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- ENERGY LOSSES IN FLOATING OFFSHORE WIND TURBINE WITH VARIABLE WIND
DIRECTION
Authors: Carlos Armenta-Déu, José Lomo
Pages: 1 - 16
Abstract: The paper analyses the effects of the variation of wind direction onto the performance of a floating offshore wind turbine (FOWT). The evolution of the Cp coefficient is developed as a function of the velocity of the yaw angle correction when realigning the FOWT after a wind direction change. The results are computed for velocities correction of the yaw angle between 1º/min and 5º/min. A maximum drop of the Cp coefficient of 7.4% has been found at the transient state. Simulation tests have been run over a period of 24 hours. The maximum drop value does not depend on the velocity correction of the yaw angle, but the elapsed time for the transitory state does, what affects the performance of the FOWT and the global power generation over a specific period. The loss of global power is inversely proportional to the velocity correction of the yaw angle, with a minimum loss of 0.83% for the case of 5º/min and a maximum loss of 4.16% for 5º/min. The absolute power loss in a marine turbine of 8 MW can reach values up to 0.33 MW. A quadratic dependence of energy loss on the yaw speed has been found within a 100% accuracy. The correlation shows there is a threshold value of 4º/min for the yaw speed beyond which absolute and relative energy losses maintain quite constant. This value is considered as the optimum value for the yaw speed to obtain maximum performance in the wind turbine.
PubDate: 2022-05-16
Issue No: Vol. 9, No. 1 (2022)
- A Note On Design Methodology For Sheet Pile In A River With Large Tidal
Variation
Authors: Parimal Bhattacharya
Pages: 17 - 33
Abstract: The stretch of river Ganges from Kolkata to Haldia port experiences high variation of tide and occasionally experiences remarkable phenomena of bore tides which take place under the right hydraulic and astronomical conditions. A tidal bore, consisting of the head-wave of an advancing tide, hemmed in where the estuary narrows suddenly into the river moves rapidly up the river at speeds reaching 10 m/s. Further, the rise of water depth may exceed 2m at specific locations depending upon local geometry and bathymetry. As a tidal bore surges up an estuary, it tends to lift up any floating matter, including vessels and jetties. If the rise is too high and sudden, the upward pull could be severe, often dislodging moorings of floating jetties. One such severe occurrences of a tidal bore in recent times took place on the 20th of September, 2014 when quite a few damages were reported. Under this environment with unpredictable natural phenomenon, it becomes difficult to design simple Sheet Pile barrier for completely block entry of water to shore side shipbuilding infrastructure like a Dry Dock for carrying out necessary repair to its gate. One such situation had arisen when a medium size shipyard located in Kolkata, India wanted to put up Sheet Pile barrier to carry out modernisation and install a new Gate in the existing Dry Dock. Two attempts to put up water tight barrier were unsuccessful as the high tide in the river slowly scoured away the underground soil with possible piping effect and the barriers collapsed. In the third attempt the author designed a sheet pile barrier considering all the possible forces posed by the river and the barrier is intact for two years since its installation. The present article describes in short the methodology applied, so that it can be replicated in similar situation. Keywords: Sheet Pile structure, Wave force, Scouring effect, Uplift Pressure and Exit gradient, Current Force, Wave Force, Hydrostatic Force, Soil Pressure.
PubDate: 2022-06-08
Issue No: Vol. 9, No. 1 (2022)
- A Literature Review on structural analysis and design of offshore
structure
Authors: Syed shafahaduddin quadri, R. M. Sawant
Pages: 34 - 36
Abstract: In the present give a review study on structural analysis and design of marine structures i.e. offshore structure. This review study deals with the structural geometry of compliant offshore platforms while emphasizing the design and development of these platforms rather than of fixed platforms. Investigations is carried out on the response control of a tension leg platform (TLP) and an articulated tower are presented. various control strategies that are commonly deployed for the response control of structures subjected to lateral forces while presenting detailed applications of tuned mass dampers (TMDs) in offshore structures. The modeling of offshore structures was carried out by using computer program i.e., SAP, STAAD, ANSYS, MATLAB and SAC. The investigation is carryout by considering different parameters like offshore structure, Compliant platforms, Floating platforms, articulated towers, tension leg platform (TLPs). Key Words: offshore structure, Compliant platforms, Floating platforms, articulated towers, tension leg platform (TLPs).
PubDate: 2022-06-08
Issue No: Vol. 9, No. 1 (2022)
- EFFICIENCY INCREASE IN MARINE WIND TURBINES
Authors: Carlos Armenta-Déu
Pages: 37 - 49
Abstract: The paper studies a method to increase the efficiency in floating marine wind turbines by modifying the pitch angle of the wind rotor blades to make the wind turbine operating at optimum conditions. The pitch angle is adjusted to its optimum value as a function of the tilt angle of the wind turbine mast when submitted to the wave movement. The analysis of the situation has led to a theoretical model that predicts the best pitch angle depending on the angle of attack of the wind. A mechanism to compensate the variation of the pitch angle due to the oscillation of the wind turbine is proposed, therefore, the maximum output power is reached under specific working conditions.
PubDate: 2022-06-08
Issue No: Vol. 9, No. 1 (2022)
- Analytically and Numerically Predicting Base Shear Coefficient of Building
Structure with the Variations of Response Reduction Factor based on BNBC
2020 by using ETABS
Authors: Md. Foisal Haque
Pages: 50 - 55
Abstract: Response reduction factor (RRF) influences the building base shear. Soil profile and seismic
zone factors affect the variations of RRF. According to Bangladesh National Building Code
(BNBC 2020), three (ordinary, intermediate, and special) different values of RRF for the
moment-resisting frame are used for four seismic zones. In the present research, analytical
(BNBC 2020) and numerical (ETABS) base shear coefficient ratio (BSC) are evaluated by
the variations of RRF (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12) and seismic zoning factors (Z 1 =
0.12, Z 2 = 0.20, Z 3 = 0.28 and Z 4 = 0.36). BSC values are very close for analytical and
numerical analysis. The maximum value of analytical and numerical base shear coefficient
ratio (BSCR) is 100.29 percent for seismic zone – 1 (RRF = 7). Similarly, the minimum value
of BSCR is 99.97 percent for seismic zone -1 (RRF = 10). For all values of RRF and seismic
zone factors, numerical BSC is lower than analytical BSC except the location of minimum
BSCR.
KEYWORDS: Base shear coefficient, Response reduction factor, Analytical formulae,
BNBC 2020, Numerical analysis.
PubDate: 2022-06-08
Issue No: Vol. 9, No. 1 (2022)
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