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Wyszukujesz frazę "heave" wg kryterium: Temat


Tytuł:
Utilization of an active and/or passive heave compensation in the equipment of dynamic positioning vessels
Autorzy:
Herdzik, J.
Tematy:
heave compensation
DP systems
passive heave compensation
active heave compensation
Pokaż więcej
Wydawca:
Instytut Techniczny Wojsk Lotniczych
Powiązania:
https://bibliotekanauki.pl/articles/241528.pdf  Link otwiera się w nowym oknie
Opis:
DP vessels have a possibility to maintain their position or heading by using thrusters and propellers but the heave compensation is not possible that way. Heave compensation is a technique used to reduce the influence of waves on a hull or only a part of an equipment inside the hull. There are two types of heave compensation: passive (PHC) and active (AHC). Due to limit, the energy demand the hybrid heave compensation (HHC) is often in use. The offshore activities needed the compensation to some extend (level) could be drilling, handling loads in cranes or pipe laying. Different types of Heave Compensator Systems (HCS) are used to compensate for these movements. Safety of these offshore activities is so important that the area of power (using external energy) and non-power (using only the energy of wave movement) drives are quickly developed. The heave compensators allow increasing the weather window and better making use of the offshore vessels. The expected level of decreasing the vessel heave in compare to work equipment is from 5 to 50 times. Active compensation by hydraulic motor needs its active run for motion compensation and the system ought to be equipped with accelerometer senses of ship movement. Computing algorithms and the choice of control method are principal in HCS performance. In the article, it was shown examples of different types of compensators with their advantages and disadvantages and their utilization.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Prediction of Heave from the CLOD Index for Natural and Contaminated Clay Soils from the Mazovia Area
Autorzy:
Wójcik, Emilia
Izdebska-Mucha, Dorota
Opis:
This paper deals with the prediction of free heave in expansive soils from central Poland. Thirty-nine soil samples differing in plasticity were selected for a comparative analysis. The soil types examined – Neogene clays, alluvial soils and glacial tills, differ in the CLOD index (Cw) values which range from 0.027 to 0.019, values for undisturbed samples being higher than those for the remoulded ones. The variability of the Cw index correlates best with the sand to clay ratio. Studies of soils contaminated with diesel oil (ON) have revealed that the Cw index decreases with the growing ON content. Calculations of the potential heave, assuming a 1% moisture change for a 1 m thick soil layer, show the heave to be 18 to 12 mm and 15 to 11 mm for Neogene clays and glacial tills respectively, depending on the in situ void ratio. Petroleum contamination significantly reduces the potential heave of the soil. The present analysis clearly suggests that glacial tills are more susceptible to oil-derived contamination than Neogene clays.
Dostawca treści:
Repozytorium Centrum Otwartej Nauki
Artykuł
Tytuł:
Heave analysis of shallow foundations founded in swelling clayey soil at N’Gaous city in Algeria
Autorzy:
Khennouf, Abdelaziz
Baheddi, Mohamed
Tematy:
clayey soil
swelling
analytical approach
foundation heave
numerical modelling
Pokaż więcej
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:
https://bibliotekanauki.pl/articles/1845129.pdf  Link otwiera się w nowym oknie
Opis:
The design of shallow foundations on swelling soils needs a thorough study to evaluate the effect of swelling potential soil on the final foundation heave. For this reason, a simple analytical approach based on the soil stress state under the foundation can be used to calculate the foundation heave. This paper reports a set of analytical and numerical analysis using the finite-difference code (FLAC 3D), performed on an isolated shallow foundation founded on a swelling soil mass at N’Gaous city in Batna Province, Algeria, subjected to distributed vertical loads. Further, the influence of some parameters on total heave was analyzed, such as the embedded foundation and soil stiffness. The analysis results from the proposed 3D modelling was compared and discussed with analytical results. The numerical results obtained show a good agreement with the analytical solutions based on oedometer tests proposed in the literature, and deliver a satisfactory prediction of the heave of the shallow foundations.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heave motion of a vertical cylinder with heave plates
Autorzy:
Ciba, Ewelina
Tematy:
spar platforms
heave plates
damping coefficient
added mass coefficient
Pokaż więcej
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:
https://bibliotekanauki.pl/articles/1573695.pdf  Link otwiera się w nowym oknie
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.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Opportunistic maintenance strategy of a Heave Compensation System for expected performance degradation
Autorzy:
Zhang, Chao
Qian, Yujie
Dui, Hongyan
Wang, Shaoping
Chen, Rentong
Tomovic, Mileta M.
Tematy:
opportunistic maintenance
importance measure
heave compensation
hydraulic system
Monte Carlo
Pokaż więcej
Wydawca:
Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Powiązania:
https://bibliotekanauki.pl/articles/2038156.pdf  Link otwiera się w nowym oknie
Opis:
In the marine industry, heave compensation systems are applied to marine equipment to compensate for the adverse effects of waves and the hydraulic system is usually used as the power system of heave compensation systems. This article introduces importance theory to the opportunistic maintenance (OM) strategy to provide guidance for the maintenance of heave compensation systems. The working principle of a semi-active heave compensation system and the specific working states of its hydraulic components are also first explained. Opportunistic maintenance is applied to the semi-active heave compensation system. Moreover, the joint integrated importance measure (JIIM) between different components at different moments is analyzed and used as the basis for the selection of components on which to perform PM, with the ultimate goal of delaying the degradation of the expected performance of the system. Finally, compared with conditional marginal reliability importance (CMRI)based OM, the effectiveness of JIIM-based OM is verified by the Monte Carlo method.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evaluation of expansivity of Neogene clays and glacial tills from cental Poland (Warszawa area) on the basis of suction tests
Autorzy:
Wójcik, Emilia
Izdebska-Mucha, Dorota
Wydawca:
Polish Geological Institute - National Research Institute
Opis:
This paper presents the characteristics of the expansivity and quantitative prediction of heave of clay soils from Poland based on suction testing. Eleven Neogene clays and six glacial tills, differing in genesis and plasticity, were analysed to identify the expansive potential using eight empirical methods. The laboratory studies included measurements of soil-water characteristic curves and soil index properties. Data from water content, volume and suction measurements served to determine the suction compression index Ch and the suction-water content index delta h/delta w of the soils examined. The values of these indices are clearly dependent on the clay fraction content in tested soils. Compared with glacial tills, Neogene clays are expected to exhibit greater changes in volume due to changes in soil suction. Comparative results of the evaluation of expansivity suggest that the chosen classification methodologies provided consistent expansion ratings for glacial tills, while the values for Neogene clays vary from low to very high. The lowest expansivity classes have been obtained from evaluation based on soil suction. The McKeen (1992) method has been adopted for calculations of the potential field heave of Neogene clays and glacial tills. In order to provide a rational estimation of expansive soil behavior, specialists should take into consideration the specific site and design features.
Dostawca treści:
Repozytorium Centrum Otwartej Nauki
Artykuł
Tytuł:
Evaluation of expansivity of Neogene clays and glacial tills from central Poland on the basis of suction tests
Autorzy:
Izdebska-Mucha, D.
Wójcik, E.
Tematy:
expansive soil
neogene clays
glacial tills
suction
suction compression index
heave
Pokaż więcej
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Powiązania:
https://bibliotekanauki.pl/articles/2059660.pdf  Link otwiera się w nowym oknie
Opis:
This paper presents the characteristics of the expansivity and quantitative prediction of heave of clay soils from Poland based on suction testing. 11 Neogene clays and 6 glacial tills, differing in genesis and plasticity, were analyzed to identify the expansive potential using eight empirical methods. The laboratory studies included measurements of soil-water characteristic curves and soil index properties. Data from water content, volume and suction measurements served to determine the suction compression index Ch and the suction-water content index Dh/Dw of the soils examined. The values of these indices are clearly dependent of the clay fraction content in tested soils. Compared with glacial tills, Neogene clays are expected to exhibit larger changes in volume due to changes in soil suction. Comparative results of the evaluation of expansivity suggest that the chosen classification methodologies provided consistent expansion ratings for glacial tills, while values for Neogene clays vary from low to very high. The lowest expansivity classes have been obtained from evaluation based on soil suction. The McKeen (1992) method has been adopted for calculations of the potential field heave of Neogene clays and glacial tills. In order to provide a rational estimation of expansive soil behavior, specialists should take into consideration the specific site and design features.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelling of the viscosity effect of heave plates for floating wind turbines by hydrodynamic coefficients
Autorzy:
Ciba, Ewelina
Dymarski, Paweł
Tematy:
spar platforms
heave plates
hydrodynamic coefficient
floating offshore wind turbine
FOWTs
Pokaż więcej
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Powiązania:
https://bibliotekanauki.pl/articles/2233713.pdf  Link otwiera się w nowym oknie
Opis:
One of the methods of modelling the movement of floating wind turbines is the use of the diffraction method. However, this method does not take into account the influence of viscosity; therefore, in many cases, it needs to be extended with a matrix of appropriate coefficients. The effect of viscosity causes both the added mass coefficient and the damping coefficient to increase. The determined coefficients were entered into the ANSYS AQWA program, and the calculation results of the transfer function determined with the use of linear and quadratic damping were presented. The results were compared with the results of the experiment, indicating greater convergence for the quadratic model.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heave plates with holes for floating offshore wind turbines
Autorzy:
Ciba, Ewelina
Dymarski, Paweł
Grygorowicz, Mirosław
Tematy:
spar platforms
heave plates
damping coefficient
Floating Offshore Wind Turbines (FOWTs)
Pokaż więcej
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:
https://bibliotekanauki.pl/articles/32891488.pdf  Link otwiera się w nowym oknie
Opis:
The paper presents an innovative solution which is heave plates with holes. The long-known heave plates are designed to damp the heave motion of platforms. They are most often used for Spar platforms. The growing interest in this type of platform as supporting structures for offshore wind turbines makes it necessary to look for new solutions. Based on the available literature and the authors’ own research, it was concluded that the main element responsible for the damping of heave plates is not so much the surface of the plate, but its edge. Therefore, it was decided to investigate the effect of the holes in heave plates on their damping coefficient. Model tests and CFD calculations were performed for three different structures: a smooth cylinder, a cylinder with heave plates with a diameter of 1.4 times the diameter of the cylinder, and a cylinder with the same plate, in which 24 holes were cut (Fig. 1). Free Decay Tests (FDT) were used to determine the damping coefficient and the natural period of heave, and then the values obtained were compared. The full and punched heave-plate designs were also tested with regular waves of different periods to obtain amplitude characteristics. The results obtained are not unequivocal, as a complex motion appears here; however, it is possible to clearly define the area in which the damping of a plate with holes is greater than that of a full plate.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on the influence of chamfer perforation on heave and pitch of a single floating platform
Autorzy:
Wang, Wei
Fan, Sheming
You, Yunxiang
Zhao, Cheng
Xu, Liqun
Wang, Guibiao
Lu, Zhiqiang
Tematy:
single floating wind power platform
different chamfered perforation
numerical simulation
experiment
heave plate
Pokaż więcej
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:
https://bibliotekanauki.pl/articles/32915201.pdf  Link otwiera się w nowym oknie
Opis:
The aim of this work is to study the influence of chamfered perforation and chamfering on the heave and pitch motion of a single floating wind power platform with an anti-heave device. Firstly, the hydrodynamic performance of a single floating body with different chamfers, or without perforation, is calculated and analysed. Secondly, the motion of a model without perforation and with 35° chamfered perforation is captured and studied in a towing tank. The results show that when the wave height is large and the period is small, the perforated device has a certain effect. When the wave height and period are small, the pitch suppression effect of chamfered perforation is more obvious than that of non-chamfered perforation. When the period and wave height are large, the heave suppression effect of non-chamfered perforation is better than that of chamfered perforation. In experimental research, the perforated floating body has a certain effect on restraining the heave and pitch of a floating body under most working conditions, and the effect of restraining the pitch is obviously better than that of restraining the heave.
Dostawca treści:
Biblioteka Nauki
Artykuł

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