In order to study the influence of blade tower interaction on tower surface noise in wind turbine operation, the surface noise of the horizontal axis wind turbine tower was tested by the surface microphone in the wind tunnel opening experiment section. The influence of tower relative position on noise and surface noise spectrum was analyzed. The results show that with the increase of the relative position of the tower, the surface noise energy decreases, which is only different from other surfaces on the front surface. The maximum increment of sound pressure level on the front and rear surfaces is 0.71R at the relative position of the tower and does not change with wind speed. The surface noise spectrum mainly shows the characteristics of the blade rotating noise, and the energy difference of each measuring point on the left and right surfaces is more obvious than that of the front and rear surfaces in the middle and high-frequency range. The relevant results can provide ideas for the optimization design of wind turbine tower noise.
Aiming at the problem of poor structural stability and reliability of small and medium-sized wind turbine towers, based on a 5kw wind turbine cylindrical tower , the influence of shape parameters of lattice tower on its structural performance is explored and the corresponding lattice tower is designed. The structural performance of the cylindrical tower and lattice tower is analyzed and compared under the cut-out wind speed condition, at same time to verify the feasibility of the lattice tower. The results show that the structural performance of the lattice tower is optimal when the form of the webs is oblique, the angle of the webs is 50°, and the aspect ratio is controlled at 1/4. And the designed lattice tower meets the structural performance. Compared with the cylindrical tower, the forced distribution of the lattice tower is more evenly, the material utilization rate is better, and the stiffness is better.
Rapid real-time monitoring of wheat nitrogen (N) status is crucial for precision N management during wheat growth. In
this study, Multi Lookup Table (Multi-LUT) approach based on the N-PROSAIL model parameters setting at different
growth stages was constructed to estimating canopy N density (CND) in winter wheat. The results showed that the
estimated CND was in line with with measured CND, with the determination coefficient (R2) and the corresponding root
mean square error (RMSE) values of 0.80 and 1.16 g m-2, respectively. Time-consuming of one sample estimation was
only 6 ms under the test machine with CPU configuration of Intel(R) Core(TM) i5-2430 @2.40GHz quad-core. These
results confirmed the potential of using Multi-LUT approach for CND retrieval in winter wheat at different growth
stages and under variables climatic conditions.
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