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    Wyświetlanie 1-7 z 7
    Tytuł:
    Numerical study of fuel and turbulence distributions in an automotive-sized scavenged pre-chamber
    Autorzy:
    Bolla, Michele
    Shapiro, Evgeniy
    Kotzagianni, Maria
    Kyrtatos, Panagiotis
    Tiney, Nick
    Boulouchos, Konstantinos
    Powiązania:
    https://bibliotekanauki.pl/articles/133134.pdf
    Data publikacji:
    2019
    Wydawca:
    Polskie Towarzystwo Naukowe Silników Spalinowych
    Tematy:
    scavenged prechamber
    Reynolds-averaged Navier-Stokes
    RANS
    large-eddy simulation
    LES
    mixture formation
    oczyszczona komora wstępna
    tworzenie mieszanki
    Opis:
    This article presents a numerical study of the fuel and turbulence distributions in a pre-chamber at spark-time. The study has been conducted in the framework of the H2020 Gas-On project, dealing with the development of a lean-burn concept for an automotive-sized gas engine equipped with a scavenged pre-chamber. The test case considered studies a 7-hole pre-chamber with circumferentially-tilted orifices mounted on the cylinder head of a rapid compression-expansion machine (RCEM), consistent with the experimental test rig installed at ETH Zurich. An accurate description of turbulence and fuel distributions are key quantities determining the early flame development within the pre-chamber. Both quantities have an influence on the overall combustion characteristics and therefore on the engine performance. For this purpose, computational fluid dynamics (CFD) is employed to complement experimental investigations in terms of data completeness. The performance of the Reynolds-averaged Navier-Stokes (RANS)-based turbulence model is compared with large-eddy simulation (LES) through ensemble averaging of multiple LES realizations, in which the fuel injection rate evolution into the pre-chamber has been perturbed. Overall, RANS results show that the distributions of the turbulent kinetic energy and fuel concentration at spark-time agree well with the LES ensemble-averaged counterparts. This constitutes a prerequisite in view of the combustion phase and the accuracy reported provides further confidence in this regard.
    Źródło:
    Combustion Engines; 2019, 58, 1; 61-67
    2300-9896
    2658-1442
    Pojawia się w:
    Combustion Engines
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical study of hydrodynamic derivatives and course stability under ship-bank interaction
    Autorzy:
    Liu, H.
    Ma, N.
    Gu, X. C.
    Powiązania:
    https://bibliotekanauki.pl/articles/116925.pdf
    Data publikacji:
    2018
    Wydawca:
    Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
    Tematy:
    safety at sea
    ship-bank interaction
    Reynolds-Averaged Navier-Stokes (RANS)
    hydrodynamic derivatives
    hydrodynamics
    Planar Motion Mechanism (PMM)
    Circulating Water Channel (CWC)
    User Defined Functions (UDF)
    Opis:
    Since ship-bank interaction affects the manoeuvrability of a ship navigating close to a bank, the determination of hydrodynamic derivatives is of great importance to assess the ship manoeuvrability. To obtain the hydrodynamic derivatives of the KVLCC2 model ship with different water depths and ship-bank distances, the simulation of PMM tests are carried out using an unsteady Reynolds-Averaged Navier–Stokes (RANS) based solver. Hybrid dynamic mesh technique is proposed to realize the simulation of pure yaw tests in confined water. Studies on the grid convergence and time-step-size convergence are firstly performed. Hydrodynamic derivatives for the ship in different water depths and ship-bank distances are compared. The course stability is investigated based on time-domain simulations and eigenvalue analysis, and the results show that the ship-bank interaction and shallow water effect have a remarkable influence on the course stability.
    Źródło:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2018, 12, 4; 747-753
    2083-6473
    2083-6481
    Pojawia się w:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Implementation of turbulence damping in the OpenFOAM multiphase flow solver interFoam
    Autorzy:
    Polansky, Jiri
    Schmelter, Sonja
    Powiązania:
    https://bibliotekanauki.pl/articles/2091357.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    multiphase flow
    stratified flow
    turbulence damping
    computational fluid dynamics
    OpenFOAM
    Reynolds-averaged Navier–Stokes
    Detached Eddy Simulation
    Delayed Detached Eddy Simulation
    Opis:
    In the presented work Egorov’s approach (adding a source term to the ω-equation in the k-ω model, which mimics the damping of turbulence close to a solid wall) was implemented in on the subclass of shear stress transport models. Hence, turbulence damping is available for all shear stress transport type models, including hybrid models that are based on the ω-equation. It is shown that turbulence damping improves the prediction of the axial velocity profile not only for Reynolds-averaged Navier–Stokes simulation but also for detached eddy simulation and delayed detached eddy simulation models. Furthermore, it leads to a more realistic estimation of the pressure drop and, hence, to a more correct prediction of the liquid level. In this paper, simulation results for four different turbulence models are presented and validated by comparison with experimental data. Furthermore, the influence of the magnitude of the damping factor on the pressure drop in the channel is investigated for a variety of different gas-to-liquid flow rate ratios. These investigations show that higher gas-to-liquid flow rate ratios require higher damping factors to correctly predict the pressure drop. In the end, advice is formulated on how an appropriate damping factor can be determined for a specific test case.
    Źródło:
    Archives of Thermodynamics; 2022, 43, 1; 21--43
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental and numerical determination of the hydrodynamic coefficients of an autonomous underwater vehicle
    Autorzy:
    Sakaki, Abdollah
    Kerdabadi, Mohsen Sadeghian
    Powiązania:
    https://bibliotekanauki.pl/articles/135543.pdf
    Data publikacji:
    2020
    Wydawca:
    Akademia Morska w Szczecinie. Wydawnictwo AMSz
    Tematy:
    Reynolds averaged Navier–Stokes
    computational fluid dynamics
    linear coefficients
    non-linear coefficients
    underwater vehicle
    Opis:
    Computational fluid dynamics (CFD) has progressed rapidly in the past fifty years and is now used in many industrial fields, such as air, space, and marine engineering. CFD has an irreplaceable role in marine design and scientific research, and its applications within this field continue to grow with the development of computers. CFD is used to quickly and inexpensively simulate fluid behaviour using the Reynolds Averaged Navier–Stokes (RANS) equations to calculate hydrodynamic coefficients, which are needed in manoeuvrability studies of underwater vehicles (UWV). Here, these computations are performed for six geometrical shapes that represent typical autonomous underwater vehicles (AUVs) currently in use. Resistance test simulations at up to 20o drift angles were conducted for AUVs with different length-to-diameter ratios. The results were compared with the experimental data and current quasi-experimental relationships, which suggested that the CFD predictions were adequately precise and accurate. These predictions indicated that there was a non-linear relationship between forces and moments and the lateral speed. Moreover, both linear and non-linear hydrodynamic coefficients were calculated.
    Źródło:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2020, 62 (134); 124-135
    1733-8670
    2392-0378
    Pojawia się w:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Two-dimensional vertical Reynolds-Averaged Navier-Stokes equations versus one-dimensional Saint-Venant model for rapidly varied open channel water flow modelling
    Autorzy:
    Szydłowski, M.
    Zima, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/241158.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
    Tematy:
    mathematical modelling
    Reynolds-averaged Navier-Stokes equations
    Saint-Venant equations
    free surface flow
    rapidly varied flow
    dam-break problem
    Opis:
    The paper concerns mathematical modelling of free surface open channel water flow. In order to simulate the flow two models are used -- two-dimensional vertical Reynolds-Averaged Navier-Stokes equations and one-dimensional Saint-Venant equations. The former is solved with SIPMLE algorithm of finite difference method using Marker and Cell technique to trace a free surface movement. The latter is solved using the finite volume method. The dam-break (water column collapse) problem on horizontal bottom is investigated as a test case. The calculated results are compared with each other. The numerical simulations are examined against laboratory experiment presented by Koshizuka et al (1995). The possibility of using the described models to simulate rapidly varied flow is discussed.
    Źródło:
    Archives of Hydro-Engineering and Environmental Mechanics; 2006, 53, 4; 295-309
    1231-3726
    Pojawia się w:
    Archives of Hydro-Engineering and Environmental Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Validation of a flow channel to investigate velocity profiles of friction-reducing ship coatings
    Autorzy:
    Weisheit, J.
    Schneider, V. E.
    Serr, J. M.
    Hagemeister, N.
    Oeffner, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1841545.pdf
    Data publikacji:
    2021
    Wydawca:
    Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
    Tematy:
    ship coatings
    flow Channel
    vessel velocity
    laser Doppler velocimeter
    computational fluid dynamics
    AIRCOAT project
    reynolds averaged navier stokes
    measurement volume
    Opis:
    Reducing friction with specialised hull coatings or air lubrication technologies has a potential reducing energy consumption and emissions in shipping. The EU project AIRCOAT combines both by developing a passive air lubrication technology inspired by nature that is implemented on a self-adhesive foil system. Besides validating the friction reduction it is of high interest to understand the underlying mechanism that causes the reduction. Therefore, a flow channel was designed, that creates a stationary turbulent flow within a square duct allowing for non-invasive measurements by laser doppler velocimetry. The high spatial resolution of the laser device makes recording velocity profiles within the boundary layer down to the viscous sublayer possible. Determination of the wall shear stress τ enables direct comparison of different friction reduction experiments. In this paper we validate the methodology by determining the velocity profile of the flat channel wall (without coatings). We further use the results to validate a CFD model in created in OpenFOAM. We find that velocities along the longitudinal axis are generally in good agreement between numerical and experimental investigations.
    Źródło:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2021, 15, 1; 225-231
    2083-6473
    2083-6481
    Pojawia się w:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Two-dimensional vertical analysis of dam-break flow
    Autorzy:
    Zima, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1933149.pdf
    Data publikacji:
    2007
    Wydawca:
    Politechnika Gdańska
    Tematy:
    mathematical modeling
    Reynolds-averaged Navier-Stokes equations
    rapidly varied free surface flow
    dam-break flow
    Opis:
    The paper concerns mathematical modeling of free surface open-channel water flow. Two-dimensional vertical Reynolds-averaged Navier-Stokes equations were used to simulate the flow. They were solved with the SIMPLE algorithm of the finite difference method using the Marker and Cell technique to trace free surface movement. The dam-break flow (water column collapse) problem on a horizontal and frictionless bottom was investigated as a test case. The mechanics of dam-break flow for wet and dry bed conditions was analyzed on the basis of numerical simulations. The obtained results are shown for varying head of water in the downstream channel. The possibility of using the shallow-water equations and the RANS model to simulate rapidly varied flows is discussed.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2007, 11, 4; 315-328
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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