A innovative modeling approach to investigate the efficiency of cross flow water turbine farms (original) (raw)
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In order to determine the optimal arrangement of vertical axis cross-flow marine current turbines within hydropower farms, an innovative, simplified, 2D numerical model was developed. It is based on the interaction between incident flow and turbine blades and was implemented in the CFD software COMSOL Multiphysics. The new approach, which couples a macroscopic model of the main turbine with a RANS calculation, using the k-e turbulence model, proved to save a lot of computational effort. The study pointed on the Achard turbine, a new concept of vertical axis cross-flow turbine. Power coefficients (i.e. turbine efficiency) were calculated for different spatial arrangements of Achard turbines within a hydropower farm. Some trends with respect to the near optimal arrangement could thus be obtained.
In order to determine the optimal arrangement of vertical axis cross-flow marine current turbines within hydropower farms, an innovative, simplified, 2D numerical model was developed. It is based on the interaction between incident flow and turbine blades and was implemented in COMSOL Multiphysics. The new approach proved to save a lot of computational effort: it couples a macroscopic non-rotational model of the turbine with a RANS calculation, using the k-\epsilon turbulence model in Rotating Machinery, Transient Analysis. The study pointed on the Achard turbine, a new French concept of vertical axis cross-flow turbine. Power coefficients (turbine efficiency) were calculated for different spatial arrangements of Achard turbines within a power farm. We obtained a near optimal arrangement that ensures the best global efficiency of the farm.
Efficiency of Marine Hydropower Farms Consisting of MultipleVertical Axis Cross-Flow Turbines
This study focuses on the Achard turbine, a vertical axis, cross-flow, marine current turbine module. Similar modules can be superposed to form towers. A marine or river hydropower farm consists of a cluster of barges, each gathering several parallel rows of towers, running in stabilized current. Two-dimensional numerical modelling is performed in a horizontal cross-section of all towers, using FLUENT and COMSOL Multiphysics. Numerical models validation with experimental results is performed through the velocity distribution, depicted by Acoustic Doppler Velocimetry, in the wake of the middle turbine within a farm model. As long as the numerical flow in the wake fits the experiments, the numerical results for the power coefficient (turbine efficiency) are trustworthy. The overall farm efficiency, with respect to the spatial arrangement of the towers, was depicted by 2D modelling of the unsteady flow inside the farm, using COMSOL Multiphysics. Rows of overlapping parallel towers ensu...
This study focuses on the Achard turbine, a French concept of vertical axis, cross-flow, marine current turbine module. The main advantage of such turbines is their modularity: similar modules can be superposed on the same vertical axis, to form towers, with lengths adapted to marine or river current depths, at different locations. A marine or river power farm consists of a cluster of barges, each barge gathering several parallel rows of towers that can be arranged in different configurations. Another advantage of those turbines is their ability to operate irrespective of the water flow direction. The vertical axis cross-flow turbines run in stabilized current, so the flow can be assumed to be almost unchanged in horizontal planes along the vertical z-axis. This assumption allows performing 2D numerical modelling: the computational domain is a cross-section of all towers at a certain z-level. The 2D modelling of the unsteady flow inside such a hydropower farm has been performed using COMSOL Multiphysics, with the ε k turbulence model, to depict the overall efficiency of the farm, with respect to the spatial arrangement of the towers. The efficiency of the turbines increases as the towers get closer to each other, especially on the downstream row.
Inter-influence of the vertical axis, cross-flow, marine current turbines mounted in farms
In order to determine the optimal arrangement of vertical axis, cross-flow, marine current turbines in hydropower farms, an innovative, simplified, 2D numerical model was developed. It is based on the interaction between incident flow and turbine blades and was implemented in the commercial code COMSOL Multiphysics. The new model proved to save a lot of computational effort. Numerical simulations were performed with the k-\epsilon turbulence model, and turbine power coefficients were calculated for different arrangements. Some trends with respect to the optimal (or near optimal) arrangement could thus be obtained.
2D NUMERICAL MODELLING OF THE UNSTEADY FLOW IN THE ACHARD TURBINES MOUNTED IN HYDROPOWER FARMS
2000
The present study pointed on the Achard turbine, a new concept of vertical axis cross-flow turbine. In order to determine the optimal arrangement of such marine current turbines within hydropower farms, two different 2D numerical models were implemented in the CFD software COMSOL Multiphysics 3.4, and Fluent 6.3 respectively, using the ε − k turbulence model. Global farm efficiency was
In order to determine some optimal (or near optimal) horizontal arrangement of vertical axis cross-flow marine current turbines within hydropower farms, an innovative, simplified, 2D numerical model was developed. It is based on the interaction between incident flow and turbine blades and was implemented in COMSOL Multiphysics. The new approach proved to save a lot of computational effort: it couples a macroscopic non-rotational 2D model of the turbine with a RANS calculation, using the turbulence model in Rotating Machinery, Transient Analysis. The study pointed on the Achard turbine, a new French concept of vertical axis cross-flow turbine. Power coefficients (turbine efficiency) were calculated for different spatial arrangements of Achard turbines within a power farm.
A simple hydropower farm model, equipped with 3 Achard turbine modules, aligned on the same row or put in staggered positions, has been built at 1:5 scale, to be tested in water channel. The 2D numerical modelling of the unsteady flow inside that farm model has been performed with COMSOL Multiphysics, using the k-\epsilon turbulence model, in order to depict the overall efficiency of that farm, with respect to the spatial arrangement of the turbines. Due to the confined flow domain, the efficiency of the studied farm model is obviously greater than the efficiency of a similar farm placed in open current.
Numerical modeling of vertical-axis and transverse-flow hydrokinetic turbine in the Loire river
Hydrokinetic turbines can recover the kinetic energy of marine or river currents. The Hydrofluv research and development project (funded by FUI with the support of the Tenerrdis, DERBI and DREAM clusters) aims to demonstrate the feasibility and acceptability of vertical-axis and transverse-flow turbines. Members of the Hydrofluv project, Hydroquest, FOC Transmissions, ERNEO, Biotope, EDF, Artelia and the LEGI laboratory are working both on improving the machines and on a more complete commercial offer (administrative authorizations, impact studies and profitability). Numerical modeling conducted by the LEGI laboratory and Hydroquest has led to the definition of the machine’s characteristics and main parameters. The incorporation of these terms in a larger three-dimensional numerical model has enabled other parameters to be analyzed, such as head loss around the machine (variation in the free surface and current), the interactions between machines and hydrosedimentary impacts. Several academic studies have validated the developments made by comparing the models. The practical application concerns a study of the prototype scheduled to be placed in the Loire at Orleans at the end of 2014. The model accurately represents the impacts of a machine on its environment and has proved to be highly representative compared to more specific local models, which are for the moment two-dimensional and require longer calculation times.
Numerical and experimental investigation of a cross-flow water turbine
Journal of Hydraulic Research, 2016
A numerical and experimental study was carried out for validation of a previously proposed design criterion for a cross-flow turbine and a new semi-empirical formula linking inlet velocity to inlet pressure. An experimental test stand was designed to conduct a series of experiments and to measure the efficiency of the turbine designed based on the proposed criterion. The experimental efficiency was compared to that from numerical simulations performed using a RANS model with a shear stress transport (SST) turbulence closure. The proposed semi-empirical velocity formula was also validated against the numerical solutions for cross-flow turbines with different geometries and boundary conditions. The results confirmed the previous hydrodynamic analysis and thus can be employed in the design of the cross-flow turbines as well as for reducing the number of simulations needed to optimize the turbine geometry.