The impact of the seabed morphology on turbulence generation in a strong tidal stream

2021 ◽  
Vol 33 (5) ◽  
pp. 055125
Author(s):  
Philippe Mercier ◽  
Sylvain Guillou
Keyword(s):  
Tidal Stream ◽  
Turbulence Generation ◽  
The Impact

Navigation on the Thames

1972 ◽  
Vol 272 (1221) ◽  
pp. 201-212
Keyword(s):  
Deep Sea ◽  
Flood Control ◽  
Working Party ◽  
Maximum Size ◽  
Flood Protection ◽  
Precise Timing ◽  
Flood Level ◽  
Bulk Carriers ◽  
Tidal Stream ◽  
The Impact

The tidal Thames is flanked by a complex of industrial terminals and dock entrances which are used by a wide variety of vessels, ranging from deep-sea bulk carriers to tugs handling strings of barges. One of the biggest growth trades is oil, the inland distribution of which is by tank barge. There is a variation of the pattern of movement governed both by the tide and commercial considerations. Navigation on the river will be affected by the size of opening since the level of movement needs the widest possible channel and for preference any constriction should be as far up river as practicable. Allied with this requirement is the need for maximum size of opening and the 61m proposed, while adequate, introduces limitations, particularly for the larger vessel. During construction, special arrangements for navigation will be required to ensure the minimum of disruption to traffic both transitting the area and using terminals in the vicinity of the barrier site. The closure of the barrier will halt all vessels bound through it and is likely to delay them for up to 12 h. It will also have some effect on vessels bound for docks below the barrier. Special arrangements will be required to enable all such vessels to wait. Running costs of vessels likely to be delayed range from £1500 to £300 per day and so the overall sum could be high. Membership of the Navigational Working Party includes representation from all concerned with the movement of vessels on the river. Their initial deliberations were to conclude which site would be acceptable and whilst factors other than navigational had also to be considered, acceptance of the Woolwich site was governed by the forecast of the likely rate of closures to be initially no more than 2 per annum. With opening widths of 61 m, a long straight approach is needed to ensure ease of navigation and the piers of the barrier must be alined to the direction of the tidal stream. T o minimize disruption of navigation, the level of the sill must be low enough to ensure that vessels are not hindered. Sill level also needs to be considered in relation to the regime of the river. Use of the barrier other than for flood control could create problems of siltation and pollution and it is essential before using the barrier for other than its prime purpose to establish that there is no such possibility. Arrangements for control of navigation remain to be finalized, but special signals, radio, visual and aural will be required. Also requiring further consideration is the precise timing of closures. Because of the vital need to prevent flooding, the number of closures may exceed the forecast. This is apparent from experience to date and the tidal pattern of initially indicating a surge which subsequently does not reach flood level. While economic pressures have resulted in a design not necessarily ideal from navigational considerations, it is hoped that the Working Party’s deliberations can minimize the impact on the trade of the Port while ensuring flood protection to London.

scholarly journals Lifetime Analysis of IGBT Power Modules in Passively Cooled Tidal Turbine Converters

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1875
Author(s):  
Faisal Wani ◽  
Udai Shipurkar ◽  
Jianning Dong ◽  
Henk Polinder ◽  
Antonio Jarquin-Laguna ◽  
...  
Keyword(s):  
Thermal Cycling ◽  
Surface Waves ◽  
Stream Velocity ◽  
Insulated Gate Bipolar Transistor ◽  
Cost Of Energy ◽  
Igbt Modules ◽  
Lifetime Analysis ◽  
Tidal Turbine ◽  
Tidal Stream ◽  
The Impact

Thermal cycling is one of the major reasons for failure in power electronic converters. For submerged tidal turbine converters investigating this failure mode is critical in improving the reliability, and minimizing the cost of energy from tidal turbines. This paper considers a submerged tidal turbine converter which is passively cooled by seawater, and where the turbine has fixed-pitch blades. In this respect, this study is different from similar studies on wind turbine converters, which are mostly cooled by active methods, and where turbines are mostly pitch controlled. The main goal is to quantify the impact of surface waves and turbulence in tidal stream velocity on the lifetime of the converter IGBT (insulated gate bipolar transistor) modules. The lifetime model of the IGBT modules is based on the accumulation of fatigue due to thermal cycling. Results indicate that turbulence and surface waves can have a significant impact on the lifetime of the IGBT modules. Furthermore, to accelerate the speed of the lifetime calculation, this paper uses a modified approach by dividing the thermal models into low and high frequency models. The final calculated lifetime values suggest that relying on passive cooling could be adequate for the tidal converters as far as thermal cycling is concerned.

The impact of spring-neap tidal-stream cycles in tidal energy assessments in the Chilean Inland Sea

2019 ◽  
Vol 139 ◽  
pp. 496-506 ◽  
Author(s):  
Osvaldo Artal ◽  
Oscar Pizarro ◽  
Héctor H. Sepúlveda
Keyword(s):  
Tidal Energy ◽  
Tidal Stream ◽  
The Impact

The impact of tidal stream turbines on large-scale sediment dynamics

2009 ◽  
Vol 34 (12) ◽  
pp. 2803-2812 ◽  
Author(s):  
Simon P. Neill ◽  
Emmer J. Litt ◽  
Scott J. Couch ◽  
Alan G. Davies
Keyword(s):  
Large Scale ◽  
Sediment Dynamics ◽  
Tidal Stream ◽  
The Impact

Combined Wave-Current-Turbulent Flow Environments Generation for Tidal Turbine Design

2020 ◽  
Author(s):  
Qian Li ◽  
Venugopal Vengatesan ◽  
Nigel Barltrop
Keyword(s):  
Turbulent Flow ◽  
Systematic Investigation ◽  
Current Configuration ◽  
Irregular Wave ◽  
Wave Kinematics ◽  
Tidal Turbine ◽  
Tidal Stream ◽  
Ambient Turbulence ◽  
Turbine Design ◽  
The Impact

Abstract In this paper, a methodology to generate combined wave, tidal current and turbulent flow environment for application to determining hydrodynamic loading on a horizontal axis Tidal Stream Turbine (TST) is proposed. A systematic investigation has been conducted within the framework of OpenFAST software suite. Necessary modifications in OpenFAST tool is made to simulate the hydrodynamics of the TST under combined wave-current-turbulence conditions. The modified software will be able to generate the inflow conditions for the TST accounting for the regular and irregular wave and current interactions, and, involve the impact of ambient turbulence on the loadings of TST. The modified algorithm is validated by comparing the numerical results with experimental test data and other numerical simulation results. Good agreements are achieved for both regular and irregular wave kinematics in time-domain and flow velocity/elevation spectra in the frequency domain. Also, each of the wave-current configuration has been tested with different turbulence intensities. The results suggests that the wave kinematics is greatly altered when waves propagating on currents and wave travelling on the following and opposing directions current shows remarkably different characteristics in relation to wave amplitude and frequency. It is also found that combined wave-current flow with different turbulence levels have strong correlations with the flow properties which is important for TST fatigue prediction. All the conclusions emphasis the fact that proper wave-current-turbulence interactions should be included in TST modelling.

scholarly journals Vessel Trajectory Analysis in Designated Harbor Route Considering the Influence of External Forces

2020 ◽  
Vol 8 (11) ◽  
pp. 860
Author(s):  
Ho Namgung ◽  
Joo-Sung Kim
Keyword(s):  
Support Vector ◽  
Optimal Parameters ◽  
Position Data ◽  
Tidal Stream ◽  
Ship Tracks ◽  
External Forces ◽  
Marine Accidents ◽  
The Impact ◽  
Track Monitoring ◽  
Fold Cross Validation

A vessel must navigate along designated routes within a harbor area to ensure navigation safety. The impact of strong currents is one of the most dangerous factors in coastal navigation. However, it is challenging to determine the deviation of a ship in advance from the ship’s position data in the case of a marine accident. In this study, to support the decision-making of ship navigators and vessel traffic service (VTS) operators in track monitoring tasks, tracks were classified according to the tidal stream, and the track distribution was analyzed according to the tidal current situations. Marine accident analysis was performed to investigate the tidal influence on ship tracks. Track data were collected for 12 months from a VTS center in Korea, and tidal information was collected through a meteorological observation buoy. Representative tracks were extracted from the track data using the support vector regression (SVR) seaway model. K-fold cross-validation and a grid search were performed to determine the optimal parameters. The ship tracks appeared in specific patterns according to the forces and directions of tidal currents, and specific deviation patterns were observed. This study is expected to contribute to the reduction of marine accidents by predicting ship trajectories according to the tidal situations in advance.

scholarly journals The impact of seabed rock roughness on tidal stream power extraction

Energy ◽  
2016 ◽  
Vol 112 ◽  
pp. 762-773 ◽  
Author(s):  
Nicolas Guillou ◽  
Jérôme Thiébot
Keyword(s):  
Stream Power ◽  
Power Extraction ◽  
Tidal Stream ◽  
The Impact ◽  
Tidal Stream Power
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