Performance Of Downstream Wind Turbine Research Articles

Wake interaction between two spar-type floating offshore wind turbines under different layouts

Limited by layout space and manufacturing costs, wake interaction in offshore wind farms is inevitable and can have adverse effects on the performance of downstream wind turbines. To gain a better understanding of the wake interaction between Floating Offshore Wind Turbines (FOWTs), this paper conducts coupled aero-hydrodynamic simulations for two spar-type FOWTs under different layouts. The Unsteady Actuator Line Model (UALM) is used to analyze the unsteady aerodynamic loads of the wind turbine, while the hydrodynamic responses of the floating support platform are obtained using the Computational Fluid Dynamics (CFD) method. To predict the aero-hydrodynamic performance of the FOWT under combined wind and waves, an in-house CFD code developed at Shanghai Jiao Tong University (SJTU), called FOWT-UALM-SJTU solver, is utilized. First, grid convergence test and time step sensitivity study are performed to determine appropriate simulation parameters. Subsequently, numerical simulations of two FOWTs under tandem and offset layouts are conducted to investigate the influence of wake interaction on the performance of downstream FOWT. The dynamic responses of the FWOT, including aerodynamic loads, platform motions, and wake characteristics, are analyzed in detail. From the simulation results and discussions, several conclusions are drawn. Both platform motions and wake interaction contribute to an increased variation range of inflow wind speed experienced by the downstream FOWT, thereby exacerbating the instability of its aerodynamic loads. Under the tandem layout, the platform motions of the upstream FOWT and the downstream FOWT exhibit opposite effects on the aerodynamic loads of the downstream FOWT. Moreover, platform motions increase turbulence intensity in the wake region, accelerating wake velocity recovery and widening the wake width.

CFD Studies of Wake Characteristics and Power Capture of Wind Turbines With Trailing Edge Flaps

Trailing edge flap (TEF) devices will change downstream wake development in wind farms comprising smart rotors, which in turn affect the performance of downstream wind turbines. To study the influence of TEFs on downstream wake development and power capture of wind turbines in wind farms, computational fluid dynamics (CFD) simulations using the three-dimensional rotor model are performed in this paper. The CFD software Fluent is adopted to simulate a wind farm with two tandem wind turbines with TEFs at rated and below rated turbulent wind conditions. Under the 11.4 m/s turbulent wind conditions, the results show that the deflection of the TEF increases the velocity deficit and reduces the wake width, making the wake more complicated. And the positive TEF angle has a greater influence on downstream wake than the negative TEF angle. Additionally, under the 9 m/s turbulent wind conditions, the total power of the two wind turbines increases by 6.5% when the TEF angles are 6°.

Numerical simulations on the wake effect of H-type vertical axis wind turbines

The wake of a wind turbine has substantial influence on the aerodynamic performance of downstream wind turbine. Unsteady numerical simulations are performed in this paper to investigate the wake structure of a three-bladed H-type VAWT (vertical axis wind turbine) and the influence on the aerodynamic performance of downstream wind turbine. A simplified two-dimensional model is used considering the blades are straight. Unsteady Reynolds Averaged Navier–Stokes equations are solved using FlowVision software, which uses dynamic grid method to handle the blade rotation. The SST turbulence model is used for turbulence modeling. The distance between two wind turbines is from 5D to 17D with 2D intervals, where D denotes the wind turbine diameter. The wind speed is 5.07 m/s, corresponding to a tip speed ratio of 2.15. The power coefficients of two wind turbines are compared in detail. The discussions focus on the periodic variations of the aerodynamic performance and flow variables of two turbines with two typical distances, i.e., 7D and 15D, respectively. The simulation results show that the velocity recovery distance needed for a VAWT is usually larger than 15D.

Numerical Simulation of the Wake Effect of a H-Type Wind Turbine on Downstream Wind Turbine

The unsteady wake effect of upstream wind turbine on the aerodynamic performance of downstream wind turbine is investigated using CFD simulations in this paper with two two-dimensional models of H-type wind turbine of three same blades. Dynamic grids based on the inertial coordinate system are employed and the SST turbulence model is used for turbulence modeling. The wind speed is 5.07 m/s and the tip speed ratio is 2.15. The distance between upstream and downstream wind turbine is 5D, 7D, 9D, 11D, 13D, 15D and 17D (D denotes the diameter of the wind turbine). The power coefficient of upstream and downstream wind turbine is comparative analyzed. The variation of the tangential force coefficient of single blade with azimuth and the velocity distribution of different locations of the wind turbine wake are discussed in detail with the distance between upstream and downstream wind turbine of 7D and 15D. In addition, two-dimensional unsteady viscous flow field through velocity contours in one circle is presented.

Effect of Flow Inclination on Wind Turbine Performance

This work examines the effect of flow inclination on the performance of a stand-alone wind turbine and of wind turbines operating in the wakes of upstream turbines. The experimental portion of this work, which includes performance and flowfield measurements, is conducted in the ETH dynamically-scaled wind turbine test facility, with a wind turbine model that can be inclined relative to the incoming flow. The performance of the wind turbine is measured with an in-line torquemeter, and a 5-hole steady-state probe is used to detail the inflow and wake flow of the turbine. Measurements show that over a range of tip-speed ratios of 4–7.5, the power coefficient of a wind turbine with an incoming flow of 15 deg inclination decreases on average by 7% relative to the power coefficient of a wind turbine with a noninclined incoming flow. Flowfield measurements show that the wake of a turbine with an inclined incoming flow is deflected; the deflection angle is approximately 6 deg for an incoming flow with 15 deg inclination. The measured wake profiles are used as inflow profiles for a blade element momentum code in order to quantify the impact of flow inclination on the performance of downstream wind turbines. In comparison to the case without inclination in the incoming flow, the combined power output of two aligned turbines with incoming inclined flow decreases by 1%, showing that flow inclination in complex terrain does not significantly reduce the energy production.