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In order to increase the wind capture ability of the wind turbine, many research studies on the lift enhancement method of the wind turbine airfoil have been conducted by scholars at home and abroad. An airfoil with tailing edge flaps has a much higher lift-to-drag ratio than an airfoil without trailing edge flaps. Among all the lift enhancement methods of trailing edge flaps, the structure of the wind turbine airfoil with discrete trailing edge flaps is simple, the cost of production is low, and it can easily achieve variable angle control. But the aerodynamic performance of the wind turbine airfoil with traditional discrete trailing edge flaps has not been comprehensively studied, and gaps between the flaps and the airfoil main body has an influence on the aerodynamic performance of the airfoil. So it is necessary to optimize the gap structure and study the aerodynamic performance of the discrete trailing edge flaps with different deflection angles. Taking a wind turbine airfoil S809 as the research object, the structure of the discrete trailing edge flaps was designed, the chord length was set as 1 000 mm, and the gap between the flap and the main body of airfoil was optimized to make the width of gap an even 1 mm. Then the trailing edge flaps model was established. The flap rotates around the rotate center to form a different flap model at different deflect angles, the deflect angles of the flap varied from 0-16°, and the step size was 2. Mesh generation software Gambit s used to generate a model mesh, and the grids near the trailing edge were refined. After comparing the three kinds of grid number models, the grid independence was verified, and the number of a 148000 grid model for a calculating model was determined. The k-ω two equation turbulence model of Commercial software FLUENT was used here to calculate the aerodynamic performance of the airfoil S809 without flaps, and the result was compared with the experimental data. The result showed that when the attack angle is small ,the error of lift coefficient is less than 0.9%, the error of drag coefficient is less than 4.86%, and the pressure coefficient distributions of calculated model is in good agreement with the experimental data. All these data verified that the calculated method was right and reliable. And then the aerodynamic performance of the 10% chord length flaps with different deflection angle under the attack angle of 0° was studied with the same method. The pressure contours, streamline and pressure coefficient distribution around the model with discrete trailing edge flaps were calculated and analyzed theoretically. The result showed that the gaps between the flap and the main body of airfoil were reasonably designed, and that the gaps had little influence on the aerodynamic performance of the airfoil. So the influence of the gaps can be ignored here. The deflect angle of the discrete trailing edge flaps had much influence on the aerodynamic performance of the model. With the increase of the deflect angle, the camber of airfoil was increased, this made the airflow near trailing edge of airfoil deflected downward, the velocity of airflow near the upper surface of airfoil increased, this result in the pressure of the upper surface of airfoil decreased, and the pressure of the lower surface of airfoil decreased, then the pressure difference between the upper and lower surface was also increased, eventually leading to enhancement of the lift coefficient and the lift-to-drag ratio of the airfoil with discrete trailing edge flaps. When the deflection angle was 14°, the lift-to-drag ratio of the airfoil reached the highest. The drag of the airfoil decreased with the increase of attack angle at first and then increased with the increase of attack angle. When the attack angle was 4°, the drag was the smallest. [ABSTRACT FROM AUTHOR]

A binary distributed detection system comprises a bank of local decision makers (LDM's) and a central information processor (the data fusion center, DFC). All LDM's survey a common volume for a binary {[H.sub.0], [H.sub.1]} phenomenon. Each LDM forms a binary decision: it either accepts [H.sub.1] ("target-present") or [H.sub.0] ("target-absent"). The LDM is fully characterized by its performance probabilities (probability of false alarm and probability of detection). The decisions are transmitted to the DFC through noiseless communication channels. The DFC then optimally combines the local decisions to obtain a global decision ("target-present" or "target-absent") which minimizes a Bayesian objective function. Along with the local decisions, the DFC in our architecture remembers and uses its most recent decision in synthesizing each new decision. When operating in a stationary environment, our architecture converges to a steady-state decision in finite time with probability one, and its detection performance during convergence and in steady state is strictly determined. Once convergence is proven, we apply the results to the detection of signals with random phase and amplitude. We further provide a geometric interpretation for the behavior of the system: the unit square of the current ([P.sub.f], [P.sub.d]) known to the DFC is partitioned into polygons, one of which defines a "stopping set" of values. If the current ([P.sub.f], [P.sub.d]) falls into this region, there is no way to leave it, and hence there is no reason to continue testing.

In wind farms, the wake can lead to a loss of output power, and the uneven characteristics of wake can also exacerbate the fatigue load of downstream wind turbine (WT), affecting their operating life. To explore the impact of wake effects on downstream WT, this article proposes a new method for calculating the load of WT wake wind conditions and verifies it. Establishing a 3DJG wake model coupled with improved BEM for wind turbine aerodynamic performance calculation method. The influence of downstream WT operation phase angle and positions of 3D wake on the time-varying aerodynamic characteristics of downstream WTs was discussed from three perspectives: Blade elements on the spanwise, single blade and wind rotor. Results shown that: (1) For the blade element, calculated the shear force in the flapwise direction and the edgewise direction on each blade segment. The overall shear force of blade element in the vertical upward direction of WT blades is significantly greater than that in other directions. The non-uniformity of the wake is not sufficient to change the position of the maximum shear force on the blade. The position of the maximum shear force at each wake position is in the rear segments of the blade; (2) For the single blade, the most severe load fluctuation occurs when it is in the partial wake condition. The period of this fluctuation is 360°. When in full wake condition, the load fluctuation is relatively small, and due to the symmetry of the wake, the load fluctuation period is only 180°. The load standard deviation (SD) of the partial wake condition increases by 51 % compared to the full wake condition. (3) For the wind rotor, different wake positions have a weighty impact on the power loss of the WT rotor. Compared to the incoming shear wind, the power loss at the wake center can reach up to 54.22 %. At the wake boundary, the power loss of the WT is only 5.6 %. The non-uniformity of wake also has a periodic impact on the power output of the entire WT rotor, with the fluctuation period is 120°, and the fluctuation amplitude of no more than 2 %. This article provides a more intuitive quantitative analysis of the impact of wake on the time-varying aerodynamic characteristics of downstream WTs. It has certain reference value for the design strength verification of WTs, as well as the yaw strategy and layout design of wind farms. • Established an improved BEM coupling 3DJG wake model for WT load calculation. • The accuracy the proposed method is verified using experimental and OpenFAST. • The impact of non-uniformity of wake on downstream WTs is demonstrated. • The periodical time-varying aerodynamic characteristics of the WT are considered. • The characteristics is from three aspects: blade element, single blade, and entire rotor. [ABSTRACT FROM AUTHOR]