus is to analyze the GPU solver's accuracy and speed using appropriate chemical reaction mechanism and chemistry acceleration model. In the current GPU simulations, the LES method with the WALE sub-grid scale model is used for turbulence. The Finite Rate model and the Stiff Chemistry solver are applied for combustion and chemical reactions, respectively. A new reaction mechanism called MFL28, which has 28 species and 159 reaction steps, has been utilized. It matches well the adiabatic flame temperature, laminar flame speed, and ignition delay time of the detailed GRI-3.0 mechanism. Additionally, a chemistry acceleration model called Chemistry Agglomeration (CA), which is newly-implemented into the GPU solver, has been tested to further accelerate the GPU LES simulations. The present work has found that: (1) the GPU solutions with the MFL28 mechanism match the experimental data well on flow velocity, temperature, and CO mass fraction at all measurement locations; (2) the application of the CA model has negligible impact on the GPU results, and can further increase the GPU solver speed and the equivalent number of CPU cores per GPU card by more than three times. These findings give us confidence to extend the current GPU solver with CA acceleration to more complicated gas turbine combustor simulations.

Dedico este trabalho à minha família, especialmente meus queridos pais Elvino e Maria que são a razão da minha existência e me criaram com muito amor e carinho . . . iv AGRADECIMENTOS À Deus, acima de tudo! Aos meus pais, pelos valores que me ensinaram e por sempre acreditarem na minha capacidade. Ao professor e orientador Marcelo Krajnc Alves, mais que um agradecimento, e sim uma homenagem pela orientação acadêmica ímpar e as lições de como enfrentar as grandes adversidades com coragem, determinação e confiança. Obrigada pelos seus preciosos ensinamentos e amizade. Aos queridos primos Carlos e Ruth, pelo carinho, incentivo e apoio. As minhas "grandes" amigas Ana, Cris, Dani e Edi, por todos os momentos de companherismo e descontração. As amigas Cris e Claires, que além de todo apoio contribuíram nas correções ortográficas. Ao amigos e colegas, Bruno, Guilherme, Hilbeth, Miguel e Rodrigo, por me auxiliarem sempre que preciso. À todos os amigos e colegas da UFSC, em especial, André, Anderson, Antônio,

For the model Poisson problem we propose a method combining the discontinuous Galerkin method with a mixed formulation. In the method independent and fully discontinuous basis functions are used both for the scalar unknown and its flux. The continuity requirement is imposed by Nitsche's technique . In the implementation the flux is eliminated by local condensing. We show that the method is stable and optimally convergent for all positive values of the stability parameter. We also perform an a posteriori error analysis. The theoretical results are verified by numerical computations.

Measurements of rise/settling velocity of bubble/particle in SLFB are carried out. Developed a mathematical model to predict slip velocity based on energy balance approach. The predicted values show good agreement with experimental results. PIV measurements show good correspondence with energy balance approach.

One of the classical problems in fluid mechanics is the determination of the flow field around a bluff body represented by a circular cylinder. This is of great interest in many engineering applications, such as hydrodynamic loading on ocean marine piles and offshore platform risers and casing pipes etc. The hydrodynamic behavior of the complex flow field around variety of circular cylinders shall be investigated. Wave induced vibration of structure such as marine pipelines, oil terminals, tanks and ships by placing oscillatory pressure on the surface of the structure. Flow-induced vibrations of slender marine structures can result from external or internal flows. VIV phenomenon is widely seen in subsea applications for risers, conductors, seabed pipelines and other subsea structures. FLIP occurs for rough bore flexible pipes, i.e. pipes with a corrugated metallic inner liner carcass is used for dry gas transport. As dry gas passes through a flexible riser, an unstable shear layer is generated off each of the internal corrugations which make up the internal carcass. Above a certain flow velocity vortices are shed from the carcass, at a frequency resulting in the generation and propagation of acoustic vibrations that lead to fatigue damage to topside and subsea small bore piping. The experimental work is carried to determine the dependence of the exact geometry i.e. corrugation geometry, length of the corrugated tube and the boundary conditions on the generation of pulsations. The obtained analytical tools will be validated by detailed CFD simulations and laboratory experimental tests.

Cilj ovog rada je ispitati racunske neizvjesnosti primjenom razlicitih postupaka analize pouzdanosti brodskog trupa. Za modeliranje granicne cvrstoce brodskog trupa pod zajednickim djelovanjem uzdužnih momenata savijanja na mirnoj vodi i na valovima, kako u progibu tako i u pregibu, preuzete se preporuke Međunarodne organizacije za pomorstvo (IMO) za ocjenu pouzdanosti. Primjer u clanku razmatra tipicnu službu tankera za kemikalije za tek izgrađeni brod i za trup izložen hrđanju. U clanku su uspoređena tri postupka analize pouzdanosti: Metoda prvog reda sa statistickim momentima drugog reda (FOSM), Napredna metoda prvog reda (AFORM) i Monte Carlo simulacija (MCS). U zakljuccima se rezimiraju podaci usporedbi primijenjenih numerickih postupaka za proracun pouzdanosti na elektronickim racunalima te se raspravljaju odgovarajuci postupci za ocjenu sigurnosti brodskog trupa.

Cogenerated heat and power production on a large scale is widely known and is used in industry (industrial
combined heat and power plants), municipal heating systems and public utility buildings (hospitals, office buildings).
However, the application of this technology on a smaller scale is rarely implemented due to high investment costs and
a poorly developed market for such equipment. Significantly lower non-renewable primary energy factor for heat
production in cogeneration systems compared to traditional heating systems (boilers and heating plants), makes it
possible to meet the goals of the Green Deal in terms of increasing building energy efficiency.
The article presents the results of energy efficiency evaluation of 1,1 kW heating capacity and 0,75 kW electrical
power the PEM-type fuel cell powered by natural gas. The operating cycle of the fuel cell is 48 hours: 46 hours of
device operation followed by a 2-hour of technological break for necessary regeneration. Measurements of cooling
water flow and temperatures, natural gas consumption and electricity production allowed for derivation of daily
average energy efficiency and nonrenewable primary energy effort factor of tested the fuel cell. It has been found
that during the study period, the average energy efficiency and a non-renewable primary energy effort factor of the
fuel cell tested have been 82.1% and 0.319 respectively, highlighting the attractiveness of using such a device as the
energy source in single-family residential buildings.

Cryochambers (cryogenic chambers) are devices designed and used for cryotherapy. The treatment involves
exposing the human body to extremely low temperature (below – 100°C) for a short period of time. Cryochambers
have been designed and manufactured for over 35 years in Poland. They have usually been used in hospitals and
rehabilitation centres. Recently, low-temperature sessions have been lately recognised as an effective method of
regeneration and wellness. Therefore, they are becoming available in gyms and beauty centres. Achieving such low
temperatures requires the use of gases with properties that may pose a potential risk to cryochamber users. This article
presents methods of achieving cryotherapy temperatures, describes the properties of working fluids, safety analysis
and risk assessment of cryochamber operation. Special attention has been paid to the cryochambers supplied with
liquid nitrogen.

The widely-used Blade Element Momentum theory is inadequate for aeroelastic analysis of wind turbines. It is the purpose of this study to develop a program in which Non-linear Numerical Lifting Line method is implemented, so as to conduct aeroelastic analysis, i.e. take the deformation turbine blades incur under wind load into account. This paper includes the explanation and some test applications of the mentioned method.

Envi-met is the most-used simulation tool to assess outdoor thermal comfort in urban microclimates. Considering reported disparities between modeled and observed mean radiant temperature (MRT), failing to accurately predict the MRT may have a negative impact on the conclusions drawn by urban designers and policy makers. Therefore, this study aims to validate the Envi-met model's efficiency for predicting MRT in the hot arid climate of Mecca city. Sensitivity analyses were conducted to investigate the settings and inputs of Envi-met, including two-and six-directional methods for calculating MRT, shortwave radiation projection factors, Indexed View Sphere (IVS), Advanced Canopy Radiation Transfer (ACRT), and the localization of materials and vegetation. Two statistical metrics (RMSE and MAE) were employed to assess Envi-met's performance for the two evaluation points. Envi-met produced the best results with the 6-directional, ƒp-RayM (in winter) and ƒp-City (in summer), IVS on and ACRT on mode, and localized soil condition, materials, and vegetation inputs. An analysis of the modeled MRT results illustrated that error magnitudes were decreased significantly as a result of sufficient settings and inputs; for example, RMSE was improved by 2.31 and 8.48 K in the winter and summer open site results, respectively, and by 7.30 K in the summer under-tree site. Overall, the results of winter and summer analyses demonstrate average RMSE of 4.99 K and MAE of 4.02 K. The findings illustrate that substantial enhancement of model performance can be achieved through the use of proper settings and inputs.

At Analyzer, we understand that precision and safety are non-negotiable in the nuclear ecosystem. Finite Element Analysis (FEA) serves as a cornerstone for ensuring the structural integrity and performance of critical components in nuclear power systems. From reactor cores to containment vessels, FEA allows us to simulate and analyse material behaviour under extreme conditions, including high temperatures, pressure loads, and seismic forces. Our expertise in FEA helps identify potential vulnerabilities, optimize designs, and ensure compliance with stringent industry regulations. By leveraging cutting-edge simulation tools, Analyzer enables engineers to mitigate risks and enhance the reliability of vital infrastructure, ensuring safe and efficient operation throughout the lifecycle of nuclear facilities.

Small hydropower (SHP) is a renewable, efficient and eco friendly technology. Out of all the essential civil components, the desilting tank is one of the most vital part of SHP schemes, which ejects the sediment and foreign particles carried by water through the conductor system and protects the hydro mechanical equipments. With the passage of time, the desilting device has undergone modifications and updation as per the choice of developer or the geological condition and economic constrains. In this paper, attempt has been made to review the different types of desilting devices being deployed in SHP plants in the Himalayan region.

The convergent-divergent design of the nozzle of a rocket engine is the most defining part of it. The nature of the nozzle design enables it to convert the high pressure, temperature and relatively low velocity adiabatic expanding gaseous fluids into very high velocity and thrust gases. The rapidly exiting gas as a consequence of the rapid expansion process results in low pressure and temperature. It is critical in research to find out the influence of modification (grooves) would have in the application and design of a reaction device such as a rocket engine. The Computational Fluid Dynamics software, Analysis System (ANSYS) was employed together with necessary boundary conditions to design and simulate such a modified rocket engine nozzle. The interaction and relationship existing among the pressure, velocity, Mach number and temperature in the grooved divergent rocket nozzle was found and observed. From the plots and nozzle simulation contours, both velocity and Mach number increased rapidly along the nozzle area but decreased steadily. Pressure varied directly withtemperature and inversely with density. It is observed that divergent nozzle grooving influences the velocity, Mach number, pressure and temperature within the divergent nozzle area of a rocket nozzle.

Images In this work we present an automatic algorithm for detection of mycobacterium tuberculosis from stained sputum smear images applying a novel method of tubeness filtering in conjunction with Otsu thresholding and connected component analysis. This eliminates human effort and measurement error from the detection of the bacteria, which normally requires a lab technician or pathologist to load a glass slide with a patient’s stained sputum smear into a digital fluorescent microscope and visually search for mycobacterium tuberculosis in several different fields of view. On the other hand, the proposed automated detection of mycobacterium tuberculosis from stained sputum smear digital images renders fast analysis of patient’s sputum for quick and efficient diagnosis of tuberculosis.