Horizontal Axis Tidal Turbine Hydrofoil Optimization

As a clean and renewable energy that has not been developed on a large scale,tidal energy is attracting more and more attention.It is expected that tidal power will play an increasingly important role in the power market in the future,and tidal turbines will also be widely developed and applied.The turbine blades are one of the core components that obtain tidal energy.Its hydrodynamic performance determines the energy utilization,the load characteristics,the cavitation characteristics as well as the noise level of the tidal turbine.And the most important factor that determines the blades' performance is the shape of the hydrofoil.Therefore,the high-performance hydrofoil is important to improve the turbine capture capability and reduce the blades load.In this paper,the hydrodynamic analysis,optimization design method of the horizontal axis tidal turbine hydrofoil,the design modeling and numerical simulation of horizontal axis tidal turbine are studied.The main researches are as follow:Firstly,carry out CFD simulation of the hydrofoil.Fluent is adopted for numerical simulation,the C-tpye grid is generated by Pointwise.The SST k-? turbulence model based on RANS was used to analyze the hydrodynamic characteristics of the airfoil flow at different angles of attack.Compared with the experimental results,when the angle of attack is small,the results are perfectly matched,and the comprehensive error is less than1.5% while the maximum error is 2.82%.This part mainly provides accurate numerical calibration for airfoil optimization and is an critical step in the process of optimizing platform construction.Then the single-point and multi-point optimization of the hydrofoil is carried out.Surrogate-based optimization method is used to establish single-point and multi-point optimization platform.According to the hydrodynamic requirements of the different cross-sections of the blade,carry out the optimization of the single angle of attack and multiple angles of attack considering with or without cavitation.The objective function has been significantly improved in the absence of cavitation single point optimization,reaching 19.61%,while multi-point optimization compensates for the poor performance of single-point optimized airfoil at high angles of attack.While considering cavitation,The airfoil reduces the area of cavitation significantly near the optimization point.Results show that the performance of the optimized airfoils is excellent,which verifies the effectiveness of the platform.Finally,the hydrodynamic performance of the horizontal axis tidal current turbine is evaluated by numerical simulation.Firstly,a three-dimensional model of the horizontal axis tidal turbine is established,MRF model is applied to simulate the turbine in steady state.The results of the steady state simulation are verified to be correct,reasonable and accurate,and the flow field analysis shows more flow field details.Then,the horizontal axis turbine models are built with the original and the optimized airfoils respectively,and the results show that the optimized model has higher energy utilization efficiency when the tip velocity ratio is small.