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    Wyświetlanie 1-3 z 3
    Tytuł:
    Shape optimization of a hydrofoil with leadingedge protuberances using full factorial sweep sampling and an RBF surrogate model
    Autorzy:
    Nazemian, Amin
    Ghadimi, Parviz
    Powiązania:
    https://bibliotekanauki.pl/articles/135182.pdf
    Data publikacji:
    2020
    Wydawca:
    Akademia Morska w Szczecinie. Wydawnictwo AMSz
    Tematy:
    humpback whale flippers
    leading-edge protuberances
    free-form deformation (FFD)
    surrogate model
    CFD
    lift-to-drag ratio (L/D)
    Opis:
    This paper investigates improving the leading-edge of a hydrofoil with sinusoidal protuberances based on its hydrodynamic performance. The original hydrofoil geometry was inspired by the leading edge of the flipper of a humpback whale. A multi-step optimization process was performed for a 634-021 hydrofoil. The free-form deformation technique defined the shape parameters as a variable design, and these parameters included the amplitude of the leading-edge protuberances, which ranged from 0 to 20% of the chord length, and the corrugate span, with 3 and 4 crests. The flow characteristics of a parametric hydrofoil were examined using a CFD solver, and the lift, drag, and lift-to-drag ratio (L/D) were computed as responses to the optimization cycle. To accomplish this, two design study methods were sequentially applied at different angles of attack. A full factorial design sweep tool was applied that went through all parameter value combinations, and an RBF-based surrogate model was constructed to investigate the system behavior. The results indicated the existence of an optimum design point, and the highest L/D ratio was determined to be 10.726 at a 12° angle of attack.
    Źródło:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2020, 62 (134); 116-123
    1733-8670
    2392-0378
    Pojawia się w:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical simulation of the seakeeping of a military trimaran hull by a novel overset mesh method in regular and irregular waves
    Autorzy:
    Ghadimi, Parviz
    Karami, Saeid
    Nazemian, Amin
    Powiązania:
    https://bibliotekanauki.pl/articles/1818907.pdf
    Data publikacji:
    2021
    Wydawca:
    Akademia Morska w Szczecinie. Wydawnictwo AMSz
    Tematy:
    trimaran
    hydrodynamic performance
    seakeeping
    overset mesh
    numerical simulation
    regular and irregular waves
    Opis:
    The hydrodynamic performance of trimaran hulls has been previously investigated for optimum performance in calm water, but there is still a limited understanding of its motion response; therefore, a CFD-based numerical approach was developed and applied on a trimaran hull in the presence of regular and irregular waves. To validate the CFD method, a comparison was conducted using both experimental and 3D panel method data. In this study, two different turbulence models were surveyed, and the SST Menter k-Omega (k-ω) turbulence model was shown to be a more accurate model than the realizable k-Epsilon (k-ε) model. The different features of the proposed numerical model include the implementation of an overset mesh method, unique mesh plan refinement, and wave-damping region. The discrepancy between the experimental data and the results of other seakeeping calculation methods have always been problematic, especially for low-speed strip theory and 3D panel methods, but good consistency was observed between the proposed CFD model and experimental data. Unlike potential-based or conformal mapping seakeeping analysis methods, the effect of nonlinear waves, hull shape above the waterline, and other ship dynamic phenomena were considered in this CFD application. The proposed CFD method reduces the simulation time and computational efforts for ship motion calculations.
    Źródło:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2021, 65 (137); 38-50
    1733-8670
    2392-0378
    Pojawia się w:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Shape optimization of a submerged 2D hydrofoil and improvement of its lift-to-drag ratio using CFDbased mesh morphing-adjoint algorithm
    Autorzy:
    Nazemian, Amin
    Ghadimi, Parviz
    Ghadimi, Aliakbar
    Powiązania:
    https://bibliotekanauki.pl/articles/24202520.pdf
    Data publikacji:
    2022
    Wydawca:
    Akademia Morska w Szczecinie. Wydawnictwo AMSz
    Tematy:
    NACA0012 hydrofoil
    free surface
    lift-to-drag ratio
    Ansys-Fluent
    mesh morphing
    adjoint solver
    Opis:
    Hydrofoils are utilized as instruments to improve the hydrodynamic performance of marine equipment. In this paper, the motion of a 2D NACA0012 hydrofoil advancing in water near the free surface was simulated, and a mesh morphing-adjoint based optimizer was used to maximize its lift-to-drag ratio. Ansys-Fluent was used as a CFD solver, and a mesh-morphing tool was used as a geometry reconstruction tool. Furthermore, the Adjoint solver was applied to evaluate the sensitivities of the objective function to all solution variables. Defined control points around the geometry are design variables that move in an appropriate direction through shape sensitivity. The computational results were validated against available experimental data and published numerical findings. Subsequently, different hydrodynamic characteristics of the optimized hydrofoil were compared to those of the original model at different angles of attack of 3, 3.5, 4, 4.5, 5, 5.5, 6, and 6.5°, and optimized shapes were determined. It was observed that the shape of the optimized hydrofoil was totally dependent on the angle of attack, which produced different lift-to-drag ratios. It is also seen that among higher angles of attack at which improvement in the L/D ratio became steady, the drag coefficient was the lowest at 5°. Therefore, it can be concluded that the appropriate angle of attack for a hydrofoil installation on the ship hull is 5°. Further investigation was conducted concerning the evolution of shape optimization, sensitivity analysis, free surface elevation, flow characteristics, and hydrodynamic performance of the hydrofoil at a 5° angle of attack.
    Źródło:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2022, 70 (142); 27--40
    1733-8670
    2392-0378
    Pojawia się w:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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