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Wyświetlanie 1-11 z 11
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:
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:
Approximating the added resistance coefficient for a bulk carrier sailing in head sea conditions based on its geometrical parameters and speed
Autorzy:
Cepowski, T.
Powiązania:
https://bibliotekanauki.pl/articles/258482.pdf
Data publikacji:
2016
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
bulk carrier
resistance
added wave resistance
added resistance coefficient
regular wave
irregular wave
ship designing
preliminary design stage
artificial neural networks
approximation
forecasting
speed
waterplane area
waterplane coefficient
sample case
task
designing
Opis:
The article presents the mathematical function to calculate the added wave resistance transfer function for bulk carriers. Based on this function, the statistical mean added wave resistance generated by an irregular head wave with arbitrary statistical parameters can be forecasted. The input parameters are: waterplane area, waterplane coefficient, ship speed, and frequency of the regular wave. The model has been developed based on the theory of artificial neural networks. The presented function can be used in design analyses, and for planning shipping routes in situations when basic geometrical parameters of the hull are only available and not the full technical documentation. The article presents sample cases of use of this function to calculate the added wave resistance transfer function and the statistical mean added wave resistance. Another presented application refers to waterplane coefficient optimisation taking into account the added wave resistance at the stage of preliminary bulk carrier design.
Źródło:
Polish Maritime Research; 2016, 4; 8-15
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Water-exit process modeling and added-mass calculation of the submarine-launched missile
Autorzy:
Yang, J.
Feng, J.
Li, Y.
Liu, A.
Hu, J.
Ma, Z.
Powiązania:
https://bibliotekanauki.pl/articles/260251.pdf
Data publikacji:
2017
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
submarine-launched missile
fluid-structure interaction
water-exit dynamic model
time-varying added-mass
numerical simulation
Opis:
In the process that the submarine-launched missile exits the water, there is the complex fluid solid coupling phenomenon. Therefore, it is difficult to establish the accurate water-exit dynamic model. In the paper, according to the characteristics of the water-exit motion, based on the traditional method of added mass, considering the added mass changing rate, the water-exit dynamic model is established. And with help of the CFX fluid simulation software, a new calculation method of the added mass that is suit for submarine-launched missile is proposed, which can effectively solve the problem of fluid solid coupling in modeling process. Then by the new calculation method, the change law of the added mass in water-exit process of the missile is obtained. In simulated analysis, for the water-exit process of the missile, by comparing the results of the numerical simulation and the calculation of theoretical model, the effectiveness of the new added mass calculation method and the accuracy of the water-exit dynamic model that considers the added mass changing rate are verified.
Źródło:
Polish Maritime Research; 2017, S 3; 152-164
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heave motion of a vertical cylinder with heave plates
Autorzy:
Ciba, Ewelina
Powiązania:
https://bibliotekanauki.pl/articles/1573695.pdf
Data publikacji:
2021
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
spar platforms
heave plates
damping coefficient
added mass coefficient
Opis:
The shape of a vertical cylinder resembles the classic form of a spar platform. Spar platforms are floating platforms that are successfully used in waters of great depths and have several advantages that mean they are readily used in the oil industry. Many of these advantages are also relevant to their application for offshore wind turbines, which is currently being considered. In the hydrodynamic analysis of spar platforms, the determination of their hydrodynamic coefficients plays an important role. They can be determined based on the free decay test. The study presents a method for determining the hydrodynamic coefficients of an object based on the free decay test. The results of free oscillation calculations with the help of numerical fluid mechanics tools are presented and compared with the results of the experiment and analytical solution. The application of determined coefficients and their significance for floating platforms are discussed. The influence of change in the form of an additional damping element on the behaviour of spar structures is shown.
Źródło:
Polish Maritime Research; 2021, 1; 42-47
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On hydrodynamic forces acting on the ship in large motions
Autorzy:
Błocki, W.
Powiązania:
https://bibliotekanauki.pl/articles/259385.pdf
Data publikacji:
2004
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
hydrodynamic forces
ship motions of large amplitudes
added forces
Opis:
Present stale of mathematical description of ship dynamic non-linear behaviour is preŹsented in this paper with a view to avoiding excessive complications in solving the proŹblem. The non-linearity concerns first of all Froude-Krilov forces and damping forces occurring after entering ship's deck into water or those resulting from drag of bilge keels. And, to the remaining, accompanying and diffraction forces the linear extrapolation has been applied.
Źródło:
Polish Maritime Research; 2004, 3; 7-10
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transfer function for a controllable pitch propeller with added water mass
Autorzy:
Leshchev, Volodimir
Maslov, Igor
Palagin, Oleksandr
Naydyonov, Andrii
Powiązania:
https://bibliotekanauki.pl/articles/34604683.pdf
Data publikacji:
2023
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
propulsion system
torsional vibrations
shaft line
added water mass
transfer function
propeller screw
Opis:
The relevance of this study lies in the fact that it presents a mathematical model of the dynamics of the propulsion system of a ship that takes into consideration the mass of water added to it. The influence of this phenomenon on the resonant frequencies of the propeller shaft is examined, and a transfer function for a controllable-pitch propeller is obtained for various operating modes. The purpose of the study is to improve the calculation of the dynamic operating modes of a controllable-pitch propeller by examining the features of a visual models. The VisSim software package is used in the study. A visual model is developed that considers the influence of the rotational speed on the value of the rotational inertia attached to the variable-pitch screw of the mass of water, and a special transfer function is proposed. The study shows that a transfer function of this type has a loop enabling negative feedback. An analysis of the operation of the propeller shaft at its resonant frequency is conducted based on the application of frequency characteristics using the transfer functions obtained. We show that in the low-frequency region, a consideration of the added rotational inertia using the proposed transfer function leads to a significant difference compared to the result obtained with the existing calculation method.
Źródło:
Polish Maritime Research; 2023, 4; 74-80
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determination of seakeeping performance for a case study vessel by the strip theory method
Autorzy:
Niklas, Karol
Karczewski, Artur
Powiązania:
https://bibliotekanauki.pl/articles/1573815.pdf
Data publikacji:
2020
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
ship design
seakeeping
ship motion
added resistance
towing tank
strip theory
Opis:
The increase of seakeeping performance is of particular importance for car and passenger ferries, service ships in the gas and oil extraction industry and offshore wind power farm industry, as well as for special purpose ships (including military applications). In the water areas of the Baltic Sea, North Sea, and Mediterranean Sea, which are characterised by a short and steep wave, the hull shape has a substantial impact on the operational capacity and propulsion efficiency of the ship, as well as on comfort and safety of navigation. The article analyses selected aspects of seakeeping for four variants of a selected case study vessel, indicating practical limitations of the strip method. The analysed aspects included hull heaving and pitching, added resistance, Motion Thickness Indicator (MSI), and Subjective Magnitude (SM). Experimental tests were also performed in the towing tank. Their comparison with the numerical results has indicated high inaccuracy of the strip method. What is more, the simplified representation of hull shape used in the strip method makes it impossible to analyse the effect of hull shape changes on the predicted seakeeping characteristics. Especially for the case of head wave, neglecting highly non-linear phenomena, such as slamming or head wave breaking, in strip method-based computer simulations will significantly decrease the reliability of the obtained results. When using the strip method, the seakeeping analysis should be complemented with model tests in a towing tank, or by another more complex numerical analysis, such as CFD for instance.
Źródło:
Polish Maritime Research; 2020, 4; 4-16
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fluid–structure interaction vibration experiments and numerical verification of a real marine propeller
Autorzy:
Lou, Benqiang
Cui, Hongyu
Powiązania:
https://bibliotekanauki.pl/articles/1955613.pdf
Data publikacji:
2021
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
fluid–structure interaction
real propeller vibration experiments
direct coupling
finite element method
added mass ratios
Opis:
The design of lifting blade shapes is a key engineering application, especially in domains such as those of marine propellers, hydrofoils, and tidal energy converters. In particular, the excitation frequency must be different from that of the structure to avoid resonance. The natural frequency in the cases where the fluid–structure interaction (FSI) is considerably different if considering the coupling added mass (AM) of the water. In this study, vibration experiments were performed using a real propeller in air and water. The modal parameters, natural frequencies, and mode shapes were determined. Validations were performed using 3D solid and acoustic elements in a direct coupling finite element format. The modal results and AM ratios were in agreement with the experimental results. Convenient application and high efficiency are basic requirements for an engineering application. Therefore, an empirical formula was established for the first-order FSI natural frequency to enable rapid estimation, thereby satisfying this requirement.
Źródło:
Polish Maritime Research; 2021, 3; 61-75
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Forced motion CFD simulation and load refinement evaluation of floating vertical-axis tidal current turbines
Autorzy:
Zhang, Wanchao
Zhou, Yujie
Wang, Kai
Zhou, Xiaoguo
Powiązania:
https://bibliotekanauki.pl/articles/1573876.pdf
Data publikacji:
2020
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
vertical-axis tidal current turbine
hydrodynamic loads
pitching motion
added mass
damping coefficients
Opis:
Simulation of the hydrodynamic performance of a floating current turbine in a combined wave and flow environment is important. In this paper, ANSYS-CFX software is used to analyse the hydrodynamic performance of a vertical-axis turbine with various influence factors such as tip speed ratio, pitching frequency and amplitude. Time-varying curves for thrust and lateral forces are fitted with the least squares method; the added mass and damping coefficients are refined to analyse the influence of the former factors. The simulation results demonstrate that, compared with nonpitching and rotating turbines under constant inflow, the time-varying load of rotating turbines with pitching exhibits an additional fluctuation. The pitching motion of the turbine has a positive effect on the power output. The fluctuation amplitudes of thrust and lateral force envelope curves have a positive correlation with the frequency and amplitude of the pitching motion and tip speed ratio, which is harmful to the turbine’s structural strength. The mean values of the forces are slightly affected by pitching frequencies and amplitudes, but positively proportional to the tip speed ratio of the turbine. Based upon the least squares method, the thrust and lateral force coefficients can be divided into three components, uniform load coefficient, added mass and damping coefficients, the middle one being significantly smaller than the other two. Damping force plays a more important role in the fluctuation of loads induced by pitching motion. These results can facilitate study of the motion response of floating vertical-axis tidal current turbine systems in waves.
Źródło:
Polish Maritime Research; 2020, 3; 40-49
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vessel energy requirement prediction from acceleration stage towing tests on scale models
Autorzy:
Wrzask, Klaudia
Powiązania:
https://bibliotekanauki.pl/articles/34604690.pdf
Data publikacji:
2023
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
ships energy requirement
towing tank test
acceleration stage
hydrodynamic added mass
Opis:
One of the most crucial tasks for naval architects is computing the energy required to meet the ship’s operational needs. When predicting a ship’s energy requirements, a series of hull resistance tests on a scale model vessel is carried out in constant speed stages, while the acceleration stage measurements are ignored. Another important factor in seakeeping analysis is the ship’s hydrodynamic added mass. The second law of dynamics states that all this valuable information, that is, the dependence of the hull resistance on the vessel’s speed and the added mass, is accessible from just one acceleration stage towing test done up to the maximum speed. Therefore, the acceleration stage, often overlooked in traditional towing experiments, can be a valuable source of information. For this reason, this work aims to generalise Froude’s scaling procedure to full-scale vessels for the accelerated stage towing tests.
Źródło:
Polish Maritime Research; 2023, 2; 4-10
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-11 z 11

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