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Modelling of the viscosity effect of heave plates for floating wind turbines by hydrodynamic coefficients

Ciba Ewelina, Dymarski Paweł

Acta Mechanica et Automatica

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2023

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Vol. 17, no. 3

469--476

EN

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.

2

Heave plates with holes for floating offshore wind turbines

Ciba Ewelina, Dymarski Paweł, Grygorowicz Mirosław

Polish Maritime Research

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2022

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nr 1

26--33

EN

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.

3

Analysis of the hydrodynamic properties of the 3-column Spar platform for offshore wind turbines

Ciba Ewelina, Dymarski Paweł, Grygorowicz Mirosław

Polish Maritime Research

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2022

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nr 2

35--42

EN

The article presents a design of a floating platform for offshore wind turbines. The concept is a modification of the Spar design and consists of three variable section columns connected to each other by a ballast tank in the lower part of the platform. This solution makes it possible to influence the position of the centre of buoyancy and the centre of mass of the structure. Compared to the classic Spar platform structure, the centre of buoyancy can be higher than mid-draft, which will provide the platform with greater stability. At the same time, this concept is better, in terms of technology, because of its modular structure and smaller bending radii.On the basis of the model testing performed, the hydrodynamic coefficients of the designed platform and its response to a given regular wave were determined (the transfer functions for heave and pitch motion were determined). Then, based on the damping coefficients, the platform was modelled in the ANSYS AQWA program and the results were very similar.

4

An innovative method of measuring the extension of the piston rod in hydraulic cylinders, especially large ones used in the shipbuilding and offshore industry

Dymarski Paweł, Dymarski Czesław, Grymajło Piotr

Polish Maritime Research

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2022

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nr 3

154--159

EN

The article presents the results of selected works related to the wider subject of research conducted at the Faculty of Mechanical Engineering and Shipbuilding at the Gdańsk University of Technology, regarding designing various on board devices with hydraulic drive for ships and other offshore facilities. One of the commonly used these mechanisms are hydraulic actuators with the measurement of the piston rod extension. The issue of precise measurement of the piston rod extension is extremely important in modern technologies of construction, assembly and precise displacement and positioning of large and heavy, both land and ocean engineering objects or structural elements with the use of several large hydraulic cylinders working in parallel. The article presents a one of two new patented P.425099 – A device for measuring the extension of a hydraulic cylinder piston rod. [1].

5

Stability analysis of the floating offshore wind turbine support structure of CELL SPAR type during its installation

Dymarski Paweł, Dymarski Czesław, Ciba Ewelina

Polish Maritime Research

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2019

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nr 4

109--116

EN

The article presents the results of selected works related to the wider subject of the research conducted at the Faculty of Ocean Engineering and Ship Technology of the Gdansk University of Technology, which concerns design and technology of construction, towing, and settlement on the seabed, or anchoring, of supporting structures for offshore wind farms. As a result of this research, several designs of this type of objects were developed, including two stationary types: gravitational and Jack-up, which are placed on the seabed, and two floating types: TLP and SPAR, anchored with tendons and anchors in the form of nailed or suction piles. Below presented is the stability analysis of the new floating CELL SPAR type support structure for offshore wind turbines during its installation in waters with a depth of over 65 m.

6

Design of jack-up platform for 6 MW WIND TURBINE: parametric analysis based dimensioning of platform legs

Dymarski Paweł

Polish Maritime Research

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2019

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nr 2

183--197

EN

The article presents the results of the research conducted within the framework of the project entitled WIND-TU-PLA (ERA-NET, MARTEC II), the general aim of which was to design and analyse supporting structures for wind turbines intended for operation on the South Baltic area. The research part described in the article aimed at developing a preliminary design for a jack-up platform which can operate on water areas with depth of 40 m. The main task was to determine optimal dimensions of platform legs and the radius of their spacing. Two jack-up platform concepts differing by spacing radius and hull dimensions were designed with the intention to be used as a supporting structure for a 6-MW offshore wind turbine. For each concept, the parametric analysis was performed to determine optimal dimensions of platform legs (diameter Dleg and plating thickness tleg). Relevant calculations were performed to assess the movements of the platform with parameters given in Table 1 in conditions simulating the action of the most violent storm in recent 50 years. The obtained results, having the form of amplitudes of selected physical quantities, are shown in comprehensive charts in Fig. 6 and 7. Based on the critical stress values (corresponding to the yield stress), the area was defined in which the impact strength conditions are satisfied (Fig. 14). Then, the fatigue strength analysis was performed for two selected critical leg nodes (Fig. 12). Its results were used for defining the acceptable area with respect to structure’s fatigue (Fig. 14). Geometric parameters were determined which meet the adopted criteria, Table 6. The decisive criterion turned out to be the fatigue strength criterion, while the yield point criterion appeared to be an inactive constraint.