wyświetlamy 1000 najlepszych wyników Pomoc
Wyniki wyszukiwania dla: forced vibrations, inertial exciters, multibody dynamics, numerical analysis
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BADANIA ODBIOROWE ŁUKOWEJ KŁADKI DLA PIESZYCH 10T NAD DROGĄ S8 W WARSZAWIE
PublikacjaThe paper presents in situ load testing of the newly build footbridge over S8 expressway in Warsaw. The most characteristic thing for the structure is a shape of arch girders, which correspond with adjacent half-tunnel acoustic baffles. The paper consists of description of the structure, results of the in-situ static and dynamic load testing, results of the numerical simulations, comparative analysis and final conclusions on the...
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Modal FEM Analysis of Ferrite Resonant Structures
PublikacjaThe finite-element method (FEM) is applied for modal analysis of ferrite-loaded spherical resonators. To improve the efficiency of the numerical calculations, the body-of-revolution (BOR) technique is utilized. Due to the frequency-dependent ferrite permeability, FEM leads to a nonlinear eigenvalue problem that is challenging to solve. To this end, Beyn’s method is proposed. The effectiveness of the proposed approach is confirmed...
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Research on protection mechanisms of Resilient Packet Ring Network.
PublikacjaPaper describes iSteering - a new method to control traffic in case of RPR network failure. There's comparison of packet wrapping, steering and our proposed method iSteering, which can be used in case of transmitter/receiver or fiber failure. Numerical analysis for even and random traffic flow has been made in order to compare packet wrapping, steering and iSteering. The results of all the tests are included.
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Concept of an Innovative System for Dimensioning and Predicting Changes in the Coastal Zone Topography Using UAVs and USVs (4DBatMap System)
PublikacjaThis publication is aimed at developing a concept of an innovative system for dimensioning and predicting changes in the coastal zone topography using Unmanned Aerial Vehicles (UAVs) and Unmanned Surface Vehicles (USVs). The 4DBatMap system will consist of four components: 1. Measurement data acquisition module. Bathymetric and photogrammetric measurements will be carried out with a specific frequency in the coastal zone using...
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„Eulerian – Eulerian” versus ,,Eulerian –Lagrangean” models of condensation
PublikacjaLiquid phase in the flowing vapor through stages of the steam turbine is the cause of a lot of failures. Nowadays, due to work of steam turbines at partial load, process of homogeneous and heterogeneous condensation still is current. The formation of drops of condensate under conditions other than nominal operation of turbine is a process still unknown. Engineers and designers involved in the development of power station machines...
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Four Degree-of-Freedom Hydrodynamic Maneuvering Model of a Small Azipod-Actuated Ship With Application to Onboard Decision Support Systems
PublikacjaThe main contribution of this paper is a numerical ship motion model of NTNU’s research vessel Gunnerus, capturing the surge, sway, roll, and yaw dynamics when sailing in uniform and steady currents. The model utilizes a crossflow drag formulation for the transverse viscous loads, and it includes a nonlinear formulation for the propulsion and steering loads provided by two azipod thrusters. A wide range of experimental data obtained...
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Numerical investigation of multiphase blood flow coupled with lumped parameter model of outflow
PublikacjaPurpose The purpose of this paper is the application of the computational fluid dynamics model simulating the blood flow within the aorta of an eight-year-old patient with Coarctation of Aorta. Design/methodology/approach The numerical model, based on commercial code ANSYS Fluent, was built using the multifluid Euler–Euler approach with the interaction between the phases described by the kinetic theory of granular flow (KTGF). Findings A...
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Old Problems - New Solutions: Conversion of Capitals as a Tool for Shaping the Competitive Position in the Economic Field
PublikacjaThe acts and operations any social actor effectuates in each of the logically distinguished spheres of reality are conditioned by many factors, among which a reliable analysis of the strengths and weaknesses of an agent should be considered of utmost importance. The concept of capitals presented in this article divides the quantity of resources available to all acting agents into four main categories (which allows for determining...
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Old Problems - New Solutions: Conversion of Capitals as a Tool for Shaping the Competitive Position in the Economic Field
PublikacjaThe acts and operations any social actor effectuates in each of the logically distinguished spheres of reality are conditioned by many factors, among which a reliable analysis of the strengths and weaknesses of an agent should be considered of utmost importance. The concept of capitals presented in this article divides the quantity of resources available to all acting agents into four main categories (which allows for determining...
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Instantaneous Impedance Analysis of Non-Stationary Corrosion Process: a Case Study of Carbon Steel in 1M HCl
PublikacjaThe paper concerns the problem of evaluation of stationarity of carbon steel corrosion in 1M HCl. Comparison of corrosion rate with addition of corrosion inhibitor to the reference measurement is the most often used way of evaluating inhibitor efficiency. Such an approach is valid only if corrosion rate is a stationary process. Two complementary techniques were used simultaneously: volumetric analysis of evolved hydrogen and instantaneous...
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Combined Single Neuron Unit Activity and Local Field Potential Oscillations in a Human Visual Recognition Memory Task
PublikacjaGOAL: Activities of neuronal networks range from action potential firing of individual neurons, coordinated oscillations of local neuronal assemblies, and distributed neural populations. Here, we describe recordings using hybrid electrodes, containing both micro- and clinical macroelectrodes, to simultaneously sample both large-scale network oscillations and single neuron spiking activity in the medial temporal lobe structures...
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Statistical Method for Analysis of Interactions Between Chosen Protein and Chondroitin Sulfate in an Aqueous Environment
PublikacjaWe present the statistical method to study the interaction between a chosen protein and another molecule (e.g., both being components of lubricin found in synovial fluid) in a water environment. The research is performed on the example of univariate time series of chosen features of the dynamics of mucin, which interact with chondroitin sulfate (4 and 6) in four different saline solutions. Our statistical approach is based on recurrence...
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Modal analysis of a steel grandstand
PublikacjaAmong the issues related to the idea of sustainable society is the safety of civil engineering structures devoted to satisfy different needs of people. One of the types of structures devoted to satisfy recreational needs are grandstands, which are used during sport events or music concerts. It is obligatory to consider interaction between structure and crowd load especially when the crowd movement involves rhythmic jumping, dancing,...
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Damage Imaging in Lamb Wave-Based Inspection of Adhesive Joints
PublikacjaAdhesive bonding has become increasingly important in many industries. Non-destructive inspection of adhesive joints is essential for the condition assessment and maintenance of a structure containing such joints. The aim of this paper was the experimental investigation of the damage identification of a single lap adhesive joint of metal plate-like structures. Nine joints with different defects in the form of partial debonding...
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Modelling of acoustic backscattering by southern Baltic herring
PublikacjaAssessment of Baltic herring abundance can be carried out using acoustic techniques. Analysis of the relationship between the Baltic herring individual target strength, TS, and the total fish length, L, important for the acoustic assessment, showed the relationship to be dependent on the location of the study area. This finding motivated a detailed analysis of the relationship for the herring occurring in the southern Baltic...
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SHORT REVIEW AND 3-D FEM ANALYSIS OF BASIC TYPES OF FOUNDATION FOR OFFSHORE WIND TURBINES
PublikacjaSome problems of the foundations of offshore wind turbines are considered in this paper. A short review is presented on the two basic types of foundations, i.e. monopiles and gravity foundations, including their basic features and applications as well as general design considerations. Also, some issues regarding analysis are discussed, including geotechnical problems and modelling techniques. A numerical model of offshores turbine...
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Role of quantitative chest perfusion computed tomography in detecting diabetic pulmonary microangiopathy
PublikacjaAims: Aimof the study was to determine the role of perfusion chest computed tomography(pCT) in evaluation of pulmonary diabetic angiopathy.Methods: 18 never-smoking patients (10 diabetic patients and 8 healthy controls) underwentchest high resolution CT (HRCT) and then pCT scanning. In both groups, blood tests,biochemical analysis, fibrinogen, HbA1c, spirometry, diffusion capacity for carbonmonoxide(DLCO) and body pletysmography...
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Numerical simulations of novel GFRP sandwich footbridge
PublikacjaIn the following paper some aspects of numerical analysis and designing stages of a footbridge made of composite materials are elucidated. Because of the used materials the design process in this case is not ordinary and requires the development of concepts, material selections, identification of material properties, numerical simulations, strength calculations, serviceability and durability analyses. This contribution presents...
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Viscoplastic damage analysis of structures subjected to impact loading. Plate and shell structures. - Ł. Pyrzowski.
PublikacjaThe work presents the investigation in the response of plate-shell structures subjected to impact loading (gas mixture explosions). This phenomenon is studied in the context of its mechanical aspects, mainly the ductile fracture prediction. The work starts with the literature review and the description of theories, which are nowadays the most popular in the damage and failure modelling. After selecting the theoretical models and...
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Remarks on steam condensation modeling related to steam turbine large output
PublikacjaIn the paper numerical simulations have been performed to predict the performance of the diferent steam models. All of the considered models of steam condensation have been validated on the base of benchmark experiment employing expansion in nozzle and next on the low pressure part of the steam turbine equipped with the so-called Baumann stage. For numerical analysis three models have been finally used - the ideal steam model without...
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Probabilistic sensitivity of limit states of structures : The Monte Carlo simulation
PublikacjaThe main issue of the paper is the probabilistic sensitivity of the limit states of structures with respect to selected input design variables. Attempt to the problem is done by the dedicated Monte Carlo simulation procedure. Basic design variables are random variables of given probability distributions, presented in the form of random numbers. Uni-parametrical increment of the dominant basic variable (basic variables) is done,...
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Response of high voltage disconnector under seismic excitation - experimental and numerical study
PublikacjaThe efficiency of the energetic infrastructure system is a very import safety issue in the region experienced by the ground motion. The aim of the present paper is to show the results of the experimental and numerical study focused on the earthquake-induced response of the high voltage disconnector, which is an important element of energetic network. First, the impact tests as well as the sweep-sine shaking table tests were conducted....
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Turbulence models impact on the flow and thermal analyses of jet impingement
PublikacjaAccurate numerical reconstruction of heat and mass transfer processes in particular applications, such a jet impingement, is difficult to obtain even with the use of modern computational methods. In the proposed paper, the flow and thermal phenomena occurring during single minijet impingement on the flat, concave and convex, heated surfaces were considered. Problem of impingement on non-flat surface, still not common and purely...
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Modeling and control of a redundantly actuated variable mass 3RRR planar manipulator controlled by a model-based feedforward and a model-based-proportional-derivative feedforward–feedback controller
PublikacjaIn the paper, dynamics of a complex mechatronics system is considered. A redundantly actuated planar manipulator is the base of the mechanical part of it. It is a 3RRR 1 platform based parallel manipulator. To control its trajectory, a model-based feedforward controller is employed. Three aspects are fundamental in the presented investigations. The first focus is on development of an accurate numerical model used to solve the inverse...
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Mathematical approach to design 3D scaffolds for the 3D printable bone implant
PublikacjaThis work demonstrates that an artificial scaffold structure can be designed to exhibit mechanical properties close to the ones of real bone tissue, thus highly reducing the stress-shielding phenomenon. In this study the scan of lumbar vertebra fragment was reproduced to create a numerical 3D model (this model was called the reference bone sample). New nine 3D scaffold samples were designed and their numerical models were created....
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Influence of grain shape on the mechanical behaviour of granular materials
PublikacjaWe performed series of numerical vertical compression tests on assemblies of 2D granular material using a Discrete Element code and studied the results in regard to the grain shape. The samples consist of 5000 grains made either of 3 overlapping discs (clump - grain with concavities) or of six-edged polygons (convex grain). These two types of grains have a similar external envelope, ruled with a geometrical parameter α. In the...
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Monte Carlo simulations of the fracture resistance degradation of asphalt concrete subjected to environmental factors
PublikacjaThe paper presents the results of laboratory tests of SCB (semi-circular beam) samples of asphalt concrete, subjected to the destructive effect of water and frost as well as the aging processes. The determined values of material parameters show significant dispersions, which makes the design of mixtures difficult. Statistical analysis of the test results supplemented by computer simulations made with the use of the proprietary...
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Thermal and Hydrodynamic Phenomena in the Stagnation Zone — Impact of the Inlet Turbulence Characteristics on the Numerical Analyses
PublikacjaOne of the methods of heat transfer enhancement is utilization of the turbulent impinging jets, which were recently applied, for example, in the heat exchangers. Their positive impact on the heat transfer performance was proven, but many questions related to the origin of this impact are still unanswered. In general, the wall-jet interaction and the near-wall turbulence are supposed to be its main reason, but their accurate numerical...
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Methods of measurement signal acquisition from the rotational flow meter for frequency analysis
PublikacjaOne of the simplest and commonly used instruments for measuring the flow of homogeneous substances is the rotational flow meter. The main part of such a device is a rotor (vane or screw) rotating at a speed which is the function of the fluid or gas flow rate. A pulse signal with a frequency proportional to the speed of the rotor is obtained at the sensor output. For measurements in dynamic conditions, a variable interval between...
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Changes of Conformation in Albumin with Temperature by Molecular Dynamics Simulations
PublikacjaThis work presents the analysis of the conformation of albumin in the temperature range of 300K – 312K, i.e., in the physiological range. Using molecular dynamics simulations, we calculate values of the backbone and dihedral angles for this molecule. We analyze the global dynamic properties of albumin treated as a chain. In this range of temperature, we study parameters of the molecule and the conformational entropy derived from...
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Nośność konstrukcji gruntowo-łukowej prefabrykowanego wiaduktu w świetle obliczeń numerycznych i badań „in situ”
PublikacjaWartykule przedstawiono analizy przeprowadzone dla wiaduktu WK-15 Pomorskiej Kolei Metropolitalnej wykonanego w technologii łuków prefabrykowanych przykrytych gruntem (system TechSpan). W celu weryfikacji obliczeń numerycznych wykonano próbne obciążenie konstrukcji. Przedstawiono wyniki pomiarów naprężeń i prezmieszczeń konstrukcji. Odniesiono się krytycznie do zastosowanego modelu obliczeniowego.
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Incorporating installation effects into the probability analysis of controlled modulus columns
PublikacjaThis technical report presents the probabilistic analysis which integrates the Monte Carlo simulation (MCS) with random field theory to model the load–displacement behavior of Controlled Modulus Columns (CMCs) in overconsolidated Poznań clay. Presented study focuses on the practical aspects of statistical analysis of geotechnical data, numerical model development, and results evaluation. Variability and spatial distribution of...
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Rapid surrogate-assisted statistical analysis of compact microstrip couplers
PublikacjaIn this paper, a technique for low-cost statistical analysis and yield estimation of compact microwave couplers has been presented. The analysis is executed at the level of a fast surrogate model representing selected characteristic points of the coupler response that are critical to determine satisfaction/violation of the prescribed design specifications. Because of less nonlinear dependence of the characteristic points on geometry...
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INVESTIGATIONS OF THE EMISSION CHARACTERISTICS OF A DUAL-FUEL GAS TURBINE COMBUSTION CHAMBER OPERATING SIMULTANEOUSLY ON LIQUID AND GASEOUS FUELS
PublikacjaT his study is dedicated to investigations of the working process in a dual-fuel low-emission combustion chamber for a floating vessel’s gas turbine. As the object of the research, a low-emission gas turbine combustion chamber with partial premixing of fuel and air inside the outer and inner radial-axial swirls was chosen. The method of the research is based on the numerical solution of the system of differential...
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Wybrane aspekty modelowania matematycznego kolejowego odbieraka prądu
PublikacjaNieprawidłowa współpraca odbieraka z siecią jezdną, w niekorzystnych warunkach lokalnych, prowadzi do uszkodzeń sieci lub odbieraka. Może być to spowodowane niewłaściwym wykonaniem lub utrzymaniem tych istotnych elementów układu zasilania. Tego typu sytuacje awaryjne powodują duże opóźnienia w ruchu pociągów i generują olbrzymie koszty. Wskazuje to na duże znaczenie odpowiednich rozwiązań konstrukcyjnych sieci i odbieraków oraz...
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Badania eksperymentalne i numeryczne zachowania się zbiorników stalowych poddanych wstrząsom górniczym i sejsmicznym
PublikacjaW niniejszej dysertacji opisano wyniki kompleksowych badań zachowania się zbiorników stalowych poddanych wstrząsom górniczym i umiarkowanym trzęsieniom ziemi. Badania prowadzono dla dwóch zbiorników rzeczywistych zlokalizowanych na terenie Polski. W pierwszym etapie badań przeprowadzono badania eksperymentalne na specjalnym stanowisku laboratoryjnym dla modeli doświadczalnych zbiorników. Badania prowadzono dla różnego poziomu wypełnienia...
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Hybrid technique for the analysis of circular waveguide junctions loaded with ferrite posts
PublikacjaThis study presents a hybrid technique for the analysis of circular waveguide junctions loaded with axially symmetrical ferrite posts of irregular shape. The method is based on a combination of the finite-difference frequency- domain technique with a mode-matching technique. The proposed approach is validated by comparing the presented results with numerical ones obtained from commercial software. The application of a cylindrical...
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Prediction of Weld Deformations by Numerical Methods - Review
PublikacjaThe welding process is the basic technique of joining in the shipbuilding industry. This method generates welding distortions that cause a lot of problems during the manufacturing process due to both the time and cost of straightening as well as their influence on later stages of production. Proper preparation of welding processes plays a growing role in the shipbuilding industry and the development of calculating tools is being...
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Conley-Morse graphs for a two-patch vaccination model
Dane BadawczeThis dataset contains selected results of rigorous numerical computations described in Section 5 of the paper "Rich bifurcation structure in a two-patch vaccination model" by D.H. Knipl, P. Pilarczyk, G. Röst, published in SIAM Journal on Applied Dynamical Systems (SIADS), Vol. 14, No. 2 (2015), pp. 980–1017, doi: 10.1137/140993934.
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ADAPTIVE METHOD FOR THE SOLUTION OF 1D AND 2D ADVECTION-DIFFUSION EQUATIONS USED IN ENVIRONMENTAL ENGINEERING
PublikacjaThe paper concerns the numerical solution of one-dimensional (1D) and two-dimensional (2D) advection-diffusion equations. For the numerical solution of the 1D advection-diffusion equation a method, originally proposed for solution of the 1D pure advection equation, has been developed. A modified equation analysis carried out for the proposed method allowed increasing of the resulting solution accuracy and consequently, to reduce...
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Awaria ściany szczelinowej stanowiącej obudowę wykopu głębokiego
PublikacjaW artykule przedstawiono awarię ściany szczelinowej stanowiącej obudowę wykopu głębokiego. Omówiono warunki geologiczne, hydrogeologiczne i geotechniczne podłoża. Przeprowadzono analizę rozwiązań konstrukcyjnych w kolejnych oszczędnościowych modyfikacjach projektu oraz zrealizowanej wersji. Wykonano obliczenia porównawcze. Wskazano przyczyny wystąpienia awarii. In the paper a failure of diaphragm wall protecting deep excavation...
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Impact of an unsecured excavation on an underground pipeline
PublikacjaThe paper presents a numerical analysis of the impact of an unsecured excavation on an underground pipeline in selected soil conditions. The research was inspired by a real-life failure of a water pipeline which was caused by a nearby unsecured excavation (Sikora et al. 2015). The failure was triggered by displacement of soil mass in the vicinity of the pipeline. The study conducted in the framework of Finite Element...
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Estimating the uncertainty of the liquid mass flow using the orifice plate
PublikacjaThe article presents estimation of measurement uncertainty of a liquid mass flow using the orifice plate. This subject is essential because of the widespread use of this type of flow meters, which renders not only the quantitative estimation but also qualitative results of this type so those measurements are important. To achieve this goal, the authors of the paper propose to use the theory of uncertainty. The article shows the...
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Asynchronous Charge Carrier Injection in Perovskite Light-Emitting Transistors
PublikacjaUnbalanced mobility and injection of charge carriers in metal-halide perovskite light-emitting devices pose severe limitations to the efficiency and response time of the electroluminescence. Modulation of gate bias in methylammonium lead iodide light-emitting transistors has proven effective in increasing the brightness of light emission up to MHz frequencies. In this work, a new approach is developed to improve charge carrier...
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Optimization of parallel implementation of UNRES package for coarse‐grained simulations to treat large proteins
PublikacjaWe report major algorithmic improvements of the UNRES package for physics-based coarse-grained simulations of proteins. These include (i) introduction of interaction lists to optimize computations, (ii) transforming the inertia matrix to a pentadiagonal form to reduce computing and memory requirements, (iii) removing explicit angles and dihedral angles from energy expressions and recoding the most time-consuming energy/force terms...
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Local Nusselt number evaluation in the case of jet impingement
PublikacjaJet impingement still is one of demanding cases regarding computational fluid dynamics, due to its highly turbulent behaviour, with occurrence of turbulent-laminar transition. Even recently developed methods exhibit some drawbacks – RANS based simulations lack accuracy, LES and DNS based ones require too much computational time. Hybrid methods also exist, but their development and validation is in progress. Nevertheless, CFD application...
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ANALIZA CECH HYDRO-AERODYNAMICZNYCH BEZZAŁOGOWEGO POJAZDU NAWODNO-POWIETRZNEGO Z WYKORZYSTANIEM EFEKTU PRZYPOWIERZCHNIOWEGO
PublikacjaW artykule przedstawiono problematykę badań dotyczących opracowania demonstratora technologii bezzałogowego pojazdu nawodno-powietrznego z wykorzystaniem efektu przypowierzchniowego. Opisano podstawowe problemy badawcze związane z analizą cech hydro-aerodynamicznych pojazdu. Opisano przedmiot badań, bezzałogowy pojazd nawodno-powietrzny typu USV-UAV-WIG. Opisano metodę badań. Przeprowadzono wstępną analizę osiągów i zachowania...
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Modeling of Passive and Forced Convection Heat Transfer in Channels with Rib Turbulators
PublikacjaThe main goal of the research presented in this paper was the experimental and numerical analysis of heat enhancement and aerodynamic phenomena during air flow in a channel equipped with flow turbulators in the form of properly configured ribs. The use of ribs intensifies the heat transfer and at the same time increases not only the flow resistance but also the energy costs. Therefore, designing modern heat exchangers with optimal...
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A review on analytical models of brushless permanent magnet machines
PublikacjaThis study provides an in-depth investigation of the use of analytical and numerical methods in analyzing electrical machines. Although numerical models such as the finite-element method (FEM) can handle complex geometries and saturation effects, they have significant computational burdens, are time-consuming, and are inflexible when it comes to changing machine geometries or input values. Analytical models based on magnetic equivalent...
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Discrete element method modelling of elastic wave propagation in a meso-scale model of concrete
PublikacjaThis paper deals with the accurate modelling of ultrasonic wave propagation in concrete at the mesoscopic level. This was achieved through the development of a discrete element method (DEM) model capable of simulating elastic wave signals comparable to those measured experimentally. The main objective of the work was to propose a novel methodology for constructing a meso-scale model of concrete dedicated to the analysis of elastic...