Aerodynamic And Wind-induced Effects Of Super-large Cooling Towers Coupled With Medium/small Scale Modes Under Typhoon

With the widespread application of large-capacity and high-parameter generating units,super-large cooling towers whose altitude are heigher than 190 m height limit value in current standard have been gradually constructed.Compared with medium/large cooling towers,the dynamic characteristics of super-large cooling towers above 200 m are more complex,and the non-stationary and non-Gaussian characteristics of the wind pressure on the surface are more significant,resulting in excessive instantaneous extreme wind loads on the tower surface,especially Local or overall wind damage to the cooling tower structure under strong winds(typhoon)occurs from time to time.Compared with the normal wind,the near-surface wind field is more complex under typhoon,and its specific wind profile and landing attenuation effect make the air flow around the cooling tower very disordered,the surface pressure distribution changes significantly,and the dynamic effect of the structure is more prominen.The existing wind-resistant design theories of cooling towers are based on a good state of wind normal limit state,in which the wind environment parameters(gust factor,wind velocity,turbulence intensity and integral scale,pulsating wind spectrum,etc.)mainly for inland monsoon climate,it is difficult to reflect the specificity of the mesoscale typhoon field wind profile of super large cooling tower the influence of the aerodynamic force and stress.In view of this background,taking the world’s highest 210 m high super-large wet cooling tower under construction in the southeast coast of China as the research object,firstly,based on the non-static equilibrium Euler equation model,the mesoscale weather forecasting model is used to perform high-temporal and high-precision simulations of typhoons ―Hagerby‖,―Rammasun‖ and―Hato‖.The simulation results of typhoon path,minimum central pressure and maximum wind speed are compared with the measured results to verify the accuracy of typhoon simulation,and systematically analyzed the distribution rules of the velocity streamline,rainfall,wind speed,and wind direction angle during the entire typhoon landing process.The near-ground wind speed profile at the landing point was obtained by linear least squares fitting.Based on this,the wind field information simulated by WRF model is used as the input of small-scale CFD simulation.The large eddy simulation method is used to compare and study the correlation and coherence differences of the average and pulsating wind pressure distribution,lift resistance coefficient and pulsating wind pressure on the cooling tower surface under the action of typhoon and normal wind,and the distribution mechanism of velocity streamline and turbulent kinetic energy around the cooling tower was also revealed.Finally,the full transient method is used to analyze the wind-induced dynamic response of the cooling tower cylinder-strut-ring foundation integrated model under four calculation conditions.The analysis focuses on the one-dimensional,two-dimensional and The three-dimensional wind vibration coefficients are compared and studied for the static response and stability performance of super-large cooling towers under the action of normal wind,typhoon Hagupit,typhoon Rammasun and typhoon Hato.Through the study,it can be seen that at the landing time,the surface roughness indexes obtained by fitting the landing points under the action of typhoon Hagupit,typhoon Rammasun and typhoon Hato are 0.101,0.114 and 0.090,respectively,which are all smaller than the normal wind(0.12 for class A landform).Compared with the normal wind under the same wind speed,the maximum increases of the surface pressure coefficient and wind vibration coefficient of the super-large cooling tower under the typhoon are 18.05% and 11.62%,respectively;the maximum increases of the internal force response of the tower cylinder,strut and ring foundation base are 6.509%,14.392% and14.889%,respectively;the overall and local stability decreased by 0.040% and 0.179%.Therefore,the influence of typhoon is suggested to be considered in the calculation of aerodynamic force and wind-induced response of super-large cooling towers,but not in the calculation of stability.The main conclusions can provide a reference for the prediction of wind load distribution and structural response of such super-large cooling towers under the action of typhoon,and deepen the understanding of wind field downscaling technology.