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    Wyświetlanie 1-8 z 8
    Tytuł:
    Pyramidal ceramic armor ability to defeat projectile threat by changing its trajectory
    Autorzy:
    Stanislawek, S.
    Morka, A.
    Niezgoda, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/202070.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    computational mechanics
    ballistic protection
    composite armor
    ceramics
    mechanika obliczeniowa
    ochrona balistyczna
    kompozytowy pancerz
    ceramika
    Opis:
    This paper presents a numerical study of a multilayer composite panel impacted by an AP (Armor Piercing) 14.5×114 mm B32 projectile. The composite consists of alternating layers of hard ceramic and a ductile aluminum alloy. While the alloy layer consists of typical plate, ceramics confront projectiles in the form of ceramic pyramids. The studied models are compared with a reference structure, which is a standard double layer panel. The problem has been solved with the usage of modeling and simulation methods as well as a finite elements method implemented in LS-DYNA software. Space discretization for each option was built with three dimensional elements ensuring satisfying accuracy of the calculations. For material behavior simulation, specific models including the influence of the strain rate and temperature changes were considered. A steel projectile and aluminum plate material were described by the Johnson-Cook model and a ceramic target by the Johnson-Holmquist model. The obtained results indicate that examined structures can be utilized as a lightweight ballistic armor in certain conditions. However, panels consisting of sets of ceramic prisms are a little easier to penetrate. Despite this fact, a ceramic layer is much less susceptible to overall destruction, making it more applicable for the armor usage. What is most important in this study is that significant projectile trajectory deviation is detected, depending on the impact point. Such an effect may be utilized in solutions, where a target is situated relatively far from an armor.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2015, 63, 4; 843-849
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigations on an influence of the material properties on vibrations of active rocker-bogie suspension
    Autorzy:
    Sokół, Krzysztof
    Pierzgalski, Maciej
    Powiązania:
    https://bibliotekanauki.pl/articles/2173528.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    frequency analysis
    suspension
    rover
    mobile platform
    computational mechanics
    analiza częstotliwości
    zawieszenie
    łazik
    platforma mobilna
    mechanika obliczeniowa
    Opis:
    Unmanned vehicles are often used in everyday life, mostly by rescue teams or scientists exploring new terrains. In those constructions, the suspension has constant dimensions, which leads to many disadvantages and limits the application area. The solution to these problems can be creating a six-wheeled mobile platform that can dynamically change the wheelbase in relation to the area of action or terrain inclination angle. The active change in location of the center of gravity gives a possibility to access sloppy obstacles not available with classical suspensions. The main scope of this study is to investigate the influence of material properties on vibration frequency at different lengths of suspension members. The obtained results will allow finding the optimum material for producing a prototype unit.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2022, 70, 1; e138239, 1--7
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance comparison of the optimized inverted joined wing airplane concept and classical configuration airplanes
    Porównanie osiągów zoptymalizowanego samolotu w odwróconym układzie skrzydeł połączonych z samolotami o klasycznej konfiguracji
    Autorzy:
    Sieradzki, A.
    Dziubiński, A.
    Galiński, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/139820.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    joined wing
    performance
    computational fluid dynamics
    CFD
    układ skrzydeł połączonych
    osiągi
    obliczeniowa mechanika płynów
    Opis:
    The joined wing concept is an unconventional airplane configuration, known since the mid-twenties of the last century. It has several possible advantages, like reduction of the induced drag and weight due to the closed wing concept. The inverted joined wing variant is its rarely considered version, with the front wing being situated above the aft wing. The following paper presents a performance prediction of the recently optimized configuration of this airplane. Flight characteristics obtained numerically were compared with the performance of two classical configuration airplanes of similar category. Their computational fluid dynamics (CFD) models were created basing on available documentation, photographs and some inverse engineering methods. The analysis included simulations performed for a scale of 3-meter wingspan inverted joined wing demonstrator and also for real-scale manned airplanes. Therefore, the results of CFD calculations allowed us to assess the competitiveness of the presented concept, as compared to the most technologically advanced airplanes designed and manufactured to date. At the end of the paper, the areas where the inverted joined wing is better than conventional airplane were predicted and new research possibilities were described.
    Układ skrzydeł połączonych jest niekonwencjonalną konfiguracją samolotu, znaną od lat 20. ubiegłego stulecia. Cechuje go kilka istotnych zalet, takich jak redukcja oporu indukowanego oraz masy samolotu, ze względu na koncepcję zamkniętego skrzydła. Samolot w odwróconym układzie skrzydeł połączonych jest rzadko rozpatrywanym wariantem tej konfiguracji, z przednim skrzydłem usytuowanym nad skrzydłem tylnym. Niniejszy artykuł przedstawia oszacowanie osiągów zoptymalizowanej wersji tego typu samolotu. Charakterystyki aerodynamiczne, uzyskane na drodze obliczeń numerycznych CFD (Computational Fluid Dynamics – obliczeniowa mechanika płynów), zostały porównane z osiągami dwóch samolotów zbliżonej kategorii o układzie klasycznym. Ich modele obliczeniowe zostały stworzone bazując na dostępnej dokumentacji, zdjęciach oraz metodach projektowania odwrotnego. Analiza obejmowała symulacje wykonane dla skali bezzałogowego demonstratora o rozpiętości skrzydeł 3 m oraz pełnowymiarowej skali, odpowiadającej załogowym samolotom. Tym sposobem, wyniki obliczeń CFD pozwoliły ocenić konkurencyjność zaprezentowanej koncepcji, w porównaniu do najbardziej zaawansowanych technologicznie, obecnie projektowanych i budowanych, samolotów. Na końcu artykułu wskazano obszary, w których odwrócony układ skrzydeł połączonych charakteryzują potencjalnie lepsze osiągi niż układ konwencjonalny i zaproponowano dalszy możliwy kierunek prac.
    Źródło:
    Archive of Mechanical Engineering; 2016, LXIII, 3; 455-470
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    CFD simulation of DEBORA boiling experiments
    Autorzy:
    Rzehak, R.
    Krepper, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/240154.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    obliczeniowa mechanika płynów
    przechłodzenie
    symulacja
    computational fluid dynamics simulation
    heat flux partitioning
    subcooled flow boiling
    two-fluid model
    Opis:
    In this work we investigate the present capabilities of computational fluid dynamics for wall boiling. The computational model used combines the Euler/Euler two-phase flow description with heat flux partitioning. This kind of modeling was previously applied to boiling water under high pressure conditions relevant to nuclear power systems. Similar conditions in terms of the relevant non-dimensional numbers have been realized in the DEBORA tests using dichlorodifluoromethane (R12) as the working fluid. This facilitated measurements of radial profiles for gas volume fraction, gas velocity, bubble size and liquid temperature as well as axial profiles of wall temperature. After reviewing the theoretical and experimental basis of correlations used in the ANSYS CFX model used for the calculations, we give a careful assessment of the necessary recalibrations to describe the DEBORA tests. The basic CFX model is validated by a detailed comparison to the experimental data for two selected test ca cases. Simulations with a single set of calibrated parameters are found to give reasonable quantitative agreement with the data for several tests within a certain range of conditions and reproduce the observed tendencies correctly. Several model refinements are then presented each of which is designed to improve one of the remaining deviations between simulation and measurements. Specifically we consider a homogeneous MUSIG model for the bubble size, modified bubble forces, a wall function for turbulent boiling flow and a partial slip boundary condition for the liquid phase. Finally, needs for further model developments are identified and promising directions discussed.
    Źródło:
    Archives of Thermodynamics; 2012, 33, 1; 107-122
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical analysis of erosion wear and pressure drop for turbulent multiphase slurry flow
    Autorzy:
    Kannojiya, V.
    Darshan, M. B.
    Chandra, Y. P.
    Powiązania:
    https://bibliotekanauki.pl/articles/139624.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    erosion
    computational fluid dynamics
    CFD
    multi-phase flow
    pressure drop
    erozja
    obliczeniowa mechanika płynów
    przepływ wielofazowy
    spadek ciśnienia
    Opis:
    The disposal of ash in a thermal plant through the slurry pipe is subjected to some erosion wear due to the abrasive characteristics of the slurry. A simulation study of particle-liquid erosion of mild steel pipe wall based on CFD-FLUENT that considers the solid-liquid, solid-solid and solid-wall interaction is presented in this work.The multi-phase Euler-Lagrange model with standard k- ϵ turbulence modeling is adopted to predict the particulate erosion wear caused by the flow of bottom ash water suspension. Erosion rate for different particle size and concentration is evaluated at variable flow rate. It is observed that the pressure drop and erosion rate share direct relationships with flow velocity, particle size and concentration. The flow velocity is found to be the most influencing parameter. A model capable of predicting the erosion wear at variable operating conditions is presented.The simulation findings show good agreement with the published findings.
    Źródło:
    Archive of Mechanical Engineering; 2018, LXV, 3; 361-378
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance Investigation of a Double Pipe Heat Exchanger under Different Flow Configuration by Using Experimental and Computational Technique
    Autorzy:
    Kannojiya, V.
    Gaur, R.
    Yadav, P.
    Sharma, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/139516.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    heat exchanger
    computational fluid dynamics CFD
    FLUENT code
    parallel-counter flow
    wymiennik ciepła
    obliczeniowa mechanika płynów
    kod FLUENT
    równoległy przepływ przeciwprądowy
    Opis:
    Heat exchangers are widely employed in numerous industrial applications to serve the heat recovery and cooling purpose. This work reports a performance analysis of a tube in tube heat exchanger for different flow configuration under variable operating conditions. The experimental investigation was performed on a U-shaped double pipe heat exchanger set up whereas Commercial Computational Fluid Dynamics code FLUENT along with k-ε turbulence modeling scheme was implemented for the simulation study. The flow solution was achieved by implementing k-ε turbulence modeling scheme and the simulation findings were compared with the experimental results. The experimental findings were in good agreement with the simulation results. The counter-flow configuration was found to be 29.4% more effective than the cocurrent one at low fluid flow rate. Direct relationship between heat transfer rate and flow rate is observed while effectiveness and LMTD showed inverse relationship with it. The significance of inlet temperature of hot and cold stream has been evaluated, they play crucial role in heat exchange process.
    Źródło:
    Archive of Mechanical Engineering; 2018, LXV, 1; 27-41
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Free Vibration Analysis of Mindlin Plates Resting on Pasternak Foundation Using Coupled Displacement Method
    Autorzy:
    Rajesh, K.
    Saheb, K. M.
    Powiązania:
    https://bibliotekanauki.pl/articles/139827.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    fundamental frequency parameter
    Mindlin plate
    linear free vibrations
    computational fluid dynamics
    CFD
    Pasternak foundation
    parametr częstotliwości podstawowej
    płyta Mindlina
    liniowe drgania swobodne
    obliczeniowa mechanika płynów
    podłoże Pasternaka
    Opis:
    The authors developed a simple and efficient method, called the Coupled Displacement method, to study the linear free vibration behavior of the moderately thick rectangular plates in which a single-term trigonometric/algebraic admissible displacement, such as total rotations, are assumed for one of the variables (in both X,Y directions), and the other displacement field, such as transverse displacement, is derived by making use of the coupling equations. The coupled displacement method makes the energy formulation to contain half the number of unknown independent coefficients in the case of a moderately thick plate, contrary to the conventional Rayleigh-Ritz method. The smaller number of undetermined coefficients significantly simplifies the vibration problem. The closed form expression in the form of fundamental frequency parameter is derived for all edges of simply supported moderately thick rectangular plate resting on Pasternak foundation. The results obtained by the present coupled displacement method are compared with existing open literature values wherever possible for various plate boundary conditions such as all edges simply supported, clamped and two opposite edges simply supported and clamped and the agreement found is good.
    Źródło:
    Archive of Mechanical Engineering; 2018, LXV, 1; 107-128
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An evaluation of turbulence model for vortex breakdown detection over delta wing
    Autorzy:
    Wibowo, S. B.
    Sutrisno, -
    Rohmat, T. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/949942.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    turbulence models
    vortex breakdown
    delta wing
    vortex core
    computational fluid dynamics
    CFD
    roll-up vortex
    modele turbulencji
    awaria wirowa
    skrzydło delta
    rdzeń vortex
    obliczeniowa mechanika płynów
    wir zawijający
    Opis:
    An important phenomenon of delta wing is the mechanism of vortex core, which indicates the increase in lifting force until the occurrence of the vortex breakdown. The computational fluid dynamics (CFD) is very helpful in visualizing and providing analysis of the detailed data. The use of turbulent models will affect the quality of results in obtaining the vortex breakdown phenomenon. This study used several models of turbulence to capture the occurrence of vortex breakdown and compare it with experiments using water tunnel test facility. The results show that all turbulence models give good results at a low angle of attack (AoA), but at a high AoA the DES model gives the results closest to experimental ones with Cl error value of about 1 %. Taking into account the time required and the acceptable level of accuracy, the use of SST and k-ω models is an alternative option for use in the detection of vortex breakdown.
    Źródło:
    Archive of Mechanical Engineering; 2018, LXV, 3; 399-415
    0004-0738
    Pojawia się w:
    Archive of Mechanical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-8 z 8

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