scholarly journals Characteristics of the Near-Ground Typhoon Morakot

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yanru Wang ◽  
Yongguang Li ◽  
Bin Fu ◽  
Xu Wang ◽  
Chuanxiong Zhang ◽  
...  
Keyword(s):  
Wind Speed ◽  
Density Distribution ◽  
Probability Density ◽  
Probability Density Distribution ◽  
Autocorrelation Coefficient ◽  
Typhoon Morakot ◽  
Mean Wind Speed ◽  
The Mean ◽  
Fluctuating Wind ◽  
Good Agreement

Two WJ-3 anemometers placed at the same height on the top of an architectural engineering building in Wenzhou University are used to determine the wind speed of Typhoon Morakot during its landing in real time. This study aims to explore Typhoon Morakot’s wind field characteristics, including mean wind speed, probability density distribution of fluctuating wind speed, power spectral density, correlation analysis, and coherence, on the basis of data measured by the two anemometers. Results show that the probability density distribution of the fluctuating wind speed of the typhoon follows the Gaussian distribution, and the measured cross-power spectrum of fluctuating wind speed is in good agreement with the modified Karman spectrum. The autocorrelation decreases with the increase in time interval (τ). The longitudinal autocorrelation coefficient decays rapidly with the increase in τ, and the lateral autocorrelation coefficient decays at an unchanged rate. The exponential attenuation coefficients of the longitudinal and transverse fluctuating wind speeds increase with the increase in the mean wind speed, and their mean values are 10.86 and 15.33, respectively. The change trends of the coherence coefficients of the two wind speed components with the mean wind speed are the same. The measured coherence coefficients of the two wind speed components are in good agreement with the exponential function.

Characteristics of the Mean Wind Speed Based on Field Measurement at Aizhai Bridge Gorge

2014 ◽  
Vol 521 ◽  
pp. 113-116
Author(s):  
Hong Xin Sun ◽  
Tao Yu ◽  
Xiu Yong Wang
Keyword(s):  
Surface Roughness ◽  
Wind Speed ◽  
Field Measurement ◽  
Bridge Site ◽  
Design Code ◽  
Average Wind Speed ◽  
Average Wind ◽  
Mean Wind Speed ◽  
The Mean ◽  
Fluctuating Wind

It is seriously different about characteristics of the mean wind speed between a deep gorge and plains, because of the deck of Aizhai bride to deep gorge bottom up to 335m. Characteristics of the mean wind speed in the deep gorge at the Aizhai bridge site are investigated based on field measurement using three 2D anemometers. The plan of field measurement was induced, and the wind speed, fluctuating wind speed and the 10min average wind speed with 10 days as a unit was analyzed. It if found that wind direction is basically consistent with the gorge toward. Based on the Wind-Resistant Design code, the surface roughness coefficients was fitted about 0.29, and very close to D class of the wind code.

On the Relation Between the Factor of Safety and Reliability

1974 ◽  
Vol 96 (3) ◽  
pp. 853-857 ◽  
Author(s):  
My Dao-Thien ◽  
M. Massoud
Keyword(s):  
Density Distribution ◽  
Probability Density ◽  
Coefficient Of Variation ◽  
Factor Of Safety ◽  
Mean Value ◽  
Probability Density Distribution ◽  
Approximate Relation ◽  
Safety And Reliability ◽  
The Mean ◽  
Function Relationship

An approximate relation between the reliability of a design and the classical deterministic factor of safety, used in the design, is presented. An expression of the reliability as function of the mean value and coefficient of variation of the probability density distribution of the factor of safety, is derived. Further, the relation between the deterministic factor of safety and the statistical values of the probabilistic factor of safety, is discussed. Finally an expression for the reliability as a function of the deterministic factor of safety and the parameters determining the stress and strength distributions, is obtained. This function relationship is expressed in a design nomogram relating all the parameters involved.

Scale and Lag Effects on Control of Aerodynamic Power and Loads on a HAWT Rotor

2001 ◽  
Vol 123 (4) ◽  
pp. 339-345 ◽  
Author(s):  
P. J. Moriarty ◽  
A. J. Eggers, ◽  
K. Chaney ◽  
W. E. Holley
Keyword(s):  
Control System ◽  
Fatigue Life ◽  
Wind Speed ◽  
Open Loop ◽  
Time Lags ◽  
Large Power ◽  
Lag Effects ◽  
Mean Wind Speed ◽  
The Mean ◽  
High Control

The effects of rotor scale and control system lag were examined for a variable-speed wind turbine. The scale study was performed on a teetered rotor with radii ranging between 22.5m and 33.75m. A 50% increase in radius more than doubled the rated power and annual energy capture. Using blade pitch to actively control fluctuating flatwise moments allowed for significant reductions in blade mass for a fixed fatigue life. A blade operated in closed-loop mode with a 33.75m radius weighed less than an open-loop blade with a 22.5m radius while maintaining the same fatigue life of 5×109 rotations. Actuator lag reduced the effectiveness of the control system. However, 50% reductions in blade mass were possible even when implementing a relatively slow actuator with a 1 sec. time constant. Other practical limits on blade mass may include fatigue from start/stop cycles, non-uniform turbulence, tower wake effects, and wind shear. The more aggressive control systems were found to have high control accelerations near 60 deg/s2, which may be excessive for realistic actuators. Two time lags were introduced into the control system when mean wind speed was estimated in a rapidly changing wind environment. The first lag was the length of time needed to determine mean wind speed, and therefore the mean control settings. The second was the frequency at which these mean control settings were changed. Preliminary results indicate that quickly changing the mean settings (every 10 seconds) and using a moderate length mean averaging time (60 seconds) resulted in the longest fatigue life. It was discovered that large power fluctuations occurred during open-loop operation which could cause sizeable damage to a realistic turbine generator. These fluctuations are reduced by one half or more when aerodynamic loads are actively controlled.

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