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


Tytuł:
Practical approach to calculating the hydrodynamic oscillating loads of a ship propeller under non-uniform wake field
Autorzy:
Ghassemi, H.
Powiązania:
https://bibliotekanauki.pl/articles/906061.pdf
Data publikacji:
2018
Wydawca:
Akademia Morska w Szczecinie. Wydawnictwo AMSz
Tematy:
hydrodynamic performance
non-uniform wake
oscillating thrust and torque
practical approach
ship propeller
ship design
Opis:
Propellers usually operate in the ship’s stern, where the inflow of the non-uniform wake generates oscillating loads and changes the hydrodynamic performance. Therefore, determination of the forces on propellers and hydrodynamic performance due to a non-uniform wake field are the challenging problems for naval architects and hydrodynamists. The main objectives of the present study are to assess the hydrodynamic performance for a single blade and all the blades. The propeller is a B-series propeller under non-uniform wake field behind the Seiun-Maru (hereafter SM) ship hull. A practical approach is employed to calculate the hydrodynamic oscillating loads of the ship propeller under a non-uniform wake field. Results of the computations on the propeller behind the SM ship, due to a non-uniform wake field, are presented and analyzed using classical mathematical methods over a single cycle. The results show that a variation of thrust with the discussed parameters is the same as that shown for torque, also the blade-frequency of the total force, thrust and torque is an increasing function of radial sections, whereas these parameters decrease with increasing radial blade sections.
Źródło:
Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2018, 56 (128); 9-20
1733-8670
2392-0378
Pojawia się w:
Zeszyty Naukowe Akademii Morskiej w Szczecinie
Dostawca treści:
Biblioteka Nauki
Artykuł
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:
Hydrodynamic multidisciplinary optimization of a container ship and its propeller using comprehensive HPSOP code
Autorzy:
Zakerdoost, H.
Ghassemi, H.
Powiązania:
https://bibliotekanauki.pl/articles/135637.pdf
Data publikacji:
2018
Wydawca:
Akademia Morska w Szczecinie. Wydawnictwo AMSz
Tematy:
hydrodynamic optimization
marine propeller
container ship
hull resistance
ship industry
open water efficiency
Opis:
Hydrodynamic shape optimization plays an increasingly important role in the shipping industry. To optimize ship hull and propeller shapes for minimum total (friction+wave) calm-water resistance and maximum open water efficiency, respectively, the main particulars of a hull and propeller model are considered as design variables. The optimization problem is performed by using an integrated hull-propeller system optimization problem (HPSOP) code in a multi-level and multi-point methodology in early-stage ship design. Three numerical methods with variable fidelity are employed to carry out the hydrodynamic performance analysis of a ship’s hull and propeller. A ship and its propeller are selected as initial models to illustrate the effectiveness of the proposed optimization procedure. The numerical results show that the developed technique is efficient and robust for hydrodynamic design problems.
Źródło:
Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2018, 53 (125); 48-56
1733-8670
2392-0378
Pojawia się w:
Zeszyty Naukowe Akademii Morskiej w Szczecinie
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:
Numerical analysis of the hydrodynamic characteristics of the accelerating and decelerating ducted propeller
Autorzy:
Razaghian, A. H.
Ghassemi, H.
Powiązania:
https://bibliotekanauki.pl/articles/135301.pdf
Data publikacji:
2016
Wydawca:
Akademia Morska w Szczecinie. Wydawnictwo AMSz
Tematy:
accelerating and decelerating ducted propeller
pressure coefficient
hydrodynamics characteristics
Opis:
This paper investigates the open-water characteristics of the 5-blade propeller with accelerating and decelerating ducts using the Reynolds-Averaged Navier-Stokes (RANS) equation code. In the first step, numerical open-water hydrodynamic characteristics of the propeller in the absence of a duct were validated using the available experimental data. The shear stress transport (SST) turbulence model was chosen, which shows less error in thrust and torque coefficients than others. In the second step, two accelerating and decelerating ducts, namely ducts 19A and N32, were modeled. In these simulations, the clearance value was selected at 3 percent of the propeller’s diameter and uniform-flow conditions were assumed. After analysis of the mesh sensitivity for the propeller thrust, the results were compared to the corresponding open-water condition values. In this regard, results of the hydrodynamic coefficients, pressure distribution, and coefficients on the propeller-blade surface and ducts were also analyzed and discussed.
Źródło:
Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2016, 47 (119); 42-53
1733-8670
2392-0378
Pojawia się w:
Zeszyty Naukowe Akademii Morskiej w Szczecinie
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 study of step forward swept angle effects on the hydrodynamic performance of a planing hull
Autorzy:
Nourghasemi, H.
Bakhtiari, M.
Ghassemi, H.
Powiązania:
https://bibliotekanauki.pl/articles/135251.pdf
Data publikacji:
2017
Wydawca:
Akademia Morska w Szczecinie. Wydawnictwo AMSz
Tematy:
planing hull
step forward swept angle
hydrodynamic performance
drag
wake profile
RANS
Opis:
One of the most effective methods to diminish the drag of a planing craft is to use a step at the bottom of the hull. A stepped hull causes a reduction of the wetted area and, as a result, a decrease in the drag. The step may be designed as a straight line through the entire width of the hull or may be V-shaped with a forward or backward swept angle. In this paper, the effects of the step forward swept angle on the hydrodynamic performance of a hard chine planing vessel are investigated by finite volume method (FVM). Reynolds-Averaged Navier Stokes (RANS) equations with a standard k-ε turbulence model coupled with volume of fluid (VOF) equations are solved in order to simulate a transient turbulent free surface flow around the hull with the help of Ansys CFX software. In order to predict hull motions, equations of rigid body motions for two degrees of freedom (2-DOF) are coupled with fluid flow governing equations. To validate the presented numerical model, first the numerical results are compared with available experimental data, and then the obtained numerical results of the drag, dynamic trim, sinkage, wetted keel length, wetted chine length, pressure distribution on the hull, wetted surface and wake profile at different Froude numbers and step angles are presented and discussed.
Źródło:
Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2017, 51 (123); 35-42
1733-8670
2392-0378
Pojawia się w:
Zeszyty Naukowe Akademii Morskiej w Szczecinie
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hydrodynamic performance of the horizontal axis tidal stream turbine using RANS solver
Autorzy:
Ghassemi, H.
Ghafari, H.
Homayoun, E.
Powiązania:
https://bibliotekanauki.pl/articles/135593.pdf
Data publikacji:
2018
Wydawca:
Akademia Morska w Szczecinie. Wydawnictwo AMSz
Tematy:
tidal turbine
duct
number of blades
pressure
hydrodynamic performance
HATST
Opis:
This current work investigates the effect of duct and number of blades on the hydrodynamic performance of the horizontal axis tidal stream turbine (HATST). The numerical method based on Reynolds averaged Navier-Stokes (RANS) equations is employed to compare the hydrodynamic performance for various cases of this device. For validation of the numerical results, a 3-blade HATST without-duct has been compared against experimental data. The analysis and comparison of the simulation results show that using duct for HATST has increased the power coefficient, the torque coefficient, the trust coefficient, and the force on the blade. In addition, the simulation results of the cases with a greater number of blades shows that the trust coefficient increased and the force on the blade decreased. Therefore, it is recommended to use ducted HATST with a great number of blades to extract more energy from the tidal stream.
Źródło:
Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2018, 55 (127); 23-33
1733-8670
2392-0378
Pojawia się w:
Zeszyty Naukowe Akademii Morskiej w Szczecinie
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical calculations of the potential on the rectangular and ellpitic domains with various aspect ratios
Autorzy:
Panahi, S.
Ghassemi, H.
Nowruzi, H.
Powiązania:
https://bibliotekanauki.pl/articles/122978.pdf
Data publikacji:
2017
Wydawca:
Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
Tematy:
boundary element method
rectangular and elliptic domains
potential value
metoda elementów skończonych
równanie Laplace'a
współczynnik kształtu
Opis:
In the current study, the Laplace equation is solved for rectangular and elliptical computational domains by using the boundary element method (BEM). For this accomplishment, 120 different aspect ratios in a rectangular and elliptical computational domains are designed. The Dirichlet and Neumann boundary conditions are used respectively for a rectangular and elliptical domains. Also, the Gaussian quadrature integral method is applied to solve the influence coefficient matrix in BEM. To assess a different aspect ratio on the potential solution, two different measurement positions are intended. According to our finding, with an increase of the aspect ratio, the potential value is increased for both rectangular and elliptical domains. However, a potential increment with aspect ratio enhancement is more visible in the elliptical domain.
Źródło:
Journal of Applied Mathematics and Computational Mechanics; 2017, 16, 3; 73-83
2299-9965
Pojawia się w:
Journal of Applied Mathematics and Computational Mechanics
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:
Experimental Investigation into Parameters Influencing Roll Tensioning of Circular Saw Blades
Autorzy:
Heisel, U.
Stehle, T.
Ghassemi, H.
Powiązania:
https://bibliotekanauki.pl/articles/99653.pdf
Data publikacji:
2015
Wydawca:
Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Tematy:
circular saw
wood machining
cutting tool
metal forming
Opis:
Circular saw blades are rolled in the shape of a ring by special roll tensioning machines to improve the static and dynamic behaviour of steel saw blades. Plastic deformation and strain hardening in the roller track area cause residual stresses in the circular saw blade, which influence the static stiffness and the natural frequencies of the circular saw blade. Roll tensioning is one of the important parts when producing circular saws, especially in the production of thin circular saw blades. Although the influence of the roll tensioning process on the static and dynamic properties is well-known, it is interesting to further investigate the parameters influencing the roll tensioning process. This paper presents the influence of various parameters on the roll tensioning process, such as material properties, rolling force, contact condition between roller wheels and circular saw blade. These investigations help to find the optimisation ability of this process and to gain a better understanding of the relationships between roll tensioning processes and improved static and dynamic properties of thin saw blades.
Źródło:
Journal of Machine Engineering; 2015, 15, 1; 98-111
1895-7595
2391-8071
Pojawia się w:
Journal of Machine Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Data mining models to predict ocean wave energy flux in the absence of wave records
Autorzy:
Mahmoodi, K.
Ghassemi, H.
Nowruzi, H.
Powiązania:
https://bibliotekanauki.pl/articles/135663.pdf
Data publikacji:
2017
Wydawca:
Akademia Morska w Szczecinie. Wydawnictwo AMSz
Tematy:
ocean wave energy
meteorological parameters
GEP
LDBOD
DMM
modeling
Opis:
Ocean wave energy is known as a renewable energy resource with high power potential and without negative environmental impacts. Wave energy has a direct relationship with the ocean’s meteorological parameters. The aim of the current study is to investigate the dependency between ocean wave energy flux and meteorological parameters by using data mining methods (DMMs). For this purpose, a feed-forward neural network (FFNN), a cascade-forward neural network (CFNN), and gene expression programming (GEP) are implemented as different DMMs. The modeling is based on historical meteorological and wave data taken from the National Data Buoy Center (NDBC). In all models, wind speed, air temperature, and sea temperature are input parameters. In addition, the output is the wave energy flux which is obtained from the classical wave energy flux equation. It is notable that, initially, outliers in the data sets were removed by the local distribution based outlier detector (LDBOD) method to obtain the best and most accurate results. To evaluate the performance and accuracy of the proposed models, two statistical measures, root mean square error (RMSE) and regression coefficient (R), were used. From the results obtained, it was found that, in general, the FFNN and CFNN models gave a more accurate prediction of wave energy from meteorological parameters in the absence of wave records than the GEP method.
Źródło:
Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2017, 49 (121); 119-129
1733-8670
2392-0378
Pojawia się w:
Zeszyty Naukowe Akademii Morskiej w Szczecinie
Dostawca treści:
Biblioteka Nauki
Artykuł

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