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Wyszukujesz frazę "Ghassemi, H." wg kryterium: Autor

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    Tytuł:
    Hydrodynamic performance of coaxial contra-rotating propeller (CCRP) for large ships
    Autorzy:
    Ghassemi, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/258620.pdf
    Data publikacji:
    2009
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    boundary element method
    contra-rotating propeller
    CRP
    optimum efficiency
    Opis:
    This paper describes a coaxial contra-rotating propeller (CCRP) system to calculate the hydrodynamic characteristics and then obtain the optimum operational condition to install on two different large bulk carrier and VLCC. The method is based on boundary element method (BEM) to obtain the hydrodynamic performance of any complicated configuration such as CRP system, and then the optimum propeller data is obtained by the systematical method at the design condition. We prepared a software package code, namely SPD (Ship Propeller Design), which has model mesh generation, solver and numerical output results. The comparison of the propulsive performance was made between the propeller alone and CRP arrangement. Major finding include good agreement between predictions using the numerical code and experimental data for both ships.
    Źródło:
    Polish Maritime Research; 2009, 1; 22-28
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical calculations of the hydrodynamic performance of the contra-rotating propeller (CRP) for high speed vehicle
    Autorzy:
    Ghassemi, H.
    Taherinasab, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/259593.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    boundary element method
    contra-rotating propeller
    high speed vehicle
    Opis:
    Several different methods have been used to analyze the marine propellers. In this paper a boundary element method (BEM) for modelling steady hydrodynamic performance of a contra-rotating propeller (CRP) has been developed. The potential flow across the front and rear propellers have been considered. By calculating the induced flow, the interaction between two propellers is studied. This method has been applied to a typical CRP. The results are included in the form of the hydrodynamic performance coefficients, total thrust and torques. Numerical calculations indicate that the predicted hydrodynamic performance shows good conformity with experimental results.
    Źródło:
    Polish Maritime Research; 2013, 2; 13-20
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Boundary element method applied to added mass coefficient calculation of the skewed marine propellers
    Autorzy:
    Yari, E.
    Ghassemi, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/260213.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    added mass coefficient
    boundary element method
    skew marine propeller
    Opis:
    The paper mainly aims to study computation of added mass coefficients for marine propellers. A three-dimensional boundary element method (BEM) is developed to predict the propeller added mass and moment of inertia coefficients. Actually, only few experimental data sets are available as the validation reference. Here the method is validated with experimental measurements of the B-series marine propeller. The behavior of the added mass coefficients predicted based on variation of geometric and flow parameters of the propeller is calculated and analyzed. BEM is more accurate in obtaining added mass coefficients than other fast numerical methods. All added mass coefficients are nondimensionalized by fluid density, propeller diameter, and rotational velocity. The obtained results reveal that the diameter, expanded area ratio, and thickness have dominant influence on the increase of the added mass coefficients.
    Źródło:
    Polish Maritime Research; 2016, 2; 25-31
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Outlier detection in ocean wave measurements by using unsupervised data mining methods
    Autorzy:
    Mahmoodi, K.
    Ghassemi, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/260330.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    ocean wave data
    data mining
    outlier detection
    data correction
    Opis:
    Outliers are considerably inconsistent and exceptional objects in the data set that do not adapt to expected normal condition. An outlier in wave measurements may be due to experimental and configuration errors, technical defects in equipment, variability in the measurement conditions, rare or unknown conditions such as tsunami, windstorm and etc. To improve the accuracy and reliability of an built ocean wave model, or to extract important and valuable information from collected wave data, detecting of outlying observations in wave measurements is very important. In this study, three typical outlier detection algorithms:Box-plot (BP), Local Distance-based Outlier Factor (LDOF), and Local Outlier Factor (LOF) methods are used to detect outliers in significant wave height (Hs) records. The historical wave data are taken from National Data Buoy Center (NDBC). Finally, those data points are considered as outlier identified by at least two methods which are presented and discussed. Then, Hs prediction has been modelled with and without the presence of outliers by using Regression trees (RTs).
    Źródło:
    Polish Maritime Research; 2018, 1; 44-50
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Added Mass Coefficient computation of sphere, ellipsoid and marine propellers using Boundary Element Method
    Autorzy:
    Ghassemi, H.
    Yari, E. M.
    Powiązania:
    https://bibliotekanauki.pl/articles/259317.pdf
    Data publikacji:
    2011
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    Added mass coefficient
    boundary element method
    ellipsoid
    Opis:
    Added mass is an important and effective dynamic coefficient in accelerating, non uniform motion as a result of fluid accelerating around a body. It plays an important role, especially in vessel roll motion, control parameters as well as in analyzing the local and global vibration of a vessel and its parts like propellers and rudders. In this article, calculating the Added Mass Coefficient has been examined for a sphere, ellipsoid, marine propeller and hydrofoil; using numerical Boundary Element Method. Since an Ellipsoid and a sphere have simple geometric shapes and the Analytical values of their added mass coefficients are available, so that the results of added mass matrix are obtained and evaluated, using the boundary element method. Then the added mass matrix is computed in a given geometrical and flow specifications for a specific propeller and its results are studied versus experimental results, which it’s current numerical data In comparison with other numerical methods has a good conformity with experimental results. The most important advantage of the method in determining the added mass matrix coefficients for the surface and underwater vessels and the marine propellers is extracting all the added mass coefficients with very good Accuracy, while in other numerical methods it is impossible to extract all the coefficients with the Desired Accuracy.
    Źródło:
    Polish Maritime Research; 2011, 1; 17-26
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical Analysis of Hub Effect on ydrodynamic Performance of Propellers with Inclusion of PBCF to Equalize the Induced Velocity
    Autorzy:
    Ghassemi, H.
    Mardan, A.
    Ardeshir, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/259001.pdf
    Data publikacji:
    2012
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    propeller hub
    induced velocities
    hub vortex
    PBCF
    Opis:
    In this article the boundary element method (BEM) is applied to analyze the propeller hub as a non-lifting body and the blades in its vicinity as lifting bodies. In solver, the geometrical modeling of hub, blades are PBCF (Propeller Boss Cap Fin) constructed by quadrilateral elements. The velocity potential is determined on each element by discretized boundary integral equation. Iterative procedure is used to consider the adjacent body effect. In each step the body was independently analyzed with the influence of near body considered in inflow velocity. The induced velocity of propeller was calculated with and without PBCF in downstream. PBCF, an energy-saving device, reduces and uniforms the induced velocity of propeller in downstream. Numerical results of propeller hydrodynamic characteristics including hub effect, induced velocities, PBCF influence are presented.
    Źródło:
    Polish Maritime Research; 2012, 2; 17-24
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical prediction of wave patterns due to motion of 3D bodies by Kelvin-Havelock sources
    Autorzy:
    Ghassemi, H.
    Ghamari, I.
    Ashrafi, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/259373.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    free surface waves
    Boundary Element Method (BEM)
    Kelvin-Havelock source
    Opis:
    This paper discusses the numerical evaluation of the hydrodynamic characteristics of submerged and surface piercing moving bodies. Generally, two main classes of potential methods are used for hydrodynamic characteristic analysis of steady moving bodies which are Rankine and Kelvin-Havelock singularity distribution. In this paper, the KelvinHavelock sources are used for simulating the moving bodies and then free surface wave patterns are obtained. Numerical evaluation of potential distribution of a Kelvin-Havelock source is completely presented and discussed. Numerical results are calculated and presented for a 2D cylinder, single source, two parallel moving source, sphere, ellipsoid and standard Wigley hull in different situation that show acceptable agreement with results of other literatures or experiments.
    Źródło:
    Polish Maritime Research; 2016, 4; 46-58
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of material on hydro-elastic behavior of marine propeller by using BEM-FEM hybrid software
    Autorzy:
    Ghassemi, H.
    Ghassabzadeh, M.
    Saryazdi, M. Gh.
    Powiązania:
    https://bibliotekanauki.pl/articles/259501.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    hydro-elasticity
    propeller characteristics
    deformed blade
    HYDRO-BEM software
    ELASTIC-FEM software
    Opis:
    This paper studies the effect of material on the hydro-elastic behaviour. The geometry of flexible propeller changes due to hydrodynamic and inertial forces acting on the propeller. By using prepared software (called HYDRO-BEM and ELASTIC-FEM) the hydro-elastic features of the propeller made of various materials are analyzed. In the software the hybrid boundary element and finite element methods are used. First, the load acting on the propeller is determined by using the BEM and deformed propeller geometry is then obtained by the FEM. In the next step, the load on the deformed propeller is determined by the BEM and a new shape is obtained. The iterative procedure is repeated till the blade deflection and hydrodynamic characteristics (thrust, torque and efficiency) of the propeller become converged. Four different materials are examined. It is concluded that the hydro-elastic behaviour of the composite propeller is strongly affected by its flexibility due to light material.
    Źródło:
    Polish Maritime Research; 2013, 4; 62-70
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A hydrodynamic methodology and CFD analysis for performance prediction of stepped planing hulls
    Autorzy:
    Ghassemi, H.
    Kamarlouei, M.
    Veysi, S. T. G.
    Powiązania:
    https://bibliotekanauki.pl/articles/260311.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    planing hull
    Hydrodynamic performance
    CFD analyzed
    Opis:
    Nowadays all efforts in planing hull research are focused on resistance reduction for achieving the highest speed in fast planing crafts. Furthermore, many fruitful research projects have been carried out on marine coatings, planning equipment, and optimization of propeller and hull form, which revolutionized industry of high - speed crafts and made them an efficient survival vehicle in coastal areas and rivers. In this paper the hydrodynamic performance of planing hulls are investigated by means of a modified Savitsky model for both non-stepped and stepped bodies. Meanwhile, in order to meet this goal reasonably, effective geometrical parameters of planing hull are investigated and then operational hydrodynamic characteristics of the craft are predicted by using a computational program. Finally, the calculation results are verified by means of a CFD- analysis model.
    Źródło:
    Polish Maritime Research; 2015, 2; 23-31
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Neural network-PID controller for roll fin stabilizer
    Autorzy:
    Ghassemi, H.
    Dadmarzi, F. H.
    Ghadimi, P.
    Ommani, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/259283.pdf
    Data publikacji:
    2010
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    Fin stabilizer
    neural network
    PID control
    restoring force
    Opis:
    Fin stabilizers are very effective devices for controlling the ship roll motion against external wave-generated moments. Lift forces due to flow around fin with an angle of attack produce anti - roll moment. Therefore control of attack angle plays important role in reducing roll of ships. This paper presents results of using a combined neural network and PID for roll control of ship with small draught. Numerical results are given of around-fin flow analysis with considering free surface effect modelled by neural network and imposed to controlling loop. Hydraulic machinery constraints are also considered in the modelling. The obtained results show good performance of the controller in reducing roll amplitude in random seas. The approach can be used for any irregular sea conditions.
    Źródło:
    Polish Maritime Research; 2010, 2; 23-28
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-10 z 10

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