scholarly journals Cross-Flow Tidal Turbines with Highly Flexible Blades—Experimental Flow Field Investigations at Strong Fluid–Structure Interactions

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 797
Author(s):  
Stefan Hoerner ◽  
Iring Kösters ◽  
Laure Vignal ◽  
Olivier Cleynen ◽  
Shokoofeh Abbaszadeh ◽  
...  
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Cross Flow ◽  
Speed Ratio ◽  
Fluid Structure Interactions ◽  
Dimensional Parameter ◽  
Fluid Structure ◽  
Passive Flow Control ◽  
Tidal Turbines ◽  
Tidal Turbine

Oscillating hydrofoils were installed in a water tunnel as a surrogate model for a hydrokinetic cross-flow tidal turbine, enabling the study of the effect of flexible blades on the performance of those devices with high ecological potential. The study focuses on a single tip-speed ratio (equal to 2), the key non-dimensional parameter describing the operating point, and solidity (equal to 1.5), quantifying the robustness of the turbine shape. Both parameters are standard values for cross-flow tidal turbines. Those lead to highly dynamic characteristics in the flow field dominated by dynamic stall. The flow field is investigated at the blade level using high-speed particle image velocimetry measurements. Strong fluid–structure interactions lead to significant structural deformations and highly modified flow fields. The flexibility of the blades is shown to significantly reduce the duration of the periodic stall regime; this observation is achieved through systematic comparison of the flow field, with a quantitative evaluation of the degree of chaotic changes in the wake. In this manner, the study provides insights into the mechanisms of the passive flow control achieved through blade flexibility in cross-flow turbines.

scholarly journals Passive flow control mechanisms with bioinspired flexible blades in cross-flow tidal turbines

2021 ◽  
Vol 62 (5) ◽  
Author(s):  
Stefan Hoerner ◽  
Shokoofeh Abbaszadeh ◽  
Olivier Cleynen ◽  
Cyrille Bonamy ◽  
Thierry Maître ◽  
...  
Keyword(s):  
Turbine Blades ◽  
Cross Flow ◽  
Tidal Energy ◽  
Control Mechanisms ◽  
Passive Flow Control ◽  
Turbine Efficiency ◽  
Tidal Turbines ◽  
Passive Flow ◽  
Axial Turbines ◽  
The Cost

Abstract State-of-the-art technologies for wind and tidal energy exploitation focus mostly on axial turbines. However, cross-flow hydrokinetic tidal turbines possess interesting features, such as higher area-based power density in array installations and shallow water, as well as a generally simpler design. Up to now, the highly unsteady flow conditions and cyclic blade stall have hindered deployment at large scales because of the resulting low single-turbine efficiency and fatigue failure challenges. Concepts exist which overcome these drawbacks by actively controlling the flow, at the cost of increased mechatronical complexity. Here, we propose a bioinspired approach with hyperflexible turbine blades. The rotor naturally adapts to the flow through deformation, reducing flow separation and stall in a passive manner. This results in higher efficiency and increased turbine lifetime through decreased structural loads, without compromising on the simplicity of the design. Graphic abstract

scholarly journals High-Speed X-ray Stereo Digital Image Correlation for Fluid-Structure Interactions in a Shock Tube

2020 ◽  
Author(s):  
Jeremy James ◽  
Elizabeth M. Jones ◽  
Enrico C. Quintana ◽  
Kyle P. Lynch ◽  
Benjamin R. Halls ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Shock Tube ◽  
Digital Image ◽  
High Speed ◽  
Image Correlation ◽  
Fluid Structure Interactions ◽  
Fluid Structure ◽  
X Ray ◽  
Stereo Digital Image Correlation

Large Motion Visualization and Estimation for Fluid-Structure Simulations

2015 ◽  
Author(s):  
Tzu-Sheng Shane Hsu ◽  
Timothy Fitzgerald ◽  
Vincent Phuc Nguyen ◽  
Balakumar Balachandran
Keyword(s):  
Objective Function ◽  
High Speed ◽  
Flexible Structures ◽  
Three Dimensional ◽  
Optimization Procedure ◽  
Fluid Structure Interactions ◽  
Displacement Fields ◽  
Fluid Structure ◽  
Computational Implementation

Studies of fluid-structure interactions associated with flexible structures such as flapping wings require the capture and quantification of large motions of bodies that may be opaque. As a case study, motion capture of a free flying insect is considered by using three synchronized high-speed cameras. A solid finite element (FE) representation is used as a reference body and successive snapshots in time of the displacement fields are reconstructed via an optimization procedure. One of the original aspects of this work is the formulation of an objective function and the use of shadow matching and strain-energy regularization. With this objective function, the authors penalize the shape differences between silhouettes of the captured images and the FE representation of the deformed body. A similar method with a three-dimensional voxel cloud (VC) reconstruction is also illustrated. Challenges faced in implementing the VC method are discussed and the current computational implementation will also be covered.

Numerical Investigation of an Optimised Horizontal Axis Tidal Stream Turbine

2019 ◽  
Author(s):  
Hassan El Sheshtawy ◽  
Ould el Moctar ◽  
Thomas E. Schellin ◽  
Satish Natarajan
Keyword(s):  
Output Power ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Navier Stokes Equations ◽  
Tidal Turbines ◽  
Tidal Turbine ◽  
Sst Turbulence Model ◽  
Tidal Stream ◽  
Tidal Stream Turbine

Abstract A tidal stream turbine was designed using one of the optimised hydrofoils, whose lift-to-drag ratio at an angle of attack of 5.2 degrees was 4.5% higher than that of the reference hydrofoil. The incompressible Reynolds-averaged Navier Stokes equations in steady state were solved using k-ω (SST) turbulence model for the reference and optimised tidal stream turbines. The discretisation errors and the effect of different y+ values on the solution were analysed. Thrust and power coefficients of the modelled reference turbine were validated against experimental measurements. Output power and thrust of the reference and the optimised tidal turbines were compared. For a tip speed ratio of 3.0, the output power of the optimised tidal turbine was 8.27% higher than that of the reference turbine of the same thrust.

Directed Particle-Laden Micro-Jet for Dental Caries Evacuation (Keynote Paper)

2003 ◽  
Author(s):  
Michael Amitay ◽  
Shayne Kondor ◽  
Scott Herdic ◽  
Steven L. Anderson
Keyword(s):  
Dental Caries ◽  
Flow Field ◽  
Active Control ◽  
High Speed ◽  
Cross Flow ◽  
Jet Flow ◽  
Spreading Rate ◽  
Exit Plane ◽  
Keynote Paper ◽  
The Cross

Active and passive approaches to control the velocity and concentration of a high speed round particle-laden jet are investigated experimentally using a stereo PIV system. Active control of the flow field and the particles’ velocity and concentration fields, via the addition of swirl to the carrier jet, has shown to have a significant effect in altering both phases. Control is also affected by placing passive pins at the jet exit plane, which results in alteration of the velocity in planes across and normal to the pins. Furthermore, the mixing is increased and the spreading rate is modified. Depending on the number of pins used and their azimuthal location, their interaction with the carrier jet flow lead to the modification of the cross-flow shape of the jet and the direction of the flow.

Fluid-Structure Interactions in a Tube Bundle Subject to Cross-Flow. Part A: Porous Medium Approach

2014 ◽  
Author(s):  
Eliott Tixier ◽  
Cédric Béguin ◽  
Stephane Etienne ◽  
Dominique Pelletier ◽  
Alexander Hay ◽  
...  
Keyword(s):  
Porous Medium ◽  
Tube Bundle ◽  
Cross Flow ◽  
Fluid Structure Interactions ◽  
Fluid Structure ◽  
Flow Part

Numerical Study of Performances of Vertical Axis Tidal Turbines

2012 ◽  
Vol 455-456 ◽  
pp. 296-301
Author(s):  
Yan Liu ◽  
Peng Fei Zhao ◽  
Xiao Hui Su ◽  
Guang Zhao
Keyword(s):  
Flow Field ◽  
Turbulent Flows ◽  
Stokes Equations ◽  
Numerical Study ◽  
Vertical Axis ◽  
Negative Influence ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Tidal Turbines ◽  
Central Shaft

Numerical simulations of flows over two-dimensional vertical axis tidal turbines are carried out. Unsteady Reynolds averaged Navier-Stokes Equations are applied to model turbulent flows. Influence of the central shaft and number of blades on flow field and thus performances of turbines are investigated. Performances in terms of torque and power coefficients are obtained for different types of turbines. Results demonstrates that the central shaft has a negative influence on flow field and power coefficients. Solidity and tip speed ratio are two important factors to affect turbine’s performances. This paper provides useful information for future studies.

scholarly journals 3D Simulation with Flow-Induced Rotation for Non-Deformable Tidal Turbines

2021 ◽  
Vol 9 (3) ◽  
pp. 250
Author(s):  
Ilan Robin ◽  
Anne-Claire Bennis ◽  
Jean-Claude Dauvin
Keyword(s):  
Vertical Axis ◽  
Tidal Energy ◽  
Fluid Structure Interactions ◽  
Good Correspondence ◽  
Tidal Turbines ◽  
Tidal Turbine ◽  
Correct Direction ◽  
Convergence Study ◽  
Vertical Axis Tidal Turbine ◽  
Mesh Convergence

The overall potential for recoverable tidal energy depends partly on the tidal turbine technologies used. One of problematic points is the minimum flow velocity required to set the rotor into motion. The novelty of the paper is the setup of an innovative method to model the fluid–structure interactions on tidal turbines. The first part of this work aimed at validating the numerical model for classical cases of rotation (forced rotation), in particular, with the help of a mesh convergence study. Once the model was independent from the mesh, the numerical results were tested against experimental data for both vertical and horizontal tidal turbines. The results show that a good correspondence for power and drag coefficients was observed. In the wake, the vortexes were well captured. Then, the fluid drive code was implemented. The results correspond to the expected physical behavior. Both turbines rotated in the correct direction with a coherent acceleration. This study shows the fundamental operating differences between a horizontal and a vertical axis tidal turbine. The lack of experiments with the free rotation speed of the tidal turbines is a limitation, and a digital brake could be implemented to overcome this difficulty.

scholarly journals Fluid-structure interactions enable passive flow control in real and biomimetic plants

2021 ◽  
Vol 6 (12) ◽  
Author(s):  
Keunhwan Park ◽  
Aude Tixier ◽  
Magnus Paludan ◽  
Emil Østergaard ◽  
Maciej Zwieniecki ◽  
...  
Keyword(s):  
Flow Control ◽  
Fluid Structure Interactions ◽  
Fluid Structure ◽  
Passive Flow Control ◽  
Passive Flow
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