scholarly journals Towards a turbulence characterization in tidal energy sites. First results of THYMOTE project

2019 ◽  
Vol 261 ◽  
pp. 05002 ◽  
Author(s):  
Sylvain Guillou ◽  
Jean-François Filipot ◽  
Jérôme Thiébot ◽  
Grégory Germain ◽  
Nicolas Chaplain ◽  
...  
Keyword(s):  
Free Surface ◽  
Numerical Modelling ◽  
Physical Modelling ◽  
Field Measurements ◽  
Tidal Energy ◽  
Turbulence Level ◽  
High Current ◽  
First Results ◽  
Tidal Turbine ◽  
High Turbulence

Tidal turbine will be installed in area with high current and high turbulence level. A characterisation of this last is required. The aim of the project THYMOTE is to characterize and understand the generation of eddies from smaller to several tens of meters. Three technics are used: Numerical modelling, Physical modelling, field measurements. Physical and numerical modelling show clearly the appearance of the eddies close to the bottom in presence of dunes or rocks and their motion towards the free surface.

scholarly journals Review of tidal turbine wake modelling methods

2020 ◽  
Vol 3 (2) ◽  
pp. 91-100
Author(s):  
Ellen Jump ◽  
Alasdair Macleod ◽  
Tom Wills
Keyword(s):  
Physical Modelling ◽  
Tidal Energy ◽  
Horizon 2020 ◽  
Wake Interactions ◽  
Tidal Turbine ◽  
Modelling Techniques ◽  
Turbine Wake ◽  
Modelling Methods ◽  
Optimal Site ◽  
Device Modelling

Enabling Future Arrays in Tidal (EnFAIT) is an EU Horizon 2020 flagship tidal energy project. It aims to demonstrate the development, operation and decommissioning of the world’s largest tidal array (six turbines), over a five-year period, to prove a cost reduction pathway for tidal energy and confirm that it can be cost competitive with other forms of renewable energy. To determine the optimal site layout and spacing between turbines within a tidal array, it is essential to accurately characterise tidal turbine wakes and their effects. This paper presents a state-of-the-art review of tidal turbine wake modelling methods, with an overview of the relevant fundamental theories. Numerical and physical modelling research completed by both academia and industry are considered to provide an overview of the contemporary understanding in this area. The scalability of single device modelling techniques to an array situation is discussed, particularly with respect to wake interactions.

scholarly journals The Effects of Surface Waves and Submergence on the Performance and Loading of a Tidal Turbine

2017 ◽  
Author(s):  
Xiaoxian Guo ◽  
Zhen Gao ◽  
Jianmin Yang ◽  
Torgeir Moan ◽  
Haining Lu ◽  
...  
Keyword(s):  
Free Surface ◽  
Surface Waves ◽  
Tidal Energy ◽  
High Energy ◽  
High Energy Density ◽  
Power Performance ◽  
Regular Waves ◽  
Wide Range ◽  
Tidal Turbine ◽  
Blade Tip

Tidal energy has the advantages of high predictability, high energy density, and limited environmental impacts. As tidal turbines are expected to be used in the most energetic waters where there might be significant waves, the assessment of unsteady hydrodynamic load due to surface waves is of great concern. The objective of this paper is to assess the effects of surface waves and submergence of the turbine on the power performance and loads of a tidal turbine by experimental approach. The experiments on a 1 : 25th model tidal turbine were carried out in a towing tank. A wide range of regular waves with periods from 1.0 s to 3.0 s at model scale were generated. Different submergence conditions were considered to investigate the effects of the presence of free surface. The cases with blade tip partly going out of water were also performed. The regular waves did not have significant influences on average loads and power output in the present experiments, but caused large amplitude of the cyclic variation of the loads. The amplitudes of the cyclic load were proved to be proportional to the incident wave height, and to be sensitive to the wave frequency and submergence of the rotor. As the tidal turbine getting close to free surface, significant waves were induced by the underwater rotating blade. The effects of surface waves and submergence need to be taken into account in design.

Numerical modelling of free surface dynamics of conductive melt in induction crucible furnace

2010 ◽  
Vol 46 (4) ◽  
pp. 425-436 ◽  
Author(s):  
S. Spitans ◽  
A. Jakovičs ◽  
E. Baake ◽  
B. Nacke
Keyword(s):  
Free Surface ◽  
Numerical Modelling ◽  
Surface Dynamics ◽  
Crucible Furnace ◽  
Free Surface Dynamics

scholarly journals Experimental and Computational Approach to Fatigue Behavior of Polycrystalline Tantalum

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 416 ◽  
Author(s):  
Damien Colas ◽  
Eric Finot ◽  
Sylvain Flouriot ◽  
Samuel Forest ◽  
Matthieu Mazière ◽  
...  
Keyword(s):  
Free Surface ◽  
Low Cycle Fatigue ◽  
Large Strain ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Field Measurements ◽  
Test Sample ◽  
Lattice Rotation ◽  
Element Simulation ◽  
Crack Initiation Criterion

This work provides an experimental and computational analysis of low cycle fatigue of a tantalum polycrystalline aggregate. The experimental results include strain field and lattice rotation field measurements at the free surface of a tension–compression test sample after 100, 1000, 2000, and 3000 cycles at ±0.2% overall strain. They reveal the development of strong heterogeneites of strain, plastic slip activity, and surface roughness during cycling. Intergranular and transgranular cracks are observed after 5000 cycles. The Crystal Plasticity Finite Element simulation recording more than 1000 cycles confirms the large strain dispersion at the free surface and shows evidence of strong local ratcheting phenomena occurring in particular at some grain boundaries. The amount of ratcheting plastic strain at each cycle is used as the main ingredient of a new local fatigue crack initiation criterion.

scholarly journals The high current experiment: First results

2002 ◽  
Vol 20 (3) ◽  
pp. 435-440 ◽  
Author(s):  
P.A. SEIDL ◽  
D. BACA ◽  
F.M. BIENIOSEK ◽  
A. FALTENS ◽  
S.M. LUND ◽  
...  
Keyword(s):  
Space Charge ◽  
Ion Beam ◽  
Beam Steering ◽  
Fusion Energy ◽  
National Laboratory ◽  
Heavy Ion ◽  
High Current ◽  
Current Experiment ◽  
First Results ◽  
High Space

The High Current Experiment (HCX) is being assembled at Lawrence Berkeley National Laboratory as part of the U.S. program to explore heavy ion beam transport at a scale representative of the low-energy end of an induction linac driver for fusion energy production. The primary mission of this experiment is to investigate aperture fill factors acceptable for the transport of space-charge dominated heavy ion beams at high space-charge intensity (line-charge density ∼ 0.2 μC/m) over long pulse durations (>4 μs). This machine will test transport issues at a driver-relevant scale resulting from nonlinear space-charge effects and collective modes, beam centroid alignment and beam steering, matching, image charges, halo, lost-particle induced electron effects, and longitudinal bunch control. We present the first experimental results carried out with the coasting K+ ion beam transported through the first 10 electrostatic transport quadrupoles and associated diagnostics. Later phases of the experiment will include more electrostatic lattice periods to allow more sensitive tests of emittance growth, and also magnetic quadrupoles to explore similar issues in magnetic channels with a full driver scale beam.

scholarly journals Experimental analysis of the shear flow effect on tidal turbine blade root force from three-dimensional mean flow reconstruction

2020 ◽  
Vol 378 (2178) ◽  
pp. 20200001 ◽  
Author(s):  
B. Gaurier ◽  
Ph. Druault ◽  
M. Ikhennicheu ◽  
G. Germain
Keyword(s):  
Turbine Blade ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Tidal Energy ◽  
Velocity Shear ◽  
Reconstruction Method ◽  
Mean Flow ◽  
Blade Root ◽  
Image Velocimetry ◽  
Tidal Turbine

In the main tidal energy sites like Alderney Race, turbulence intensity is high and velocity fluctuations may have a significant impact on marine turbines. To understand such phenomena better, a three-bladed turbine model is positioned in the wake of a generic wall-mounted obstacle, representative of in situ bathymetric variation. From two-dimensional Particle Image Velocimetry planes, the time-averaged velocity in the wake of the obstacle is reconstructed in the three-dimensional space. The reconstruction method is based on Proper Orthogonal Decomposition and enables access to a representation of the mean flow field and the associated shear. Then, the effect of the velocity gradient is observed on the turbine blade root force, for four turbine locations in the wake of the obstacle. The blade root force average decreases whereas its standard deviation increases when the distance to the obstacle increases. The angular distribution of this phase-averaged force is shown to be non-homogeneous, with variation of about 20% of its time-average during a turbine rotation cycle. Such force variations due to velocity shear will have significant consequences in terms of blade fatigue. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.

scholarly journals Passive acoustic methods for tracking the 3D movements of small cetaceans around marine structures

2020 ◽  
Author(s):  
Douglas Gillespie ◽  
Laura Palmer ◽  
Jamie Macaulay ◽  
Carol Sparling ◽  
Gordon Hastie
Keyword(s):  
Marine Mammals ◽  
New Technologies ◽  
Three Dimensional ◽  
Tidal Energy ◽  
Time Of Arrival ◽  
Marine Animals ◽  
Tidal Turbines ◽  
Wide Range ◽  
Tidal Turbine ◽  
Passive Acoustic

AbstractA wide range of anthropogenic structures exist in the marine environment with the extent of these set to increase as the global offshore renewable energy industry grows. Many of these pose acute risks to marine wildlife; for example, tidal energy generators have the potential to injure or kill seals and small cetaceans through collisions with moving turbine parts. Information on fine scale behaviour of animals close to operational turbines is required to understand the likely impact of these new technologies. There are inherent challenges associated with measuring the underwater movements of marine animals which have, so far, limited data collection. Here, we describe the development and application of a system for monitoring the three-dimensional movements of cetaceans in the immediate vicinity of a subsea structure. The system comprises twelve hydrophones and software for the detection and localisation of vocal marine mammals. We present data demonstrating the systems practical performance during a deployment on an operational tidal turbine between October 2017 and October 2019. Three-dimensional locations of cetaceans were derived from the passive acoustic data using time of arrival differences on each hydrophone. Localisation accuracy was assessed with an artificial sound source at known locations and a refined method of error estimation is presented. Calibration trials show that the system can accurately localise sounds to 2m accuracy within 20m of the turbine but that localisations become highly inaccurate at distances greater than 35m. The system is currently being used to provide data on rates of encounters between cetaceans and the turbine and to provide high resolution tracking data for animals close to the turbine. These data can be used to inform stakeholders and regulators on the likely impact of tidal turbines on cetaceans.

Numerical Modelling of the Heat and Mass Transfer in a Channel with Hygroscopic Walls

2008 ◽  
Vol 273-276 ◽  
pp. 782-788 ◽  
Author(s):  
C.R. Ruivo ◽  
J.J. Costa ◽  
A.R. Figueiredo
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Numerical Modelling ◽  
Heat And Mass Transfer ◽  
Sorption Isotherms ◽  
Physical Modelling ◽  
Desorption Process ◽  
Strongly Coupled ◽  
Two Phases ◽  
Adsorption Desorption

In this paper the numerical modelling of the behaviour of a channel of a hygroscopic compact matrix is presented. The heat and mass transfer phenomena occurring in the porous medium and within the airflow are strongly coupled, and some properties of the airflow and of the desiccant medium exhibit important changes during the sorption/desorption processes. The adopted physical modelling takes into account the gas side and solid side resistances to heat and mass transfer, as well as the simultaneous heat and mass transfer together with the water adsorption/desorption process in the wall domain. Two phases co-exist in equilibrium inside the desiccant porous medium, the equilibrium being characterized by sorption isotherms. The airflow is treated as a bulk flow, the interaction with the wall being evaluated by using appropriated convective coefficients. The model is used to perform simulations considering two distinct values of the channel wall thickness and different lengths of the channel. The results of the modelling lead to a good understanding of the relationship between the characteristics of the sorption processes and the behaviour of hygroscopic matrices, and provide guidelines for the wheel optimization, namely of the duration of the adsorption and desorption periods occurring in each hygroscopic channel.

From Bulbous Bow to Free-Surface Shock Wave—Trends of 20 Years’ Research on Ship Waves at the Tokyo University Tank

1981 ◽  
Vol 25 (03) ◽  
pp. 147-180
Author(s):  
Takao Inui
Keyword(s):  
Shock Wave ◽  
Free Surface ◽  
Field Measurements ◽  
Wave Pattern ◽  
Ship Waves ◽  
Second Stage ◽  
Initial Stage ◽  
Man And Nature ◽  
Bulbous Bow ◽  
The Relationship

Trends of 20 years' research on ship waves at the Tokyo University Tank since 1960 are briefly sketched. Stress is focused on the importance of dialogues between man and nature. The process of these dialogues is exemplified by some typical cases, including the development of bulbous bows and the finding of free-surface shock waves. Wave-pattern pictures are shown to be indispensable for the initial stage of the di alogues, while wave contours and velocity-field measurements serve well in the second stage. The current wave analysis and wake survey may be the third. The relationship between "wavebreaking" and the "free-surface shock wave" is also discussed.

Sign in / Sign up

Export Citation Format

Share Document