Zhengnong Li

Wind pressure and wind-induced vibration of heliostat

Heliostat is the key part of Solar Tower power station, which requires extremely high accuracy in use. But it’s sensitive to gust because of its light structure, so effect of wind load should be taken into account in design. Since structure of heliostat is unusual and different from common ones, experimental investigation on rigid heliostat model using technology of surface pressure mensuration to test 3-dimensional wind loads in wind tunnel was conducted. The paper illustrates distribution and characteristics of reflector’s mean and fluctuating wind pressure while wind direction angle varied from 0° to 180° and vertical angle varied from 0° to 90°. Moreover, a finite element model was constructed to perform calculation on wind-induced dynamic response. The results show that the wind load power spectral change rulers are influenced by longitudinal wind turbulence and vortex and are related with Strouhal number; the fluctuating wind pressures between face and back mainly appear positive correlation, and the correlation coefficients at longitudinal wind direction are smaller than those at lateral direction; the fluctuating wind pressures preferably agree with Gaussian distribution at smaller vertical angle and wind direction angle. The wind-induced response and its spectrums reveal that: when vertical angle is small, the background responsive values of reflector’s different parts are approximately similar; in addition, multi-phased resonant response occurring at the bottom. With the increase of , airflow separates at the near side and reunites at the other, as produces vortex which enhances dynamic response at the upper part.

Wind Dynamics Testing on Dahan Heliostat

The aperture area of DAHAN heliostat is 100m2, and the center of drive mechanism is 7m above the ground. The purpose of this study is to provide wind load reference for the structural design of heliostat by means of wind turnnel test. The test mainly consisted of the measurement of time-history wind pressure on heliostat model under various operating conditions of vertical and horizontal wind direction, and the measurement of forces and moments of heliostat with wind tunnel balance. On the basis of data processing and calculation, mean wind pressure coefficient, root-mean-square wind pressure coefficient and the maximum wind pressure of each test point and blockage were obtained in the wind speed of 14m/s, which are used to calculate the possible maximum displacement and strain of the heliostat structure.

Research on Numerical Simulation of Heliostat's Surface Wind Pressure

Heliostat is the major part of solar tower power station whose wind resistance is deemed significant in design. The CFD model of single heliostat under typical operating situation was founded by technology of numerical simulation based on standard k-ε model. This paper puts forward a mesh generation method applied to complex projects under different working conditions. The corresponding UDF program was framed & used to simulate proper wind field entry conditions. The wind pressure distributions variation rules at different wind direction & elevation angles got summarized. The drag coefficients, the lift coefficients, and the three-dimensional moment coefficients in wind power coordinate under different operating conditions were computed. The results agree well with experimental data though a little bigger error exists locally. Moreover, the flow field distribution hard to acquire in wind tunnel test was compensated to further explain origin of heliostats wind pressure distribution. The influencing factors and the variation rules discovered reveals that prediction by numerical simulation is practically satisfactory.

Full-Scale Measurements of Typhoon Effects on a Super RC Tall Building Based on a Remote Monitoring System

This paper presents the field measurement results of wind effects on the world’s tallest reinforced concrete building (CITIC Plaza, 391 m high) located in Guangzhou during the passage of typhoon Pabuk on August 10, 2007. The field data such as wind speed, wind direction and acceleration responses were simultaneously and continuously recorded from the tall building by a remote monitoring system. Detailed analysis of the field data was carried out to investigate the wind effects on the super tall building. The characteristics of the typhoon-generated wind including turbulence intensity, gust factor, turbulence integral length scale and power spectral density of fluctuating wind speed were analyzed. The dynamic characteristics of the buildings were determined from the field measurements and comparison with those calculated from the computational model of the building was made. The measured natural frequencies of the two fundamental sway modes of the building were found to be larger than those calculated. The damping ratios of the building were evaluated by random decrement technique, which demonstrated obvious amplitude-dependent characteristics and increased with increasing amplitude of the building during Typhoon Pabuk.