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Wyszukujesz frazę "coefficients" wg kryterium: Temat


Wyświetlanie 1-9 z 9
Tytuł:
The experimental identification of the dynamic coefficients of two hydrodynamic journal bearings operating at constant rotational speed and under nonlinear conditions
Autorzy:
Breńkacz, Ł.
Żywica, G.
Drosińska-Komor, M.
Powiązania:
https://bibliotekanauki.pl/articles/259675.pdf
Data publikacji:
2017
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
bearing dynamic coefficients
experimental research
nonlinear coefficients
impact excitation
hydrodynamic bearing
Opis:
Hydrodynamic bearings are commonly used in ship propulsion systems. Typically, they are calculated using numerical or experimental methods. This paper presents an experimental study through which it has been possible to estimate 24 dynamic coefficients of two hydrodynamic slide bearings operating under nonlinear conditions. During the investigation, bearing mass coefficients are identified by means of a newly developed algorithm. An impact hammer was used to excite vibration of the shaft. The approximation by means of the least squares method was applied to determine bearing dynamic coefficients. Based on the performed research, the four (i.e. two main and two crosscoupled) coefficients of stiffness, damping and mass for each bearing were obtained. The mass coefficients add up to the complex shaft weight. These values are not required for modeling dynamics of the machine because the rotor mass is usually known, however, they may serve as a good indicator to validate the correctness of the stiffness and damping coefficients determined. Additionally, the experimental research procedure was described. The signals of displacements in the bearings and the excitation forces used for determination of the bearing dynamic coefficients were shown. The study discussed in this article is about a rotor supported by two hydrodynamic bearings operating in a nonlinear manner. On the basis of computations, the results of bearing dynamic coefficients were presented for a selected speed.
Źródło:
Polish Maritime Research; 2017, 4; 108-115
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Latitude error in compass deviation. Mathematical method to determine the latitude error in magnetic compass deviation
Autorzy:
Basterretxea, I. I.
Vila- Muñoz, J. A.
Perez -Labajos, C. A.
Powiązania:
https://bibliotekanauki.pl/articles/258974.pdf
Data publikacji:
2014
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
optimal exact coefficients
average deviation
latitude error
Opis:
This article aims to provide the seafarer with a tool to calculate the deviation for a righted ship in any geographical position using only the information available on board. In this way the accidental errors in the deviation card are reduced and the latitude error is made negligible. Moreover, an experimental application of this method is carried out on board a tanker to compare the latitude error in different positions at sea.
Źródło:
Polish Maritime Research; 2014, 3; 25-31
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Estimation of hydrodynamic coefficients from results of real ship sea trials
Autorzy:
Kim, D.
Powiązania:
https://bibliotekanauki.pl/articles/260199.pdf
Data publikacji:
2018
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
ship manoeuvrability
system identification method
hydrodynamic coefficients
sea trials
mathematical optimization
Opis:
This paper suggests an estimation method for ship’s hydrodynamic coefficients, which is based on the system identification method that calculates an optimum value in a mathematical way. For the purpose of modelling existing ships, this study collects real ship sea trial data as benchmarks. Prior to the optimization, a sensitivity analysis is carried out for easy and effective optimization. The simulation results using optimized coefficients agree well with corresponding benchmarks. Following this, with various trim and draught conditions, this study suggests new estimation formulas that concern all trim and draught conditions. Simulation results applying the estimation formulas are satisfactory in regard to a corresponding benchmark, compared to a result obtained by using an existing regression formula.
Źródło:
Polish Maritime Research; 2018, 4; 65-72
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Energy loss coefficients ki in a displacement pump and hydraulic motor used in hydrostatic drives
Autorzy:
Maczyszyn, Agnieszka
Powiązania:
https://bibliotekanauki.pl/articles/259211.pdf
Data publikacji:
2019
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
hydrostatic drive
energy loss rate
pump
hydraulic motor
energy loss coefficients
Opis:
The article aims at defining and analysing the energy loss coefficients in design solutions of rotating displacement machines, with a piston machine as an example. The energy losses observed in these machines include mechanical loss, volumetric loss, and pressure loss. The scale and relations between these losses in different machines depend on machine design and manufacturing quality, and on operating parameters. The operating parameters, in turn, which affect directly or indirectly the above losses depend on whether the machine works in pump or hydraulic motor regime. The article is also a contribution to the development of a library of ki coefficients which define the losses in displacement machines, as the knowledge about these coefficients makes it possible to assess fast and easily the energy efficiency of a machine or drive system at each point of its working area.
Źródło:
Polish Maritime Research; 2019, 3; 47-55
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Methodology of assessing the production capacity of selected shipyards
Autorzy:
Pyszko, R.
Powiązania:
https://bibliotekanauki.pl/articles/962793.pdf
Data publikacji:
2004
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
sttructural and production process coefficients
index method
labour demand
worstand - hours (Stg)
Opis:
The paper deals with selected subjects in the European EUREKA "Baltecologicalship" 'E!2772 project. Within the project, preliminary designs offour feeder (short shipping) ships have been developed based on the market trend research, design knowledge and experimental investigations. The following tasks were to be performed for one of the ships: defi ning optimum building conditions (timescale, production technologies, ecological aspect), selecting shipyards meeting the minimum production capacity requirement. For that purpose an index method was developed (based on the design and production indices). Then an index analysis was performed of the production capacities of selected shipyards (and also different configurations of cooperation between them) and results were presented in a form of the Gantt diagrams. Final conclusions were drawn.
Źródło:
Polish Maritime Research; 2004, S 1; 24-28
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:
Numerical investigation of the hydrodynamic performance of the propeller behind the ship with and without WED
Autorzy:
Nadery, Alireza
Ghassemi, Hassan
Powiązania:
https://bibliotekanauki.pl/articles/1573802.pdf
Data publikacji:
2020
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
ship propeller
wake equalizing duct
hydrodynamic coefficients
Taguchi design of experiment
delivered power
Opis:
The presented paper numerically carries out the investigation of the hydrodynamic performance of the propeller behind the ship with and without wake equalizing duct (WED). It is mounted in front of the propeller in order to equalize the ship’s wake flow and improve the propeller performance. The computational fluid dynamics (CFD) analysis software STAR-CCM solver was adopted to simulate the KP505 propeller behind the KRISO container ship (KCS) using overlapping grid technology and user-defined functions. To obtain the effect of a –duct on propeller performance, the ship bare hull case, the with-propeller case, and the with-propeller-and-duct case are also computed. Together, these computations provide for a –complete CFD comparison of the duct effects. Also, the Taguchi design of the experiment method is applied to investigate three parameters (angle of attack, trailing edge radius, and chord length) of the duct. Finally, the main dimensions are obtained, and the thrust and torque coefficients are presented and discussed for one blade and whole blades during one cycle. Based on the numerical results, it is indicated that good design increases efficiency by 1.67%, and a –bad design may reduce efficiency by 3.25%. Also, the effect of the WED caused to decrease the pressure pulse by 35.9% in the face side of the propeller blade.
Źródło:
Polish Maritime Research; 2020, 4; 50-59
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effective method for determining environmental loads on supporting structures for offshore wind turbines
Autorzy:
Dymarski, P.
Ciba, E.
Marcinkowski, T.
Powiązania:
https://bibliotekanauki.pl/articles/258490.pdf
Data publikacji:
2016
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
offshore wind turbine
support structure
Morison force coefficients
CFD
sea wave statistics
Baltic Sea
Opis:
This paper presents a description of an effective method for determining loads due to waves and current acting on the supporting structures of the offshore wind turbines. This method is dedicated to the structures consisting of the cylindrical or conical elements as well as (truncates) pyramids of polygon with a large number of sides (8 or more). The presented computational method is based on the Morison equation, which was originally developed only for cylindrically shaped structures. The new algorithm shown here uses the coefficients of inertia and drag forces that were calculated for non-cylindrical shapes. The analysed structure consists of segments which are truncated pyramids on the basis of a hex decagon. The inertia coefficients, CM, and drag coefficients, CD, were determined using RANSE-CFD calculations. The CFD simulations were performed for a specific range of variation of the period, and for a certain range of amplitudes of the velocity. In addition, the analysis of influence of the surface roughness on the inertia and drag coefficients was performed. In the next step, the computations of sea wave, current and wind load on supporting structure for the fifty-year storm were carried out. The simulations were performed in the time domain and as a result the function of forces distribution along the construction elements was obtained. The most unfavourable distribution of forces will be used, to analyse the strength of the structure, as the design load.
Źródło:
Polish Maritime Research; 2016, 1; 52-60
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The disturbances of the life raft leeway induced by the fluctuations of wind direction in the life raft coordinate system
Autorzy:
Burciu, Z.
Powiązania:
https://bibliotekanauki.pl/articles/260580.pdf
Data publikacji:
2007
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
search and rescue
life raft aerodynamic coefficients
sea investigations of life raft leeway
model of life raft leeway
Opis:
The paper presents the results of investigations on the life raft leeway induced by the fluctuations of wind direction. The surface current is one of the main factors determining the life raft leeway, but the recently conducted research confirmed that there are also other elements influencing the perturbations of leeway direction. The field experiments showed diversion of the life raft leeway from the downwind direction. This diversion can be explained by the existing cross wind component. The wind tunnel tests allowed to determine the aerodynamic coefficients in the fluid-state control system. On the basis of the test results the expression for the wind pressure force has been formulated. The mean deviation and median of probability distribution of the leeway diversions from the downwind direction has been determined on the basis of investigations conducted at sea. The models for the life raft velocity dependent on wind velocity, developed for the life raft with drogue and without drogue, are presented in the paper.
Źródło:
Polish Maritime Research; 2007, S 2; 60-63
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-9 z 9

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