Nowadays,concerns arise because of the depletion of fossil fuel resources that forced scientists to develop new energy extraction methods.One of these renewable resources is tidal energy,where Iran has this potential ...Nowadays,concerns arise because of the depletion of fossil fuel resources that forced scientists to develop new energy extraction methods.One of these renewable resources is tidal energy,where Iran has this potential significantly.There are many ways to obtain the kinetic energy of the fluid flow caused by the moon’s gravitational effect on seas.Using horizontal axis tidal turbines is one of the ways to achieve the kinetic energy of the fluid.Since this type of turbine has similar technology to horizontal axis wind turbines,they may be an appropriate choice for constructing a tidal power plant in Iran.This paper presents the numerical simulation and momentum method of a three-bladed horizontal axis tidal turbine.To validate the thrust and power coefficients for a fixed pitch angle at the blade tip speed ratio of 4 to 10 are compared with experimental results.In this modelling,the rotating geometry simulation has been used.Results show that using a numerical method and blade element momentum,we can predict the horizontal axis tidal turbine’s thrust with an error of less than 10%.The numerical method has better accuracy in higher speed ratios,and it is appropriate to predict the behaviour of fluid in collision with turbines and its wake effects.展开更多
Marine turbines have been extensively utilized to harness tidal stream energy from free-flowing tides and currents. However, the assessment of the influences of these marine structures on the surrounding environment i...Marine turbines have been extensively utilized to harness tidal stream energy from free-flowing tides and currents. However, the assessment of the influences of these marine structures on the surrounding environment is still in its early stage. In this study, a numerical model that couples hydrodynamics and sediment transport is developed to simulate the scour processes around a monopile-supported horizontal axial tidal stream turbine under steady currents. The flow characteristics are calculated by solving the 3-D Navier-Stokes equations with the k -ω shear stress transport (SST) turbulence model for closure. The simulation of sediment bed elevation is achieved by solving the Exner equation. The turbine rotor is parameterized using the actuator line method. The developed model is validated against wake velocity and scour depth measurement obtained from previous literature, showing a good agreement. Subsequently, the effects of tip clearance on the flow characteristics around the turbine model on a rigid flatbed are examined. Finally, the scour processes of the turbine model are presented, along with the vortex system within the scour hole. The numerical model proposed in this study has the potential to contribute to the understanding of the scour mechanism of the tidal stream turbines.展开更多
In the past decade, the tidal energies have caused worldwide concern as it can provide regular and predictable re- newable energy resource for power generation. The majority of technologies for exploiting the tidal st...In the past decade, the tidal energies have caused worldwide concern as it can provide regular and predictable re- newable energy resource for power generation. The majority of technologies for exploiting the tidal stream energy are based on the concept of the horizontal axis propellers, which can be derived from the design and operation of wind turbines. However, there are some peculiar features such as the propeller working in the seawater with free surface and the possible occurrence of cavitation as compared with wind turbines. Especially, for a coun- ter-rotating type tidal stream power turbine, it is difficult to accurately predict the interaction between the front and rear blades at the design stage by blade element momentum theory. As a result, CFD shows its advantage to predict the performance of counter-rotating type propellers of the tidal stream turbi^le. In order to improve the accuracy of CFD predictions, the predicted results must be verified with experimental values. In this paper, a CFD model using block-structured grid was set up and experimental test was performed in a water tunnel for a tidal stream turbine with counter-rotating type propellers. The comparison between CFD predictions and experimental data shows quite good agreement on the power coefficients, which provides an evidence of validation of the CFD model. Such results offer the necessary confidence in the accuracy of the set up CFD model for the coun- ter-rotating type tidal stream turbine.展开更多
文摘Nowadays,concerns arise because of the depletion of fossil fuel resources that forced scientists to develop new energy extraction methods.One of these renewable resources is tidal energy,where Iran has this potential significantly.There are many ways to obtain the kinetic energy of the fluid flow caused by the moon’s gravitational effect on seas.Using horizontal axis tidal turbines is one of the ways to achieve the kinetic energy of the fluid.Since this type of turbine has similar technology to horizontal axis wind turbines,they may be an appropriate choice for constructing a tidal power plant in Iran.This paper presents the numerical simulation and momentum method of a three-bladed horizontal axis tidal turbine.To validate the thrust and power coefficients for a fixed pitch angle at the blade tip speed ratio of 4 to 10 are compared with experimental results.In this modelling,the rotating geometry simulation has been used.Results show that using a numerical method and blade element momentum,we can predict the horizontal axis tidal turbine’s thrust with an error of less than 10%.The numerical method has better accuracy in higher speed ratios,and it is appropriate to predict the behaviour of fluid in collision with turbines and its wake effects.
基金Project supported by the National Key Research and Development Program of China(Grant No.2023YFB4204102)the National Outstanding Youth Science Fund Project(Grant No.52122109)+1 种基金the Key Project of NSFC-Shandong Joint Research Funding POW3C(Grant No.U1906230)the Project Funded by China Postdoctoral Science Foundation(Grant No.2023M730930).
文摘Marine turbines have been extensively utilized to harness tidal stream energy from free-flowing tides and currents. However, the assessment of the influences of these marine structures on the surrounding environment is still in its early stage. In this study, a numerical model that couples hydrodynamics and sediment transport is developed to simulate the scour processes around a monopile-supported horizontal axial tidal stream turbine under steady currents. The flow characteristics are calculated by solving the 3-D Navier-Stokes equations with the k -ω shear stress transport (SST) turbulence model for closure. The simulation of sediment bed elevation is achieved by solving the Exner equation. The turbine rotor is parameterized using the actuator line method. The developed model is validated against wake velocity and scour depth measurement obtained from previous literature, showing a good agreement. Subsequently, the effects of tip clearance on the flow characteristics around the turbine model on a rigid flatbed are examined. Finally, the scour processes of the turbine model are presented, along with the vortex system within the scour hole. The numerical model proposed in this study has the potential to contribute to the understanding of the scour mechanism of the tidal stream turbines.
基金cosponsored by the New Energy and Industrial Technology Development Organization in JapanResearch Project: Grant-in-aid for Science Research C in Japan (2012-2014)
文摘In the past decade, the tidal energies have caused worldwide concern as it can provide regular and predictable re- newable energy resource for power generation. The majority of technologies for exploiting the tidal stream energy are based on the concept of the horizontal axis propellers, which can be derived from the design and operation of wind turbines. However, there are some peculiar features such as the propeller working in the seawater with free surface and the possible occurrence of cavitation as compared with wind turbines. Especially, for a coun- ter-rotating type tidal stream power turbine, it is difficult to accurately predict the interaction between the front and rear blades at the design stage by blade element momentum theory. As a result, CFD shows its advantage to predict the performance of counter-rotating type propellers of the tidal stream turbi^le. In order to improve the accuracy of CFD predictions, the predicted results must be verified with experimental values. In this paper, a CFD model using block-structured grid was set up and experimental test was performed in a water tunnel for a tidal stream turbine with counter-rotating type propellers. The comparison between CFD predictions and experimental data shows quite good agreement on the power coefficients, which provides an evidence of validation of the CFD model. Such results offer the necessary confidence in the accuracy of the set up CFD model for the coun- ter-rotating type tidal stream turbine.
